部分根区灌溉与合理密植对旱区棉花产量和水分生产率的影响

Effects of partial root-zone irrigation and rational close planting on yield and water productivity of cotton in arid area

为揭示部分根区灌溉与合理密植在棉花产量和水分生产率上的互作效应及其生理学机制,探索旱区节水灌溉植棉的新途径,在内蒙古自治区西部大田条件下,采用两因子试验设计研究了灌溉方式(常规灌溉、亏缺灌溉、部分根区灌溉)和种植密度(13.5万、18.0万、22.5万株·hm-2)对棉花生长发育、产量、水分生产率和相关生理指标的影响.结果表明:灌溉方式和种植密度及其互作对棉花生物产量、籽棉产量、产量结构和收获指数有显著影响.常规灌溉条件下,提高密度能显著提高生物产量和单位面积铃数,但铃重和收获指数显著降低,高密度与中等密度下的经济产量相当,并显著高于低密度处理;部分根区灌溉可显著提高棉花叶片中脱落酸(ABA)含量,并显著降低吲哚乙酸(IAA)含量,促进同化物向生殖器官的分配,提高收获指数.随着种植密度的提高,部分根区灌溉下单位面积铃数增加、铃重基本不变,高密度较中、低密度籽棉分别增产6.7%和11.5%.高密度下,部分根区灌溉与常规灌溉的籽棉产量相当,霜前花率提高22.5%,节水30%,水分生产率提高49.3%.种植密度对主茎功能叶光合速率没有显著影响,灌溉方式对光合速率有显著影响,亏缺灌溉显著降低了主茎功能叶的光合速率,而部分根区灌溉的叶片光合速率与常规灌溉相当.部分根区灌溉灌水侧根系茉莉酸(JA)含量和水通道蛋白基因(PIP)表达量显著高于常规灌溉,表明部分根区灌溉下,JA作为信号分子参与了灌水侧根系水分吸收的调控,PIP基因上调表达,根系吸水能力增强,保障了地上部叶片的水分平衡,进而维持了较高的光合速率.部分根区灌溉配合适当密植(22.5万株·hm-2)是旱区节水植棉的重要技术途径.

The objective of this study was to evaluate the effects and underlying physiological mecha-nisms of partial root zone irrigation(PRI)and rational close planting,as well as their interaction on yield and water productivity(WP)of cotton and to explore new alternatives of water-saving irrigation in dry land areas.A factorial field experiment with irrigation mode(normal irrigation,partial root-zone irrigation and deficient irrigation)and plant population density(135000,180000 and 225000 plants·hm-2)was conducted in the west of Inner Mongolia to examine their effects on cotton growth,yield,water productivity and related physiological characters.The results showed that the irrigation mode and plant density as well as their interaction significantly affected the biomass,yield,yield components and harvest index.Under normal irrigation,the biomass and the number of bolls per unit area increased with the increasing of plant density,but the harvest index and boll weight significantly reduced.The yield of high plant density was comparable to that of medium plant density,both of which were increased significantly compared with that of low plant density.The content of abscisic acid(ABA)significantly increased and that of auxin(IAA)significantly reduced in cotton leaves under partial root-zone irrigation,which significantly increased the harvest index by improving the partitioning of assimilates to reproductive organs under partial root-zone irrigation.The number of bolls per unit area increased and boll mass remained unchanged with the increasing of density under partial root-zone irrigation.The yield of high density increased by 6.7%and 11.5%compared with that of medium and low density under partial root zone irrigation.The pre-frost seed cotton increased by 22.5%,the amount of irrigation reduced by 30%,and water productivity increased by 49.3%under partial root zone irrigation compared with that under normal irrigation at high plant density.Plant density did not affect photosynthetic rate(Pn)of functional leaves,but irrigation mode significantly affected Pn.Deficient irrigation significantly reduced the Pn of the main-stem functional leaves,but the Pn under partial root-zone irrigation was comparable to that of normal irrigation.The jasmonate(JA)content and the expression level of plasma membrane intrinsic protein(PIP)gene were significantly increased in the hydrated root under partial root-zone irrigation compared with those under normal irrigation.The results suggested that the increased JA content,as a signal molecule,up-regulated the expression level of PIP gene in dehydrated root and increased water uptake capacity of roots and guaranteed water balance of leaves,and then contributed to a relatively high Pn.Partial root-zone irrigation combined with relatively high plant density(225000 plants·hm-2)is an important agronomic alternative for water saving in cotton plantation in the dry land areas.