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Revista chilena de historia natural

Print version ISSN 0716-078X


GONZALEZ, JAVIERA; PASTENES, CLAUDIO  and  HORTON, PETER. Effect of temperature, water and light stress on PSII heterogeneity in four bean varieties (Phaseolus vulgaris L.). Rev. chil. hist. nat. [online]. 2001, vol.74, n.4, pp.779-791. ISSN 0716-078X.

Higher plants have developed multiple mechanisms of photoprotection in order to efficiently use the absorbed energy, as well as protecting the photosynthetic apparatus against oxidative damage. Particularly, under environmental conditions, restrictive for the photochemical use of the absorbed energy, such as high light, water stress and high temperatures. PSII complexes are able to change their location and structure as in PSIIß and state transitions, but not exclusively upon light intensity. In the present study, the effect of different environmental stresses on PSII heterogeneity in four bean cultivar (Phaseolus vulgaris L.): Arroz Tuscola (AT), Orfeo INIA (OI), Bayos Titán (BT) and Hallado Dorado (HD), has been assessed. In chamber grown plants, the proportion of the PSIIb centers increases up to a 100 % as the temperature rises. A stronger response was observed, upon water stress. Under field conditions, light stress induced by fixing leaves to horizontal position, further increased the water stress dependent effect on PSIIb centers, from 27 % in free leaves from watered plants up to a 63 % in horizontal leaves from water stressed plants. As for state transitions, an increase was observed in 20 ºC grown plants when exposed to 15 ºC. Also, temperatures from 25 to 35 ºC induced increases in state transitions. Such increases were lowered by water stress, in cultivars AT and OI, maintained in HD and further increased in BT. Even though differences were observed in the extent of the changes on PSIIß and state transitions among varieties, a clear trend to modify the PSII structure in order to decrease its excitation pressure under the stress conditions studied were observed

Keywords : PSIIß; state transitions; Phaseolus vulgaris; chlorophyll fluorescence; photosynthesis; water stress; temperature.

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