Growth,Development And Physiological Response Of Chilli Pepper Under Water Stress

This experiment use two chilli pepper cultivars Duojiao and Xinxiang No.8 that commonly grown in Shaanxi Province which is pepper producing area as the test materials to study the effects of water stress on the root morphology and other physiological indexes.The test use pot experiment,set up four levels of controlling soil relative water content:T1(40-50%),T2(50-60%),T3(60-70%),T4(70-80%),(the check)CK 80-90%,the main result is followings:1.Water stress could suppress the growth of chilli pepper root.The rate of increase of total root length per plant,root volume,root surface area,root tips number,root cross number,root fork number,root fresh weight and dry weight decrease obviously in 20 to 40 days of water stress,even appear negative growth,suggests that in this time,the chilli pepper root is most sensitive to drought stress;The treatments 40%-50%and 50%-60%suppress the growth of chilli pepper root in the whole period of water stress.The treatments 60%-70%and 70%-80%suppress the growth of chilli pepper root mostly in 20-40 days of water stress.In the whole period of water stress,the root shoot ratio and root average diameter of each treatment were higher than those of the control,sugessts that under water stress,the root of chilli pepper grow faster than aboveground part.Water stress is not conducive to the growth of fine root and the emergence of lateral root.Under the same water stress,the root growth of Xinxiang No.8 in all stress treatments was inhibited to a greater extent than Duojiao.2.Water stress could inhibit the growth of aboveground part of chilli pepper,and plant height was inhibitied to a greater extent than stem diameter.Under water stress,the organic matter of photosynthesis are mainly supplied to root growth,but the water were mainly supplied to the abo-veground part.3.In earlier stage of water stress,the soluble sugar,proline(Pro)content of chilli pepper increased,but in later stage of water stress,the content of this two decreased.The most dramatic changes occured between 20-40 days of water stress.In the different treatments,it performed that 40%-50%>50%-60%>60%-70%>70%-80%>80%-90%.The time that soluble sugar and proline(Pro)start to decline of Xinxiang No.8 is earler than Duojiao.Water stress accelerated the malondialdehyde(MDA)content increased,Xinxiang No.8 increased more significantly than Duojiao.Soluble protein(Pr)content of the two specise were all decreased under water stress.4.In earlier stage of water stress,protective enzyme activity in chilli pepper increased,but later,it decreased.Under the treatments of 60%-70%and 70%-80%,Duojiao can maintain higher enzyme activity in a longer period of time.Under the treatments of T1 and T2,the protective enzyme system of Duojiao hurt less than Xinxiang No.8.5.Water stress inhibite net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs)of chilli pepper.Pn showed a sharp decline in 20 to 40 days of water stress,in earlier stage of water stress,the decline of Pn is mainly caused by stomatal limitation,in the later,the decine of Pn is mainly caused by non stomatal limit.From stomatal limitation to non stomatal limitation,Xinxiang No.8 need more time,the ability of the regulation of the photosynthetic system under water stress of Duojiao is Stronger than X,inxiangNo.8.Under water stress,chlorophyll content of chilli pepper decreased.During a day,photosynthetic system of chilli pepper is mainly damaged at 14:00-15:00.6.The fruit number and yield per plant decreased with the loss of soil moisture.Under water stress treatments,the inhibition degree of yield per plant in Duojiao were less than that in Xinxiang No.8,this showed that the drought tolerance of Xinxiang No.8 is less than that of Duojiao.