Chin J Plan Ecolo ›› 2008, Vol. 32 ›› Issue (3): 681-689.DOI: 10.3773/j.issn.1005-264x.2008.03.018

• Research Articles • Previous Articles     Next Articles

EFFECTS OF WATER DEFICIT ON PHOTOCHEMICAL ACTIVITY AND EXCITATION ENERGY DISSIPATION OF PHOTOSYNTHETIC APPARATUS IN COTTON LEAVES DURING FLOWERING AND BOLL-SETTING STAGES

HANG Ya-Li1; LUO Hong-Hai1; ZHANG Wang-Feng1*; FAN Da-Yong2; HE Za-Ju1; BAI Hui-Dong1   

  1. 1Key Laboratory of Oasis Ecology Agriculture of Xinjiang Construction Crops, College of Agriculture, Shihezi University, Shihezi, Xinjiang 832003, China; 2 State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
  • Online:2008-05-30 Published:2008-05-30
  • Contact: ZHANG Wang-Feng

Abstract: Aims Cotton (Gossypium hirsutum) is a major crop in Xinjiang Province , Northwest China. Because Xinjiang is characterized
by deficiency of water resource and strong irradiance, study of water deficit on photoinhibition of cotton in this area is
crucial not only for efficient irrigation, but also for physiological exploration of plant photo-protection strategy.
Methods We investigated the effects of water deficit on physiological characteristics of cotton in the field. We measured
diurnal variations of photon flux density (PFD), leaf temperature (Tleaf), pre-dawn maximal photochemical efficiency of PSⅡ
(Fv/Fm), PSⅡphotochemical efficiency (φPSⅡ), electron transport rate (ETR), photochemical quenching (qp) and non-
photochemical quenching (NPQ ), as well as chlorophyll content and water potential of cotton leaves subjected to different
water supplies.
Important findings Compared to control (70%-75% of field capacity), the diurnal variation of leaf incident PFD was similar
and Tleaf was higher with mild water deficit (55%-60% of field capacity). The diurnal variation of leaf incident PFD with
moderate water deficit (40%-45% of field capacity) was similar before 12∶00 and then lower, as a result of leaf wilting than
in the control. Leaf temperature with moderate water deficit was significantly higher than in the control during daytime. No
significant effects were observed on pre-dawn Fv/Fm; all values were between 0.83 and 0.84. There were no differences in
diurnal variations of φPSⅡ, ETR and qp between mild water deficit and control. However, NPQ with mild water deficit was
similar before noon and then lower than the control. At 12∶00, φPSⅡ, ETR and qp with moderate water deficit were
significantly decreased and then recovered gradually to control values, possibly due to the decreased leaf incident PFD
resulting from temporary and passive leaf wilting. However, NPQ with moderate water deficit was higher before 12∶00 and
similar at 14∶00 but after that was lower than control. Water potential and chlorophyll content decreased with water
deficits, but the Chl a/b ratio increased. All results showed that cotton leaves could acclimate to water deficit through
changing leaf orientation and chlorophyll content to regulate light energy captured by leaves and changing electron transport
rate and thermal dissipation ratio. We suggest that the risk of photosynthetic apparatus damage by excessive excitation
energy could be decreased greatly through passive movement of cotton leaf wilting with moderate water deficit.