Physical dormancy (PY) occurs in all three subfamilies of Fabaceae namely Mimosoideae, Papilionoi... more Physical dormancy (PY) occurs in all three subfamilies of Fabaceae namely Mimosoideae, Papilionoideae and Caesalpinioideae making it one of the largest plant family in terms of number of species with PY. However, only little is known about water gap structure and germination ecology of species in Caesalpinioideae. Freshly collected seeds of Delonix regia (Caesalpinioideae) did not imbibe water, thus they had PY. Both dry heat and wet heat were effective in breaking dormancy, however longer duration was required at low temperatures (80 °C) and shorter duration at 90 °C. Seeds buried in field for two years germinated to 21 and 42% after first and second summer respectively compared with 3% germination in seeds at the time of maturity. Seeds incubated at 15/60 °C in laboratory (mimicking the summer conditions) for three months supported this conclusion, as dormancy was relieved in 18 and 24% of seeds stored dry and watered intermediately respectively. All the dormancy breaking treatmen...
Dry seeds of Lactuca sativa (iceberg lettuce) and L. sativa cv. Hance salad that had imbibed wate... more Dry seeds of Lactuca sativa (iceberg lettuce) and L. sativa cv. Hance salad that had imbibed water for 40 hours at 4°C (to moisture contents of 68 ± 3.9 and 62 ± 2.9%, respectively) followed by imbibition in 15 or 35% dimethyl sulfoxide (DMSO) for eight hours, were cooled to various sub-zero temperatures (>-40°C) at 3 or 60°C hour-1 in a programmable freezer. After cooling to the various low temperatures, seeds were either thawed directly in a water bath at 40°C or plunged into liquid nitrogen for one week before thawing at 40°C. Viability was assessed as the number of seeds that germinated at 21°C. The ice formation temperature, which was detected using a thermocouple during cooling (in the range of -12 to -40°C), did not affect subsequent germination following liquid nitrogen storage. The higher concentration of DMSO was toxic whilst the lower concentration was essential for higher seed survival after both sub-zero and liquid nitrogen storage. Survival of both cultivars was bes...
Climate change directly affects arctic-alpine plants and acute responses to increased temperature... more Climate change directly affects arctic-alpine plants and acute responses to increased temperatures may be seen in their reproductive fitness and germination ability. However, uncertainties prevail in predicting whether a future warmer climate favors or hampers seed germination in high latitude and high altitude soils and seed germination research in such systems has not been able to provide generalizable patterns of response. The available literature on this subject has been conducted at various locations contributing to difficulties in predicting the response of arctic-alpine seeds to climate change. Here, we show that discrepancies in seed collection, dormancy breaking treatments, and germination conditions found in the published literature are possible reasons for our inability to draw large scale conclusions. We explore how these factors influence the results and highlight the fact that many of the previous investigations have reported the effects of warmer temperature, rather than a warmer climate and all the associated complex environmental interactions, on seed germination. We recommend that long-term monitoring of seed response to treatments that mimic the present and future alpine climate is likely to produce more ecologically meaningful insights and suggest several practical steps that researchers can take that would facilitate greater coherence between studies.
Physical dormancy (PY) occurs in all three subfamilies of Fabaceae namely Mimosoideae, Papilionoi... more Physical dormancy (PY) occurs in all three subfamilies of Fabaceae namely Mimosoideae, Papilionoideae and Caesalpinioideae making it one of the largest plant family in terms of number of species with PY. However, only little is known about water gap structure and germination ecology of species in Caesalpinioideae. Freshly collected seeds of Delonix regia (Caesalpinioideae) did not imbibe water, thus they had PY. Both dry heat and wet heat were effective in breaking dormancy, however longer duration was required at low temperatures (80 °C) and shorter duration at 90 °C. Seeds buried in field for two years germinated to 21 and 42% after first and second summer respectively compared with 3% germination in seeds at the time of maturity. Seeds incubated at 15/60 °C in laboratory (mimicking the summer conditions) for three months supported this conclusion, as dormancy was relieved in 18 and 24% of seeds stored dry and watered intermediately respectively. All the dormancy breaking treatmen...
Dry seeds of Lactuca sativa (iceberg lettuce) and L. sativa cv. Hance salad that had imbibed wate... more Dry seeds of Lactuca sativa (iceberg lettuce) and L. sativa cv. Hance salad that had imbibed water for 40 hours at 4°C (to moisture contents of 68 ± 3.9 and 62 ± 2.9%, respectively) followed by imbibition in 15 or 35% dimethyl sulfoxide (DMSO) for eight hours, were cooled to various sub-zero temperatures (>-40°C) at 3 or 60°C hour-1 in a programmable freezer. After cooling to the various low temperatures, seeds were either thawed directly in a water bath at 40°C or plunged into liquid nitrogen for one week before thawing at 40°C. Viability was assessed as the number of seeds that germinated at 21°C. The ice formation temperature, which was detected using a thermocouple during cooling (in the range of -12 to -40°C), did not affect subsequent germination following liquid nitrogen storage. The higher concentration of DMSO was toxic whilst the lower concentration was essential for higher seed survival after both sub-zero and liquid nitrogen storage. Survival of both cultivars was bes...
Climate change directly affects arctic-alpine plants and acute responses to increased temperature... more Climate change directly affects arctic-alpine plants and acute responses to increased temperatures may be seen in their reproductive fitness and germination ability. However, uncertainties prevail in predicting whether a future warmer climate favors or hampers seed germination in high latitude and high altitude soils and seed germination research in such systems has not been able to provide generalizable patterns of response. The available literature on this subject has been conducted at various locations contributing to difficulties in predicting the response of arctic-alpine seeds to climate change. Here, we show that discrepancies in seed collection, dormancy breaking treatments, and germination conditions found in the published literature are possible reasons for our inability to draw large scale conclusions. We explore how these factors influence the results and highlight the fact that many of the previous investigations have reported the effects of warmer temperature, rather than a warmer climate and all the associated complex environmental interactions, on seed germination. We recommend that long-term monitoring of seed response to treatments that mimic the present and future alpine climate is likely to produce more ecologically meaningful insights and suggest several practical steps that researchers can take that would facilitate greater coherence between studies.
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