ISHS Acta Horticulturae 748: II International Symposium on Acclimatization and Establishment of Micropropagated Plants
LIGHT-DEPENDENT PHOTOSYNTHETIC CHARACTERISTICS INDICATED BY CHLOROPHYLL FLUORESCENCE IN MICROPROPAGATED PLANTS OF RHODODENDRON PONTICUM SUBSP. BAETICUM DURING ACCLIMATION |
| Authors: | M.L. Osório, J. Osório, A. Romano |
| Keywords: | electron transport, light-acclimation, photoinhibition, photochemistry, thermal energy dissipation |
| Abstract:
Micropropagated plants of Rhododendron ponticum subsp. baeticum after acclimatization were grown in natural conditions at three levels of irradiance (HL = 1000, IL = 300 and LL = 80 µmol m-2 s-1) using permanent shading. Light acclimation of photosynthesis was characterized using chlorophyll a fluorescence of intact leaves. There was a clear association between light acclimation of photosynthetic performance and growth irradiance. In general, the saturated electron transport rate, ETR, was higher for high (HL) and intermediate light (IL) than for low-light (LL) grown plants. The response of qp, which represents PSII openness to incident light, indicates a ranking of tolerant capacity to photoinhibition of HL>IL>LL. The light acclimation of the non-radiative dissipation of excess energy in the antenna, qN, was not very clear despite the highest value shown by HL plants. A clear feature of the light response of qp and qN is the gradual replacement of qp by qN with increasing light. However, this photoprotective strategy in LL plants seems to be less efficient than in HL plants. Moreover, after an exposition to strong light environment, the maximal photochemical efficiency of PSII (Fv/Fm) did not recover after 24 hours in IL and LL plants. This great plasticity of photosynthesis in R. ponticum plants indicates that the high light regimes during acclimation in the field can beneficiate the plant growth without photoinhibition effects. | |
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