Γεωπονικό Πανεπιστήμιο Αθηνών, Τμήμα Επιστήμης Φυτικής Παραγωγής, 2022
Dianthus cruentus Griseb. (Caryophyllaceae) is a herbaceous perennial species native to the Balka... more Dianthus cruentus Griseb. (Caryophyllaceae) is a herbaceous perennial species native to the Balkan Peninsula, including Greece, and western Asia. It is a species of great ornamental interest due to its architectural inflorescences and its compact blue-green foliage, particularly resistant to dry and poor soils and attractive to pollinators such as butterflies and bees. In addition, it is a species of medical potential due to its strong antioxidant action.
In the present study, the determination of the appropriate conditions for maximizing the germination of its seeds in both in vitro and in vivo conditions was initially investigated. Two seed lots collected from a native population of the species on Mount Kallidromo, Fthiotida, dry-stored for 0 or 12 months, were used, without any pre-treatment.
Regarding in vitro germination, the seeds were surface sterilized with a 20% commercial bleach water solution for 10 minutes, were then rinsed with distilled water and afterwards were placed in Petri dishes containing ½ MS medium, under 16 h photoperiod from 37.5 μmol m-2 s-1 fluorescent light, at temperatures of 5, 10, 15, 20 or 25 °C. The optimum temperature for seed germination was 15 °C, in which the highest germination ability in both recently collected (98%) and 12-month-old seeds (100 %) was observed. The lowest germination percentages were recorded at the two extreme temperatures of 5 °C and 25 °C, with particularly low values for recently collected seeds (18% and 15%). At all temperatures, minus that of 5 °C, the seeds germinated rapidly (T50 = 2-6 d). The duration of the seeds’ dry storage significantly affected their germination, increasing the germination percentage at the 2 extreme temperatures and demonstrating the positive effect of dry afterripening. As for ex vitro germination, the seeds were placed in pots with a mixture of peat-perlite (1: 1, v/v) and were incubated in growing chambers at temperatures of 15, 20 or 25 °C. The highest germination percentage was observed at 15 °C for both seed lots (97-99%), while the lowest at the temperature of 25 °C (62% and 4% for the 0- and 12-months-old seeds respectively). Germination ability was slightly lower in ex vitro germination, especially at 25 °C.
Furthermore, the micropropagation of the species from explants excised from 2-month-old seedlings was investigated on solid substrates. Substrates containing MS medium and 8 g L-1 agar were used in almost all substages of the proliferation stage, and the effects of cytokinins BA, 2iP and ZEA, with the absence or the presence of auxin NAA, were investigated, using explants derived from non-hyperhydric or hyperhydric shoots. In the initial culture substrates containing 0.1 mg L-1 BA or 0.1 or 0.5 mg L-1 2iP the explants produced shoots at a high percentage (72-87%), but many of these were shown to be hyperhydric, with abnormal morphology and vitreous appearance. The number of hyperhydric shoots and the number of nodes seemed to be higher on substrates containing 2iP, with the largest number of normal shoots (2.3) appearing in the substrate containing 0.1 mg L-1 BA.
During the 1st subculture stage, hyperhydric shoots were observed in bigger numbers in the substrate containing 2iP, while an increase in shoot proliferation and the number of hyperhydric shoots was correlated with the use of hyperhydric explants grown on hormone-free MS substrate. In the 2nd subculture stage, the presence of 0.1 mg L-1 BA yielded the largest number of shoots regardless of the physiology of the explants, while the addition of 0.05 mg L-1 resulted in a significant increase in the number of normal shoots and a reduction in hyperhydricity rates when hyperhydric explants were used. In the 3rd subculture, when explants derived from nonhyperhydric shoots were used the highest value of the multiplication index (4.5) and the maximum number of shoots (3.6) was recorded in MS substrate containing 2 mg L-1 BA. Increasing the concentration of agar to 12 g L-1 produced the largest number of shoots (2.4) when hyperhydric explants were used. In both cases, the highest percentages of hyperhydricity were recorded on MS substrate containing 0.1 mg L-1 ZEA. In contrast, during the 4th subculture, the use of this substrate resulted in the greatest multiplication index value at this stage (4.8).
Overall, the use of MS substrate with 0.1 mg L-1 BA and 0.05 mg L-1 NAA resulted in the highest values of the proliferation index (5.1) regardless of the physiology of the explants used, with its maximum value (5.2) recorded from the culture of hyperhydric explants on MS substrate containing 0.1 mg L-1 BA and 12 g L-1 agar. The presence of phytohormones in the substrates increased the production of callus around the base of the explants, while high concentrations of cytokinins lessened the occurence of roots.
