Genotypic Differences in Root Morphology and Leaf Photosynthesis of Cotton Seedlings Treated with Phosphorus-deficient Solutions
A laboratory experiment was carried out to study the root morphology and leaf photosynthetic characteristics of three colored cottons (CCRI 51,light brown cotton;CCRI 81,dark brown cotton;and CCRI 82,dark green cotton) and one white cotton under different levels of phosphorus.The results showed that lower level phosphorus treatments significantly increased root length and surface area,while no-phosphorus treatments seriously inhibited root growth.As the duration of the treatment increased,we found that the cotton root had carried out self-regulation and reduced the impact of phosphorus deficiency.Under treatments of lower levels of phosphorus the increased ratio of root length,root surface area,root volume and root/shoot ratio of GX 3 were the highest 10 days after treatment.In CCRI 51,levels were the highest 20 days after treatment.Under no-phosphorus treatments,the inhibition rates ofGX 3 and CCRI 81 root morphology 20 days after treatment were higher than 10 days after treatment.Levels in the other varieties improved as the period of stress continued.The ranking of the different varieties with respect to light saturation point,maximum photosynthetic rate and light compensation point of leaves was CCRI 51 ＞ GX 3 ＞ CCRI 81 ＞ CCRI 82.As the supply of phosphorus decreased,light saturation point and the maximum photosynthetic rate of GX 3 were gradually reduced,but light saturation point of CCRI 51 and CCRI 81 were shown as lower phosphorus ＞ no phosphorus ＞ suitable phosphorus.Under these experimental conditions,we found that white cotton had a short-term ability to compensate for phosphorus stress;light-brown cotton and dark-green cotton had a long-term ability to compensate for phosphorus stress;and dark-brown cotton was less sensitive to phosphorus phosphate stress.
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