水培磷胁迫下不同基因型棉花苗期根系形态及叶片光合特性的差异

水培条件下,以彩棉品种中棉所51号(浅棕)、中棉所81号(深棕)、中棉所82号(深绿)和普通白棉品种国欣棉3号为材料,研究3个不同的磷素(KH2P2O5)水平:缺磷(0 mmol·L-1)、低磷(0.5 mmol·L-1)和适磷(1mmol·L-1)对棉花苗期根系形态、根冠比、叶片光合特性的影响。结果表明:低磷极显著提高了棉花总根长和根表面积;缺磷严重抑制了棉花根系的生长,但是随着处理时间的延长,棉花根系生长得以自我调节,减轻了胁迫的影响。低磷处理后10 d,总根长、根表面积、根体积、根冠比均以白棉提高的最多;处理后20 d则以浅棕棉提高的最多。缺磷胁迫下,白棉和深棕棉在处理后20 d根系生长受到的抑制程度相比于处理后10 d加重,而其他品种则随着胁迫时间的延长,抑制程度减轻。不同品种的光饱和点和最大光合速率差异的表现均是浅棕棉白棉深棕棉深绿棉。随着磷素供应水平的降低,白棉的光饱和点和最大光合速率也逐渐降低,而两个棕色棉的光饱和点则表现为低磷缺磷适磷。表明白棉能耐短期的磷素胁迫,浅棕棉和深绿棉能耐较长期的磷素胁迫,深棕棉对磷素胁迫较钝感。

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 of GX 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.