D. cruentus microshoots were rooted in MS or ½ MS substrates in the presence or absence of IBA. The use of MS substrate resulted in lower rooting rates (55-70%) when lower concentrations of IBA were used (0 or 0.1 mg L-1). The optimal concentration of IBA was found to be 0.5 mg L-1 regardless of the multiplication substrate where the microshoots originated or the nutrient medium used in the rooting substrate, with rooting rates of 83-100%, while in some instances a carry over effect, caused by the cytokinin content of the shoot proliferation substrates, was observed on the roots’ number and median length.
The ex vitro acclimatization of the rooted microshoots was completed with a success rate of 91% using a peat:perlite substrate (1:1, v/v). Significant morphological differences were observed between acclimatized plantlets, including differences in stem length and total number of shoots and nodes, which were correlated with the influence of different shoot proliferation and/or rooting substrates, while the presence of IBA during rooting seemed to have an amendable effect on their survival. Finally, the use of an integrated, 60-days-long propagation protocol with shoot proliferation and rooting occurring concurrently in one stage on MS substrates free of PGRs or containing BA or 2iP and NAA produced rooted young plants at a high percentage (88%), which had the maximum observed total number of shoots and nodes and were then successfully acclimatized, surviving at a percentage of 86%.
Scientific area: Horticulture
Keywords: Dianthus cruentus, native ornamental plant, germination ecophysiology, seed germination in vitro, seed germination temperature, seed lot age, dry afterripening, in vitro propagation, solid culture, seedling explant, hyperhydricity, hyperhydric explant, callus induction, in vitro rooting, ex vitro acclimatization, cytokinins, IBA, carry over effect, acclimatized plantlets’ morphology
Cactus (Opuntia ficus-indica) cladodes are a source of dietary fiber, vitamins and antioxidants t... more Cactus (Opuntia ficus-indica) cladodes are a source of dietary fiber, vitamins and antioxidants that could be utilized by the food industry for both their nutritional and technological properties. In the present study, cladodes were dried at 45 • C for 24 h, followed by a 18 h vacuum drying at 45 • C or 60 • C. The dried cladodes were then ground in a grain mill, resulting in two coarse cladode flours (C45 and C60, respectively). A portion of the two flours was further ground with jet mill, yielding two fine flours, J45 and J60, respectively. Color, bulk density, water and oil holding capacities, solubility and dietary fiber content were determined. In addition, rheological properties and sedimentation kinetic of aqueous cladode flour suspensions were evaluated. An increase of insoluble fiber was observed with micro-grinding. All samples exhibited shear thinning behavior, while jet milling led to substantial decrease in apparent viscosity values. Coarse fractions sedimented quickly, achieving almost maximum sedimentation within 10 min, while the micro ground samples sedimented half as fast. In conclusion, particle size significantly alters the technological properties of cladode flour, broadening the range of applications cladodes could be used for.
8th International Symposium on Food Rheology and Structure, Zurich, June 2019, 2019
Recently, there is a growing interest in incorporating cactus cladode flour in foods, in order to... more Recently, there is a growing interest in incorporating cactus cladode flour in foods, in order to improve their nutritional value, while cactus cladode mucilage exhibits potential as a thickener. In the present study, cladodes from Opuntia ficus-indica were dried at 45 oC in a hot air dryer for 24 hours, followed by a 18 hours long drying in a vacuum oven at two different temperatures (45 or 60 oC). The dried cladodes were then ground with two different methods (hammer mill or hammer mill followed by jet mill). The physical and rheological properties of the four flours were studied. Color parameters were affected both by drying and grinding process. Cladode flour aqueous solutions (5% w/v) exhibited a non-Newtonian shear thinning behavior, while micronization with jet mill led to lower apparent viscosity values for the tested shear rate range (0.3-300 s-1). These findings show that micronization of cladode flour deteriorates its thickening capacity.
