Some light-demanding plants fold their leaves when exposed to high light, such as Bauhinia tenuiflora, some plants do not. Light is the driving force for photosynthesis.
Since high light could induce selective photodamage to photosystem II (PSII), Dr. HUANG Wei and his supervisor Prof. CAO Kunfang of Xishuangbanna Tropical Botanical Garden (XTBG) suggested that the leaves fold themselves to diminish the absorption of light energy and remedy the deficiency of physiological photoprotection for PSII.
A plant that folds its leaves under high light Bauhinia tenuiflora and a plant that does not fold its leaves when exposed to high light Microcos paniculata were chosen for the study.
To test the hypothesis, the researchers determined light responses of non-photochemical quenching (NPQ) and cyclic electron flow (CEF) and the effect of high light on PSII activity in Microcos paniculata and Bauhinia tenuiflora.
Their study found that PSII was much more sensitive to high light stress in the foldable species B. tenuiflora than in the un-foldable species M. paniculata. Furthermore, B. tenuiflora showed much lower capacity of NPQ than M. paniculata .
Their results indicated that under high light, the foldable leaves of B. tenuiflora have lower CEF and NPQ capacity than un-foldable leaves of M. paniculata. Furthermore, PSII is more sensitive to high light in B. tenuiflora than M. paniculata. Those results provide evidence for leaf fold to remedy the deficiency of physiological photoprotection for PS II.
The climatic data in the study was provided by Xishuangbanna Station for Tropical Rain Forest Ecosystem Studies (XSTRE). The study was supported by the National Natural Science Foundation of China (grant 30900174 and 30770226) and the Key Laboratory of National Forestry Bureau for Fast-growing Tree Breeding and Cultivation in Central South China (an open project grant).
The study entitled “Evidence for leaf fold to remedy the deficiency of physiological photoprotection for photosystem II” has been published in Photosynthesis Research, 110 (3): 185-191, DOI 10.1007/s11120-011-9717-2