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RELATIONS BETWEEN SUNFLECK SEQUENCES AND PHOTOINHIBITION OF PHOTOSYNTHESIS IN A TROPICAL RAIN FOREST UNDERSTORY HERB
Author(s) -
Gouallec J. L. Le,
Cornic G.,
Blanc P.
Publication year - 1990
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1990.tb13595.x
Subject(s) - photoinhibition , photosynthesis , biology , understory , botany , quantum yield , photosystem ii , horticulture , zoology , fluorescence , canopy , physics , quantum mechanics
We report the photosynthetic characteristics of a C 3 shade plant native to the tropical rain forest understory. It was shown that Elatostema repens Lour. (Hall) f. ( Urticaceae ) presents a large light adjustment capacity. The effects of several lightfleck sequences on photoinhibition of photosynthesis and carbon gain are analyzed. Photoinhibition is measured both as a decrease in leaf net CO 2 uptake in limiting light (shown to be linearly correlated to quantum yield of O 2 evolution measured at saturating CO 2 ) and as a decrease of the ratio of variable fluorescence (Fv) to maximum fluorescence (Fmax) measured in liquid nitrogen. It is shown that lightflecks (from 10 to 30 min in duration) of 700 μ mol m –2 s –1 (high light) induce photoinhibition, and that the effects of those successive high light periods are additive; there is apparently no recovery from photoinhibition during the low light periods (from 10 to 45 min in duration). In contrast, the Fv/Fmax ratio, though decreasing similarly to quantum yield of net CO 2 uptake on leaves submitted to a continuous illumination of 700 μ mol m –2 s –1 , is only decreased a little on leaves submitted to lightfleck sequences of the same photon flux density. Lightflecks of 250 μ mol m –2 s –1 are not photoinhibitory. Compared to the control maintained under light growth condition (40 μ mol m –2 s –1 ) carbon gain is increased on leaves submitted to lightflecks; this gain remains high throughout the light cycles on leaves submitted to nonphotoinhibitory lightflecks and to the photoinhibitory lightflecks followed by the shortest low light period. In the other cases, carbon gain, higher than that of the control at the beginning of the treatments, decreases and becomes lower than the control carbon gain. Finally, the relevance of photoinhibition in the tropical rain forest understory environment is discussed.