Γεωπονικό Πανεπιστήμιο Αθηνών, Τμήμα Τεχνολογίας Τροφίμων και Διατροφής του Ανθρώπου, 2019
The objective of this study is to investigate the effects of the drying and grinding treatments o... more The objective of this study is to investigate the effects of the drying and grinding treatments on the physical and technological properties of flour produced from prickly pear cactus stem (Opuntia ficus-indica f. inermis). A lot of previous research has uncovered the striking nutritional and functional value of the plant's stems, which can be mainly attributed to their high content of dietary fiber. At the same time, the presence of mucilage, which is a polysaccharide with hydrocolloidal rheological properties, shows promise as a thickening agent suitable for inclusion in many types of food products. During the experimental procedure 4 samples of cladode flour were produced by combining two different drying processes and two different grinding operations. After being cut up into uniform rectangular pieces, cladodes were predried at a temperature of 45o C in a forced air drying oven and then finally dried in a vacuum oven set up either in 45o C or 60o C. The two distinct batches of dehydraded cactus stem produced were then ground to flour in a hammer mill, and half of the produced flour were reprocessed in a jet mill. Finally, after the final preparation of the 4 samples, analysis of the particles' shape and size, their colour values, solubility, WHC and OHC, moisture and dietary fiber content, and finally, the rheological properties and sedimentation rates of 5% w/v dispersions of them in distilled water, were conducted. Flour samples were separated as coarse and fine flours, showing significant changes in median particle size during grinding. Both processes caused intense changes in the color properties of the flours, with the higher final drying temperature resulting in a slightly heat-degraded product. Moisture and water activity were found to be low enough for the samples to be proclaimed stable and safe from microbial, enzymical and oxidative degradation (0.2 < aw < 0.4), while bulk density reduction was observed during final drying at 60°C. Suspensions of all samples exhibited pseudoplastic behavior and dependence of viscosity on temperature, while reprocessing of the flours in the jet mill was found to alter their rheological properties, possibly due to destruction of the mucilage's structure. Dietary fiber content was found to be extremely high for all samples 13 (> 40%), but no safe conclusions can be drawn for the influence of drying and grinding treatments. Solubility and oil retention capacity were mainly affected by grinding, while the water retention capacity was reduced by increasing the final drying temperature of the cladodes. Finally, all flour suspensions were judged to be extremely unstable during the sedimentation test. Based on the results of the present study, it is evident that both heat treatment during drying and grinding of prickly pear tree significantly affect the physical and technological properties of the resulting flour, while further investigations of the milling techniques and their influence are deemed as necessary. At the same time, the extremely high dietary fiber content, combined with its interesting rheological properties, suggest a possible use for the cladode flour as a texture modifier in functional food and nutraceutical products.
Γεωπονικό Πανεπιστήμιο Αθηνών, Τμήμα Επιστήμης Φυτικής Παραγωγής, 2022
Dianthus cruentus Griseb. (Caryophyllaceae) is a herbaceous perennial species native to the Balka... more Dianthus cruentus Griseb. (Caryophyllaceae) is a herbaceous perennial species native to the Balkan Peninsula, including Greece, and western Asia. It is a species of great ornamental interest due to its architectural inflorescences and its compact blue-green foliage, particularly resistant to dry and poor soils and attractive to pollinators such as butterflies and bees. In addition, it is a species of medical potential due to its strong antioxidant action.
In the present study, the determination of the appropriate conditions for maximizing the germination of its seeds in both in vitro and in vivo conditions was initially investigated. Two seed lots collected from a native population of the species on Mount Kallidromo, Fthiotida, dry-stored for 0 or 12 months, were used, without any pre-treatment.
Regarding in vitro germination, the seeds were surface sterilized with a 20% commercial bleach water solution for 10 minutes, were then rinsed with distilled water and afterwards were placed in Petri dishes containing ½ MS medium, under 16 h photoperiod from 37.5 μmol m-2 s-1 fluorescent light, at temperatures of 5, 10, 15, 20 or 25 °C. The optimum temperature for seed germination was 15 °C, in which the highest germination ability in both recently collected (98%) and 12-month-old seeds (100 %) was observed. The lowest germination percentages were recorded at the two extreme temperatures of 5 °C and 25 °C, with particularly low values for recently collected seeds (18% and 15%). At all temperatures, minus that of 5 °C, the seeds germinated rapidly (T50 = 2-6 d). The duration of the seeds’ dry storage significantly affected their germination, increasing the germination percentage at the 2 extreme temperatures and demonstrating the positive effect of dry afterripening. As for ex vitro germination, the seeds were placed in pots with a mixture of peat-perlite (1: 1, v/v) and were incubated in growing chambers at temperatures of 15, 20 or 25 °C. The highest germination percentage was observed at 15 °C for both seed lots (97-99%), while the lowest at the temperature of 25 °C (62% and 4% for the 0- and 12-months-old seeds respectively). Germination ability was slightly lower in ex vitro germination, especially at 25 °C.
Furthermore, the micropropagation of the species from explants excised from 2-month-old seedlings was investigated on solid substrates. Substrates containing MS medium and 8 g L-1 agar were used in almost all substages of the proliferation stage, and the effects of cytokinins BA, 2iP and ZEA, with the absence or the presence of auxin NAA, were investigated, using explants derived from non-hyperhydric or hyperhydric shoots. In the initial culture substrates containing 0.1 mg L-1 BA or 0.1 or 0.5 mg L-1 2iP the explants produced shoots at a high percentage (72-87%), but many of these were shown to be hyperhydric, with abnormal morphology and vitreous appearance. The number of hyperhydric shoots and the number of nodes seemed to be higher on substrates containing 2iP, with the largest number of normal shoots (2.3) appearing in the substrate containing 0.1 mg L-1 BA.
