Leaf Wilting Movement Can Protect Water-Stressed Cotton (<Emphasis Type="Italic">Gossypium hirsutum</Emphasis> L.) Plants Against Photoinhibition of Photosynthesis and Maintain Carbon Assimilation in the Field |
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Authors: | Ya-Li Zhang Hong-Zhi Zhang Ming-Wei Du Wei Li Hong-Hai Luo Wah-Soon Chow Wang-Feng Zhang |
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Institution: | (1) The Key Laboratory of Oasis Eco-agriculture, Xinjiang Production and Construction Group, Shihezi University, Shihezi, 832003, People’s Republic of China;(2) Division of Plant Sciences, Research School of Biology, College of Medicine, Biology and Environment, Australian National University, Canberra, ACT, 0200, Australia; |
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Abstract: | Under severe water stress, leaf wilting is quite general in higher plants. This passive movement can reduce the energy load
on a leaf. This paper reports an experimental test of the hypothesis that leaf wilting movement has a protective function
that mitigates against photoinhibition of photosynthesis in the field. The experiments exposed cotton (Gossypium hirsutum L.) to two water regimes: water-stressed and well-watered. Leaf wilting movement occurred in water-stressed plants as the
water potential decreased to −4.1 MPa, reducing light interception but maintaining comparable quantum yields of photosystem
II (PS II; Yield for short) and the proportion of total PS II centers that were open (qP). Predrawn F
v/F
m (potential quantum yield of PS II) as an indicator of overnight recovery of PS II from photoinhibition was higher than or
similar to that in well-watered plants. Compared with water-stressed cotton leaves for which wilting movement was permitted,
water-stressed cotton leaves restrained from such movement had significantly increased leaf temperature and instantaneous
CO2 assimilation rates in the short term, but reduced Yield, qP, and F
v/F
m. In the long term, predrawn F
v/F
m and CO2 assimilation capacity were reduced in water-stressed leaves restrained from wilting movement. These results suggest that,
under water stress, leaf wilting movement could reduce the incident light on leaves and their heat load, alleviate damage
to the photosynthetic apparatus due to photoinhibition, and maintain considerable carbon assimilation capacity in the long
term despite a partial loss of instantaneous carbon assimilation in the short term. |
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Keywords: | |
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