Effects of soil water stress on expansion of leaf area and development of fruit in fruiting period of greenhouse sweet pepper

Abstract: Taking Catherine that was one variety of Capsicum annuum L. as test materials, the experiment with 4 soil moisture contents was conducted to investigate the effect of different soil water on the expansion of leaf area and the fruit dynamic development of greenhouse sweet pepper in Venlo greenhouse of Nanjing University of Information Science & Technology in 2016. The 4 treatments in the experiment included field water holding capacity of 70%-80% (CK), 60%-70% (light stress), 50%-60% (moderate stress) and 40%-50% (severe stress). Soil water sensor EM50 was used to monitor soil water content. The leaf area expansion dynamics, the fruit development dynamics and the yield of sweet pepper were determined in fruiting period. The results showed that: 1) Leaf and fruit development of sweet pepper experienced 3 stages including slow growth, linear scale growth and stable constant growth stage. With the increase of the water stress, the leaf area and fruit diameter were evidently reduced. Compared with CK, the maximum leaf area, fruit equatorial diameter and longitudinal diameter under severe stress treatment were reduced by 57.48%, 38.83% and 52.85% (P<0.05), respectively. 2) Soil water stress reduced the maximum growth rate of leaf and the fruit diameter of sweet pepper. The maximum of leaf and the fruit growth rate appeared obviously earlier with the increase of soil water stress. The growth rate of fruit equatorial diameter, the growth rate of fruit longitudinal diameter and the leaf relative expansion rate in the late development stage of leave or fruit under light stress were higher than other treatments, but the difference was not significant (P>0.05). 3) Soil water stress prolonged the rapid growth time of leaf and fruit equatorial diameter significantly. Compared with CK, the leaf rapid growth time under light stress, moderate stress and severe stress delayed by 1.18, 1.18 and 1.46 d (P<0.05), respectively. 4) The total number of fruit per plant, the mean fresh weight of individual fruit per plant and the yield per plant were significantly reduced under moderate and severe stress (P<0.05), but the fruit number per plant increased by 23.61% compared with CK under light stress, and the yield was not significantly different from CK (P>0.05). This study indicated that soil water stress decreased the leaf area and the fruit diameter, but light water stress treatment could improve the tolerance to drought stress, promote the late development of leaves or fruits and increase the fruit number of greenhouse sweet peppers. The results provide a reference for the optimal control of the greenhouse sweet pepper environment.