During the 1st subculture stage, hyperhydric shoots were observed in bigger numbers in the substrate containing 2iP, while an increase in shoot proliferation and the number of hyperhydric shoots was correlated with the use of hyperhydric explants grown on hormone-free MS substrate. In the 2nd subculture stage, the presence of 0.1 mg L-1 BA yielded the largest number of shoots regardless of the physiology of the explants, while the addition of 0.05 mg L-1 resulted in a significant increase in the number of normal shoots and a reduction in hyperhydricity rates when hyperhydric explants were used. In the 3rd subculture, when explants derived from nonhyperhydric shoots were used the highest value of the multiplication index (4.5) and the maximum number of shoots (3.6) was recorded in MS substrate containing 2 mg L-1 BA. Increasing the concentration of agar to 12 g L-1 produced the largest number of shoots (2.4) when hyperhydric explants were used. In both cases, the highest percentages of hyperhydricity were recorded on MS substrate containing 0.1 mg L-1 ZEA. In contrast, during the 4th subculture, the use of this substrate resulted in the greatest multiplication index value at this stage (4.8).
Overall, the use of MS substrate with 0.1 mg L-1 BA and 0.05 mg L-1 NAA resulted in the highest values of the proliferation index (5.1) regardless of the physiology of the explants used, with its maximum value (5.2) recorded from the culture of hyperhydric explants on MS substrate containing 0.1 mg L-1 BA and 12 g L-1 agar. The presence of phytohormones in the substrates increased the production of callus around the base of the explants, while high concentrations of cytokinins lessened the occurence of roots.
D. cruentus microshoots were rooted in MS or ½ MS substrates in the presence or absence of IBA. The use of MS substrate resulted in lower rooting rates (55-70%) when lower concentrations of IBA were used (0 or 0.1 mg L-1). The optimal concentration of IBA was found to be 0.5 mg L-1 regardless of the multiplication substrate where the microshoots originated or the nutrient medium used in the rooting substrate, with rooting rates of 83-100%, while in some instances a carry over effect, caused by the cytokinin content of the shoot proliferation substrates, was observed on the roots’ number and median length.
The ex vitro acclimatization of the rooted microshoots was completed with a success rate of 91% using a peat:perlite substrate (1:1, v/v). Significant morphological differences were observed between acclimatized plantlets, including differences in stem length and total number of shoots and nodes, which were correlated with the influence of different shoot proliferation and/or rooting substrates, while the presence of IBA during rooting seemed to have an amendable effect on their survival. Finally, the use of an integrated, 60-days-long propagation protocol with shoot proliferation and rooting occurring concurrently in one stage on MS substrates free of PGRs or containing BA or 2iP and NAA produced rooted young plants at a high percentage (88%), which had the maximum observed total number of shoots and nodes and were then successfully acclimatized, surviving at a percentage of 86%.
Scientific area: Horticulture
Keywords: Dianthus cruentus, native ornamental plant, germination ecophysiology, seed germination in vitro, seed germination temperature, seed lot age, dry afterripening, in vitro propagation, solid culture, seedling explant, hyperhydricity, hyperhydric explant, callus induction, in vitro rooting, ex vitro acclimatization, cytokinins, IBA, carry over effect, acclimatized plantlets’ morphology
Cactus (Opuntia ficus-indica) cladodes are a source of dietary fiber, vitamins and antioxidants t... more Cactus (Opuntia ficus-indica) cladodes are a source of dietary fiber, vitamins and antioxidants that could be utilized by the food industry for both their nutritional and technological properties. In the present study, cladodes were dried at 45 • C for 24 h, followed by a 18 h vacuum drying at 45 • C or 60 • C. The dried cladodes were then ground in a grain mill, resulting in two coarse cladode flours (C45 and C60, respectively). A portion of the two flours was further ground with jet mill, yielding two fine flours, J45 and J60, respectively. Color, bulk density, water and oil holding capacities, solubility and dietary fiber content were determined. In addition, rheological properties and sedimentation kinetic of aqueous cladode flour suspensions were evaluated. An increase of insoluble fiber was observed with micro-grinding. All samples exhibited shear thinning behavior, while jet milling led to substantial decrease in apparent viscosity values. Coarse fractions sedimented quickly, achieving almost maximum sedimentation within 10 min, while the micro ground samples sedimented half as fast. In conclusion, particle size significantly alters the technological properties of cladode flour, broadening the range of applications cladodes could be used for.
