水氮耦合对棉花幼苗根冠生长和水分利用效率的影响

为明确节水灌溉条件下配施氮肥提高水分利用效率(WUE)的可行性,采用分根交替灌溉(APRI)和常规供水(NI)的方式分别培养棉花幼苗,同时配施不同水平氮素(高氮200 kg/hm~2、中氮120 kg/hm~2、低氮80 kg/hm~2),研究了干旱胁迫后棉花幼苗生长、光合作用、根系形态、根冠生物量、瞬时和生物量水分利用效率(WUEi和WUEb)等的变化。结果表明:干旱胁迫显著降低了棉花幼苗的株高、叶面积、光合作用参数净光合作用速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs)]、蒸腾耗水量和根冠生物量,但显著增加了棉花幼苗的根冠比、根系长度(总根长和直径2 mm的细根长度)和根系表面积;同时干旱处理也显著增大了WUEi和WUEb。与正常施氮(中氮处理)相比,增施氮肥促进了棉花幼苗株高、茎粗、叶面积、Pn、Tr、Gs、蒸腾耗水量以及根冠生物量、总根长、根系表面积等的增大,显著降低了WUEi但未改变NI处理的WUEb;减施氮肥则加大了干旱对棉花幼苗生长、光合作用能力和根冠生物量积累的抑制程度,但在干旱条件下提高了WUEi和WUEb。与NI处理相比,APRI处理的棉花幼苗株高、茎粗、叶面积、Pn、Tr、Gs、根冠生物量、总根长和根系表面积增加,蒸腾耗水量减少,WUEi和WUEb增加。综上,APRI配施氮肥处理可以减轻干旱对棉花幼苗生长和根系形态的抑制程度,并提高WUE;虽然在干旱条件下APRI配施低氮处理具有最大的WUE,但APRI配施高氮处理棉花幼苗的根冠生长最好。

Effect of Coupling of Water and Nitrogen on Shoot and Root Growth and Water Use Efficiency of Cotton Seedlings

Alternative partial root-zone irrigation(APRI) and conventional water supply(NI) were used to cultivate cotton seedling,coupling with different nitrogen levels(high nitrogen 200 kg/ha,medium nitrogen 120 kg/ha and low nitrogen 80 kg/ha),in order to estimate the feasibility of improving WUE after nitrogen application under water saving irrigation condition.The effects of growth,photosynthesis,root morphology,root and shoot biomass,instantaneous and biomass water use efficiency(WUEi and WUEb)and so on were measured.The results showed that drought stress significantly reduced the plant height,leaf area,photosynthetic parameters including net photosynthetic rate(Pn),transpiration rate(Tr) and stomatal conductance(Gs)],water consumption by transpiration,root biomass and shoot biomass,but significantly increased the ratio of root to shoot,root length(including total root length and <2 mm fine root length) and root surface area in cotton seedlings.Drought stress,however,significantly increased WUEi and WUEb.Compared with medium nitrogen treatment,high nitrogen increased the plant height,stem diameter,leaf area,Pn,Tr,Gs,water consumption by transpiration and root/shoot biomass of cotton seedlings,at the same time,improved total root length and surface area of the roots,but decreased WUEi and did not change WUEb in NI treatment.Low nitrogen improved the inhibition of growth,photosynthesis and accumulation of root/shoot biomass induced by drought but increased WUEi and WUEb under drought stress.Compared with NI treatment,APRI increased the plant height,stem diameter,leaf area,Pn,Tr,Gs,root/shoot biomass,total root length and surface area,but decreased water consumption by transpiration.Therefore,APRI increased WUEi and WUEb in cotton seedlings.The combined treatment of APRI and nitrogen may improve adaptation of growth and root morphology to drought stress and then it will increase WUE.Although WUE is higher in APRI coupling with low nitrogen treatment,cotton seedlings growth is better in APRI coupling with high nitrogen treatment.