Abstract
This study investigated sucrose metabolism of the youngest fully expanded main-stem leaf (MSL) and the subtending leaf of cotton (Gossypium hirsutum L.) boll (LSCB) of salt-tolerant (CCRI-79) and salt-sensitive (Simian 3) cultivars and its relationship to boll weight under low, medium and high soil salinity stress in Dafeng, China, in 2013 and 2014. The results showed that with increased soil salinity, 1) both the chlorophyll content and net photosynthetic rate (Pn) decreased, while the internal CO2 concentration firstly declined, and then increased in the MSL and LSCB; 2) carbohydrate contents in the MSL reduced significantly, while sucrose and starch contents in the LSCB increased, as did the activities of sucrose phosphate synthase (SPS) and sucrose synthase (SuSy) in both the MSL and LSCB; 3) but invertase activity in both the MSL and LSCB did not change significantly. Our study also showed that the LSCB was more sensitive to soil salinity than was the MSL. Of the measured physiological indices, higher SPS activity, mainly controlled by sps3, may contribute to adaption of the LSCB to soil salinity stress because SPS is beneficial for efficiently sucrose synthesis, reduction of cellular osmotic potential and combined actions of Pn, and sucrose transformation rate and SPS may contribute to the reduction in boll weight under soil salinity stress.
Highlights
Soil salinity is a major factor limiting agricultural productivity of nearly 20% of the cultivated area and half of the irrigated area worldwide [1, 2]
Chl a, Chl b and Chl(a+b) decreased by 3%–26%, 4%– 18%, and 1%–25% for both cultivars, respectively, indicating that Chl a was the most sensitive index in the the subtending leaf of cotton boll (LSCB) to soil salinity stress, and carotenoids content decreased by 6%–32%, greater than the decreases in Chl a, Chl b and Chl(a+b)
The response of photosynthate formation to soil salinity stress was consistent between the main-stem leaf (MSL) and LSCB
Summary
Soil salinity is a major factor limiting agricultural productivity of nearly 20% of the cultivated area and half of the irrigated area worldwide [1, 2]. Cotton (Gossypium hirsutum L.) is a salttolerant crop that can improve productivity on saline soil and lead to economic development in regions of high salinity. Most studies on halophytes have focused on their morphology, photosynthesis, antioxidant protection system and the ion contents in the soil and in cotton plants [3,4,5]. Soil salinity stress inhibits plant growth, mainly by inhibiting leaf expansion and reducing net photosynthetic rate (Pn) [6]. The decreased Pn is mainly due to PLOS ONE | DOI:10.1371/journal.pone.0156241. The decreased Pn is mainly due to PLOS ONE | DOI:10.1371/journal.pone.0156241 May 26, 2016
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