8th International Symposium on Food Rheology and Structure, Zurich, June 2019, 2019
Recently, there is a growing interest in incorporating cactus cladode flour in foods, in order to... more Recently, there is a growing interest in incorporating cactus cladode flour in foods, in order to improve their nutritional value, while cactus cladode mucilage exhibits potential as a thickener. In the present study, cladodes from Opuntia ficus-indica were dried at 45 oC in a hot air dryer for 24 hours, followed by a 18 hours long drying in a vacuum oven at two different temperatures (45 or 60 oC). The dried cladodes were then ground with two different methods (hammer mill or hammer mill followed by jet mill). The physical and rheological properties of the four flours were studied. Color parameters were affected both by drying and grinding process. Cladode flour aqueous solutions (5% w/v) exhibited a non-Newtonian shear thinning behavior, while micronization with jet mill led to lower apparent viscosity values for the tested shear rate range (0.3-300 s-1). These findings show that micronization of cladode flour deteriorates its thickening capacity.
Γεωπονικό Πανεπιστήμιο Αθηνών, Τμήμα Τεχνολογίας Τροφίμων και Διατροφής του Ανθρώπου, 2019
The objective of this study is to investigate the effects of the drying and grinding treatments o... more The objective of this study is to investigate the effects of the drying and grinding treatments on the physical and technological properties of flour produced from prickly pear cactus stem (Opuntia ficus-indica f. inermis). A lot of previous research has uncovered the striking nutritional and functional value of the plant's stems, which can be mainly attributed to their high content of dietary fiber. At the same time, the presence of mucilage, which is a polysaccharide with hydrocolloidal rheological properties, shows promise as a thickening agent suitable for inclusion in many types of food products. During the experimental procedure 4 samples of cladode flour were produced by combining two different drying processes and two different grinding operations. After being cut up into uniform rectangular pieces, cladodes were predried at a temperature of 45o C in a forced air drying oven and then finally dried in a vacuum oven set up either in 45o C or 60o C. The two distinct batches of dehydraded cactus stem produced were then ground to flour in a hammer mill, and half of the produced flour were reprocessed in a jet mill. Finally, after the final preparation of the 4 samples, analysis of the particles' shape and size, their colour values, solubility, WHC and OHC, moisture and dietary fiber content, and finally, the rheological properties and sedimentation rates of 5% w/v dispersions of them in distilled water, were conducted. Flour samples were separated as coarse and fine flours, showing significant changes in median particle size during grinding. Both processes caused intense changes in the color properties of the flours, with the higher final drying temperature resulting in a slightly heat-degraded product. Moisture and water activity were found to be low enough for the samples to be proclaimed stable and safe from microbial, enzymical and oxidative degradation (0.2 < aw < 0.4), while bulk density reduction was observed during final drying at 60°C. Suspensions of all samples exhibited pseudoplastic behavior and dependence of viscosity on temperature, while reprocessing of the flours in the jet mill was found to alter their rheological properties, possibly due to destruction of the mucilage's structure. Dietary fiber content was found to be extremely high for all samples 13 (> 40%), but no safe conclusions can be drawn for the influence of drying and grinding treatments. Solubility and oil retention capacity were mainly affected by grinding, while the water retention capacity was reduced by increasing the final drying temperature of the cladodes. Finally, all flour suspensions were judged to be extremely unstable during the sedimentation test. Based on the results of the present study, it is evident that both heat treatment during drying and grinding of prickly pear tree significantly affect the physical and technological properties of the resulting flour, while further investigations of the milling techniques and their influence are deemed as necessary. At the same time, the extremely high dietary fiber content, combined with its interesting rheological properties, suggest a possible use for the cladode flour as a texture modifier in functional food and nutraceutical products.
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Papers by Manos Bazanis
In the present study, the determination of the appropriate conditions for maximizing the germination of its seeds in both in vitro and in vivo conditions was initially investigated. Two seed lots collected from a native population of the species on Mount Kallidromo, Fthiotida, dry-stored for 0 or 12 months, were used, without any pre-treatment.
Regarding in vitro germination, the seeds were surface sterilized with a 20% commercial bleach water solution for 10 minutes, were then rinsed with distilled water and afterwards were placed in Petri dishes containing ½ MS medium, under 16 h photoperiod from 37.5 μmol m-2 s-1 fluorescent light, at temperatures of 5, 10, 15, 20 or 25 °C. The optimum temperature for seed germination was 15 °C, in which the highest germination ability in both recently collected (98%) and 12-month-old seeds (100 %) was observed. The lowest germination percentages were recorded at the two extreme temperatures of 5 °C and 25 °C, with particularly low values for recently collected seeds (18% and 15%). At all temperatures, minus that of 5 °C, the seeds germinated rapidly (T50 = 2-6 d). The duration of the seeds’ dry storage significantly affected their germination, increasing the germination percentage at the 2 extreme temperatures and demonstrating the positive effect of dry afterripening. As for ex vitro germination, the seeds were placed in pots with a mixture of peat-perlite (1: 1, v/v) and were incubated in growing chambers at temperatures of 15, 20 or 25 °C. The highest germination percentage was observed at 15 °C for both seed lots (97-99%), while the lowest at the temperature of 25 °C (62% and 4% for the 0- and 12-months-old seeds respectively). Germination ability was slightly lower in ex vitro germination, especially at 25 °C.
