Winter wheat (Trificum aesfivum L. cv Monopol), spring wheat (Trificum aesfivum L. cv Katepwa), and winter rye (Secale cereale 1. cv Musketeer) grown at 5°C and moderate irradiance (250 pmol m-2 -1 s ) (5/250) exhibit an increased... more
Winter wheat (Trificum aesfivum L. cv Monopol), spring wheat (Trificum aesfivum L. cv Katepwa), and winter rye (Secale cereale 1. cv Musketeer) grown at 5°C and moderate irradiance (250 pmol m-2 -1 s ) (5/250) exhibit an increased tolerance to photoinhibition at low temperature in comparison to plants grown at 20°C and 250 pmol m-'s-' (20/250). However, 5/250 plants exhibited
The role of growth temperature and growth irradiance on the regulation of the stoichiometry and function of the photosynthetic apparatus was examined in the cyanobacterium Plectonema boryanum UTEX 485 by comparing mid-log phase cultures... more
The role of growth temperature and growth irradiance on the regulation of the stoichiometry and function of the photosynthetic apparatus was examined in the cyanobacterium Plectonema boryanum UTEX 485 by comparing mid-log phase cultures grown at either 29°C/150 micromol m-2 s-1, 29°C/750 micromol m-2 s-1, 15°C/150 micromol m-2 s-1, or 15°C/10 micromol m-2 s-1. Cultures grown at 29°C/750 micromol m-2 s-1 were structurally and functionally similar to those grown at 15°C/150 micromol m-2 s-1, whereas cultures grown at 29°C/150 micromol m-2 s-1 were structurally and functionally similar to those grown at 15°C/10 micromol m-2 s-1. The stoichiometry of specific components of the photosynthetic apparatus, such as the ratio of photosystem (PS) I to PSII, phycobilisome size and the relative abundance of the cytochrome b6/f complex, the plastoquinone pool size, and the NAD(P)H dehydrogenase complex were regulated by both growth temperature and growth irradiance in a similar manner. This indicates that temperature and irradiance may share a common sensing/signaling pathway to regulate the stoichiometry and function of the photosynthetic apparatus in P. boryanum. In contrast, the accumulation of neither the D1 polypeptide of PSII, the large subunit of Rubisco, nor the CF1 a-subunit appeared to be regulated by the same mechanism. Measurements of P700 photooxidation in vivo in the presence and absence of inhibitors of photosynthetic electron transport coupled with immunoblots of the NAD(P)H dehydrogenase complex in cells grown at either 29°C/750 micromol m-2 s-1 or 15°C/150 micromol m-2 s-1 are consistent with an increased flow of respiratory electrons into the photosynthetic intersystem electron transport chain maintaining P700 in a reduced state relative to cells grown at either 29°C/150 micromol m-2 s-1 or 15°C/10 micromol m-2 s-1. These results are discussed in terms of acclimation to excitation pressure imposed by either low growth temperature or high growth irradiance.
Winter wheat (Triticum aestivum L. cv Monopol), spring wheat (Triticum aestivum L. cv Katepwa), and winter rye (Secale cereale L. cv Musketeer) grown at 5[deg]C and moderate irradiance (250 [mu]mol m-2 s-1) (5/250) exhibit an increased... more
Winter wheat (Triticum aestivum L. cv Monopol), spring wheat (Triticum aestivum L. cv Katepwa), and winter rye (Secale cereale L. cv Musketeer) grown at 5[deg]C and moderate irradiance (250 [mu]mol m-2 s-1) (5/250) exhibit an increased tolerance to photoinhibition at low temperature in comparison to plants grown at 20[deg]C and 250 [mu]mol m-2 s-1 (20/250). However, 5/250 plants exhibited a higher photosystem II (PSII) excitation pressure (0.32-0.63) than 20/250 plants (0.18-0.21), measured as 1 - qP, the coefficient of photochemical quenching. Plants grown at 20[deg]C and a high irradiance (800 [mu]mol m-2 s-1) (20/800) also exhibited a high PSII excitation pressure (0.32-0.48). Similarly, plants grown at 20/800 exhibited a comparable tolerance to photoinhibition relative to plants grown at 5/250. In contrast to a recent report for Chlorella vulgaris (D.P. Maxwell, S. Falk, N.P.A. Huner [1995] Plant Physiol 107: 687-694), this tolerance to photoinhibition occurs in winter rye with ...