Furthermore, the micropropagation of the species from explants excised from 2-month-old seedlings was investigated on solid substrates. Substrates containing MS medium and 8 g L-1 agar were used in almost all substages of the proliferation stage, and the effects of cytokinins BA, 2iP and ZEA, with the absence or the presence of auxin NAA, were investigated, using explants derived from non-hyperhydric or hyperhydric shoots. In the initial culture substrates containing 0.1 mg L-1 BA or 0.1 or 0.5 mg L-1 2iP the explants produced shoots at a high percentage (72-87%), but many of these were shown to be hyperhydric, with abnormal morphology and vitreous appearance. The number of hyperhydric shoots and the number of nodes seemed to be higher on substrates containing 2iP, with the largest number of normal shoots (2.3) appearing in the substrate containing 0.1 mg L-1 BA.
During the 1st subculture stage, hyperhydric shoots were observed in bigger numbers in the substrate containing 2iP, while an increase in shoot proliferation and the number of hyperhydric shoots was correlated with the use of hyperhydric explants grown on hormone-free MS substrate. In the 2nd subculture stage, the presence of 0.1 mg L-1 BA yielded the largest number of shoots regardless of the physiology of the explants, while the addition of 0.05 mg L-1 resulted in a significant increase in the number of normal shoots and a reduction in hyperhydricity rates when hyperhydric explants were used. In the 3rd subculture, when explants derived from nonhyperhydric shoots were used the highest value of the multiplication index (4.5) and the maximum number of shoots (3.6) was recorded in MS substrate containing 2 mg L-1 BA. Increasing the concentration of agar to 12 g L-1 produced the largest number of shoots (2.4) when hyperhydric explants were used. In both cases, the highest percentages of hyperhydricity were recorded on MS substrate containing 0.1 mg L-1 ZEA. In contrast, during the 4th subculture, the use of this substrate resulted in the greatest multiplication index value at this stage (4.8).
Overall, the use of MS substrate with 0.1 mg L-1 BA and 0.05 mg L-1 NAA resulted in the highest values of the proliferation index (5.1) regardless of the physiology of the explants used, with its maximum value (5.2) recorded from the culture of hyperhydric explants on MS substrate containing 0.1 mg L-1 BA and 12 g L-1 agar. The presence of phytohormones in the substrates increased the production of callus around the base of the explants, while high concentrations of cytokinins lessened the occurence of roots.
D. cruentus microshoots were rooted in MS or ½ MS substrates in the presence or absence of IBA. The use of MS substrate resulted in lower rooting rates (55-70%) when lower concentrations of IBA were used (0 or 0.1 mg L-1). The optimal concentration of IBA was found to be 0.5 mg L-1 regardless of the multiplication substrate where the microshoots originated or the nutrient medium used in the rooting substrate, with rooting rates of 83-100%, while in some instances a carry over effect, caused by the cytokinin content of the shoot proliferation substrates, was observed on the roots’ number and median length.
The ex vitro acclimatization of the rooted microshoots was completed with a success rate of 91% using a peat:perlite substrate (1:1, v/v). Significant morphological differences were observed between acclimatized plantlets, including differences in stem length and total number of shoots and nodes, which were correlated with the influence of different shoot proliferation and/or rooting substrates, while the presence of IBA during rooting seemed to have an amendable effect on their survival. Finally, the use of an integrated, 60-days-long propagation protocol with shoot proliferation and rooting occurring concurrently in one stage on MS substrates free of PGRs or containing BA or 2iP and NAA produced rooted young plants at a high percentage (88%), which had the maximum observed total number of shoots and nodes and were then successfully acclimatized, surviving at a percentage of 86%.
Scientific area: Horticulture
Keywords: Dianthus cruentus, native ornamental plant, germination ecophysiology, seed germination in vitro, seed germination temperature, seed lot age, dry afterripening, in vitro propagation, solid culture, seedling explant, hyperhydricity, hyperhydric explant, callus induction, in vitro rooting, ex vitro acclimatization, cytokinins, IBA, carry over effect, acclimatized plantlets’ morphology
During the experimental procedure 4 samples of cladode flour were produced by combining two different drying processes and two different grinding operations. After being cut up into uniform rectangular pieces, cladodes were predried at a temperature of 45o C in a forced air drying oven and then finally dried in a vacuum oven set up either in 45o C or 60o C. The two distinct batches of dehydraded cactus stem produced were then ground to flour in a hammer mill, and half of the produced flour were reprocessed in a jet mill. Finally, after the final preparation of the 4 samples, analysis of the particles' shape and size, their colour values, solubility, WHC and OHC, moisture and dietary fiber content, and finally, the rheological properties and sedimentation rates of 5% w/v dispersions of them in distilled water, were conducted.
Flour samples were separated as coarse and fine flours, showing significant changes in median particle size during grinding. Both processes caused intense changes in the color properties of the flours, with the higher final drying temperature resulting in a slightly heat-degraded product. Moisture and water activity were found to be low enough for the samples to be proclaimed stable and safe from microbial, enzymical and oxidative degradation (0.2 < aw < 0.4), while bulk density reduction was observed during final drying at 60°C. Suspensions of all samples exhibited pseudoplastic behavior and dependence of viscosity on temperature, while reprocessing of the flours in the jet mill was found to alter their rheological properties, possibly due to destruction of the mucilage's structure. Dietary fiber content was found to be extremely high for all samples 13 (> 40%), but no safe conclusions can be drawn for the influence of drying and grinding treatments. Solubility and oil retention capacity were mainly affected by grinding, while the water retention capacity was reduced by increasing the final drying temperature of the cladodes. Finally, all flour suspensions were judged to be extremely unstable during the sedimentation test.
Based on the results of the present study, it is evident that both heat treatment during drying and grinding of prickly pear tree significantly affect the physical and technological properties of the resulting flour, while further investigations of the milling techniques and their influence are deemed as necessary. At the same time, the extremely high dietary fiber content, combined with its interesting rheological properties, suggest a possible use for the cladode flour as a texture modifier in functional food and nutraceutical products.
In the present study, the determination of the appropriate conditions for maximizing the germination of its seeds in both in vitro and in vivo conditions was initially investigated. Two seed lots collected from a native population of the species on Mount Kallidromo, Fthiotida, dry-stored for 0 or 12 months, were used, without any pre-treatment.
Regarding in vitro germination, the seeds were surface sterilized with a 20% commercial bleach water solution for 10 minutes, were then rinsed with distilled water and afterwards were placed in Petri dishes containing ½ MS medium, under 16 h photoperiod from 37.5 μmol m-2 s-1 fluorescent light, at temperatures of 5, 10, 15, 20 or 25 °C. The optimum temperature for seed germination was 15 °C, in which the highest germination ability in both recently collected (98%) and 12-month-old seeds (100 %) was observed. The lowest germination percentages were recorded at the two extreme temperatures of 5 °C and 25 °C, with particularly low values for recently collected seeds (18% and 15%). At all temperatures, minus that of 5 °C, the seeds germinated rapidly (T50 = 2-6 d). The duration of the seeds’ dry storage significantly affected their germination, increasing the germination percentage at the 2 extreme temperatures and demonstrating the positive effect of dry afterripening. As for ex vitro germination, the seeds were placed in pots with a mixture of peat-perlite (1: 1, v/v) and were incubated in growing chambers at temperatures of 15, 20 or 25 °C. The highest germination percentage was observed at 15 °C for both seed lots (97-99%), while the lowest at the temperature of 25 °C (62% and 4% for the 0- and 12-months-old seeds respectively). Germination ability was slightly lower in ex vitro germination, especially at 25 °C.
Furthermore, the micropropagation of the species from explants excised from 2-month-old seedlings was investigated on solid substrates. Substrates containing MS medium and 8 g L-1 agar were used in almost all substages of the proliferation stage, and the effects of cytokinins BA, 2iP and ZEA, with the absence or the presence of auxin NAA, were investigated, using explants derived from non-hyperhydric or hyperhydric shoots. In the initial culture substrates containing 0.1 mg L-1 BA or 0.1 or 0.5 mg L-1 2iP the explants produced shoots at a high percentage (72-87%), but many of these were shown to be hyperhydric, with abnormal morphology and vitreous appearance. The number of hyperhydric shoots and the number of nodes seemed to be higher on substrates containing 2iP, with the largest number of normal shoots (2.3) appearing in the substrate containing 0.1 mg L-1 BA.