Winter wheat (Triticum aestivum L. cv Monopol), spring wheat (Triticum aestivum L. cv Katepwa), and winter rye (Secale cereale L. cv Musketeer) grown at 5[deg]C and moderate irradiance (250 [mu]mol m-2 s-1) (5/250) exhibit an increased... more
Winter wheat (Triticum aestivum L. cv Monopol), spring wheat (Triticum aestivum L. cv Katepwa), and winter rye (Secale cereale L. cv Musketeer) grown at 5[deg]C and moderate irradiance (250 [mu]mol m-2 s-1) (5/250) exhibit an increased tolerance to photoinhibition at low temperature in comparison to plants grown at 20[deg]C and 250 [mu]mol m-2 s-1 (20/250). However, 5/250 plants exhibited a higher photosystem II (PSII) excitation pressure (0.32-0.63) than 20/250 plants (0.18-0.21), measured as 1 - qP, the coefficient of photochemical quenching. Plants grown at 20[deg]C and a high irradiance (800 [mu]mol m-2 s-1) (20/800) also exhibited a high PSII excitation pressure (0.32-0.48). Similarly, plants grown at 20/800 exhibited a comparable tolerance to photoinhibition relative to plants grown at 5/250. In contrast to a recent report for Chlorella vulgaris (D.P. Maxwell, S. Falk, N.P.A. Huner [1995] Plant Physiol 107: 687-694), this tolerance to photoinhibition occurs in winter rye with ...
The basis of the increased resistance to photoinhibition upon growth at low temperature was investigated. Photosystem II (PSII) excitation pressure was estimated in vivo as 1 - qp (photochemical quenching). We established that Chlorella... more
The basis of the increased resistance to photoinhibition upon growth at low temperature was investigated. Photosystem II (PSII) excitation pressure was estimated in vivo as 1 - qp (photochemical quenching). We established that Chlorella vulgaris exposed to ei- ther 5'C/150 pmol m-'s-l or 27°C/2200 pmol m-'s-l experi- enced a high PSll excitation pressure of 0.70 to 0.75. In contrast, Chlorella exposed to either 27"C/150 pmol m-, s-l or 5'C/20 pmol m-'s-l experienced a low PSll excitation pressure of 0.10 to 0.20. Chlorella grown under either regime at high PSll excitation pressure exhibited: (a) 3-fold higher light-saturated rates of O, evolution; (b) the complete conversion of PSlh centers to PSllp centers; (c) a 3-fold lower epoxidation state of the xanthophyll cycle intermediates; (d) a 2.4-fold higher ratio of chlorophyll Jb; and (e) a lower abundance of light-harvesting polypeptides than Chlorella grown at either regime at low PSll excitation press...
Winter wheat (Trificum aesfivum L. cv Monopol), spring wheat (Trificum aesfivum L. cv Katepwa), and winter rye (Secale cereale 1. cv Musketeer) grown at 5°C and moderate irradiance (250 micromol m-2 s -1 ) (5/250) exhibit an increased... more
Winter wheat (Trificum aesfivum L. cv Monopol), spring wheat (Trificum aesfivum L. cv Katepwa), and winter rye (Secale cereale 1. cv Musketeer) grown at 5°C and moderate irradiance (250 micromol m-2 s -1 ) (5/250) exhibit an increased tolerance to photoinhibition at low temperature in comparison to plants grown at 20°C and 250 micrpmol m-2s-1 (20/250). However, 5/250 plants exhibited a higher photosystem II (PSII) excitation pressure (0.32-0.63) than 20/250 plants (0.18-0.21), measured as 1 - qp, the coefficient of photochemical quenching. Plants grown at 20°C and a high irradiance (800 micromol m-2s-1) (20/800) also exhibited a high PSll excitation pressure (0.32-0.48). Similarly, plants grown at 20/800 exhibited a comparable tolerance to photoinhibition relative to plants grown at 5/250. In contrast to a recent report for Chlorella vulgaris (D.P. Maxwell, S. Falk, N.P.A. Huner [1995] Plant Physiol 107: 687-694), this tolerance to photoinhibition occurs in winter rye with minimal adjustment to polypeptides of the PSll light-harvesting complex, chlorophyll a/b ratios, or xanthophyll cycle carotenoids. However, Monopol winter wheat exhibited a 2.5-fold stimulation of sucrosephosphate synthase activity upon growth at 5/250, in comparison to Katepwa spring wheat. We demonstrate that low-temperatureinduced tolerance to photoinhibition is not a low-temperaturegrowth effect per se but, instead, reflects increased photosynthetic capacity in response to elevated PSll excitation pressure, which may be modulated by either temperature or irradiance.