During the 1st subculture stage, hyperhydric shoots were observed in bigger numbers in the substrate containing 2iP, while an increase in shoot proliferation and the number of hyperhydric shoots was correlated with the use of hyperhydric explants grown on hormone-free MS substrate. In the 2nd subculture stage, the presence of 0.1 mg L-1 BA yielded the largest number of shoots regardless of the physiology of the explants, while the addition of 0.05 mg L-1 resulted in a significant increase in the number of normal shoots and a reduction in hyperhydricity rates when hyperhydric explants were used. In the 3rd subculture, when explants derived from nonhyperhydric shoots were used the highest value of the multiplication index (4.5) and the maximum number of shoots (3.6) was recorded in MS substrate containing 2 mg L-1 BA. Increasing the concentration of agar to 12 g L-1 produced the largest number of shoots (2.4) when hyperhydric explants were used. In both cases, the highest percentages of hyperhydricity were recorded on MS substrate containing 0.1 mg L-1 ZEA. In contrast, during the 4th subculture, the use of this substrate resulted in the greatest multiplication index value at this stage (4.8).
Overall, the use of MS substrate with 0.1 mg L-1 BA and 0.05 mg L-1 NAA resulted in the highest values of the proliferation index (5.1) regardless of the physiology of the explants used, with its maximum value (5.2) recorded from the culture of hyperhydric explants on MS substrate containing 0.1 mg L-1 BA and 12 g L-1 agar. The presence of phytohormones in the substrates increased the production of callus around the base of the explants, while high concentrations of cytokinins lessened the occurence of roots.
D. cruentus microshoots were rooted in MS or ½ MS substrates in the presence or absence of IBA. The use of MS substrate resulted in lower rooting rates (55-70%) when lower concentrations of IBA were used (0 or 0.1 mg L-1). The optimal concentration of IBA was found to be 0.5 mg L-1 regardless of the multiplication substrate where the microshoots originated or the nutrient medium used in the rooting substrate, with rooting rates of 83-100%, while in some instances a carry over effect, caused by the cytokinin content of the shoot proliferation substrates, was observed on the roots’ number and median length.
The ex vitro acclimatization of the rooted microshoots was completed with a success rate of 91% using a peat:perlite substrate (1:1, v/v). Significant morphological differences were observed between acclimatized plantlets, including differences in stem length and total number of shoots and nodes, which were correlated with the influence of different shoot proliferation and/or rooting substrates, while the presence of IBA during rooting seemed to have an amendable effect on their survival. Finally, the use of an integrated, 60-days-long propagation protocol with shoot proliferation and rooting occurring concurrently in one stage on MS substrates free of PGRs or containing BA or 2iP and NAA produced rooted young plants at a high percentage (88%), which had the maximum observed total number of shoots and nodes and were then successfully acclimatized, surviving at a percentage of 86%.
Scientific area: Horticulture
Keywords: Dianthus cruentus, native ornamental plant, germination ecophysiology, seed germination in vitro, seed germination temperature, seed lot age, dry afterripening, in vitro propagation, solid culture, seedling explant, hyperhydricity, hyperhydric explant, callus induction, in vitro rooting, ex vitro acclimatization, cytokinins, IBA, carry over effect, acclimatized plantlets’ morphology
During the experimental procedure 4 samples of cladode flour were produced by combining two different drying processes and two different grinding operations. After being cut up into uniform rectangular pieces, cladodes were predried at a temperature of 45o C in a forced air drying oven and then finally dried in a vacuum oven set up either in 45o C or 60o C. The two distinct batches of dehydraded cactus stem produced were then ground to flour in a hammer mill, and half of the produced flour were reprocessed in a jet mill. Finally, after the final preparation of the 4 samples, analysis of the particles' shape and size, their colour values, solubility, WHC and OHC, moisture and dietary fiber content, and finally, the rheological properties and sedimentation rates of 5% w/v dispersions of them in distilled water, were conducted.
Flour samples were separated as coarse and fine flours, showing significant changes in median particle size during grinding. Both processes caused intense changes in the color properties of the flours, with the higher final drying temperature resulting in a slightly heat-degraded product. Moisture and water activity were found to be low enough for the samples to be proclaimed stable and safe from microbial, enzymical and oxidative degradation (0.2 < aw < 0.4), while bulk density reduction was observed during final drying at 60°C. Suspensions of all samples exhibited pseudoplastic behavior and dependence of viscosity on temperature, while reprocessing of the flours in the jet mill was found to alter their rheological properties, possibly due to destruction of the mucilage's structure. Dietary fiber content was found to be extremely high for all samples 13 (> 40%), but no safe conclusions can be drawn for the influence of drying and grinding treatments. Solubility and oil retention capacity were mainly affected by grinding, while the water retention capacity was reduced by increasing the final drying temperature of the cladodes. Finally, all flour suspensions were judged to be extremely unstable during the sedimentation test.
Based on the results of the present study, it is evident that both heat treatment during drying and grinding of prickly pear tree significantly affect the physical and technological properties of the resulting flour, while further investigations of the milling techniques and their influence are deemed as necessary. At the same time, the extremely high dietary fiber content, combined with its interesting rheological properties, suggest a possible use for the cladode flour as a texture modifier in functional food and nutraceutical products.