番茄果实及茎秆微变化对分根区交替灌溉的响应

研究日光温室番茄果实直径以及茎秆直径微变化在不同天气状况的变化规律以及其与分根区交替灌溉(alternate partial rootzone irrigation,APRI)以及固定部分根区滴灌(fixed root-zone drip irrigation,FDI)条件下不同根区土壤含水量的关系,可为根据茎秆直径和果实直径微变化指导部分根区灌溉决策提供理论依据。该研究利用LPS-05MD植物生理监测系统对日光温室APRI和FDI处理下盛果期的果实直径与茎秆直径的微变化进行了连续观测。结果表明:晴天番茄果实直径以及茎秆直径微变化幅度较阴天显著(P0.05)。在盛果期,番茄果实直径日增长量(maximum daily increase of fruit diameter,MDIFD)与土壤水分含量关系不密切(R2=0.30,P=0.164),然而MDIFD随着日平均太阳辐射强度的增加而显著增大(R2=0.64,P=0.018);盛果期APRI和FDI处理下茎秆直径日最大收缩量(maximum daily stem shrinkage,MDS)与参考作物蒸发蒸腾量(ET0)存在显著线性正相关(R2=0.38,P0.0001);APRI处理MDS与ET0比值(MDS/ET0)随着根区平均土壤含水量的增加而线性增加,并且MDS/ET0与干燥侧(R2=0.59,P0.01)以及湿润侧土壤含水量(R2=0.88,P0.001)均呈现极显著线性相关关系(P0.01),且以湿润侧的关系极显著(P0.001);FDI处理下,MDS与ET0比值(MDS/ET0)随着湿润侧根区平均土壤含水量的增加而显著线性增加(R2=0.61,P0.001),而MDS/ET0与干燥侧土壤含水量无显著线性相关关系(R2=0.02,P=0.64)。该研究揭示了APRI以及FDI处理下日光温室条件下果实直径和茎秆直径微变化的机制,可为该灌溉方式下科学灌溉制度的建立提供依据。

Effect of alternate partial root-zone irrigation on fruit and stem diameter of tomato

Abstract: Studying the variation of fruit and stem diameter is critical for optimizing irrigation schedule of tomato under alternate partial root zone drip irrigation (APRI) and improving water use efficiency in the green house. A plant physiology monitoring system (LPS-05MD) was used to measure the variation of fruit diameter and stem diameter during the fruiting stage of tomato under three different irrigation regimes: conventional drip irrigation (CDI), APRI and fixed partial root-zone irrigation (FDI). The soil under CDI were irrigated to 100% field capacity (FC) of the root-zones (from 0 m to a maximum depth of 0.40 m during the fruiting stage) by the drip irrigation system when the soil water content (SWC) in the root-zone reaching 80% FC. During the same day, the APRI and FDI treatments received about 2/3 of the irrigation amount for CDI, but only irrigated to one part of the root-zones (approximately 1/2 of the whole root-zone). For APRI, the irrigated root zone was alternatively changed from one side to another and consequently resulted in the SWC of different sides alternately high and low; whereas in FDI treatment, only the fixed side was irrigated and the other side was kept drying during the growing season. Results indicated that the variation of fruit diameter was significantly higher (P<0.05) in sunny days with high solar radiation rate than that of cloudy day with low solar radiation rate. The increase of tomato fruit diameter per day was not significantly linearly related to average SWC of the whole root zone (R2=0.30, P=0.16), but significantly related to the average solar radiation rate (R2=0.64, P=0.018). Previous studies indicate that the magnitude of MDS (maximum daily stem shrinkage) are not constant over a period of days with the same water status but different environmental conditions, and absolute MDS values registered without considering the evaporative demand might be meaningless. Based on this, there was a positive linear relationship between MDS and ET0 (R2=0.38, P<0.001), and the relationship between the value of MDS divided by ET0 (MDS/ET0) with SWC was significant different than MDS with SWC, which indicated that normalizing the absolute MDS values by environmental parameters, such as ET0, can help to indicate the soil water status precisely. Contrary to the previous results that MDS values increase in response to drought stress, in this study, MDS of APRI decreased with increasing water stress. This might be explained by the low resistance of water flow and high hydraulic capacitance of the tomato cultivar as well as the special physiological responses under APRI. For APRI, MDS/ET0 had a close relationships with SWC in the drying and wet root-zone (R2=0.60, P=0.006 and R2 =0.88, P<0.001, respectively), which indicated that MDS normalized by ET0 under APRI was influenced both by SWC of drying side and wet side, and predominantly by the irrigated root-zone. Similarly, MDS/ET0 in FDI treatment was closely linearly related with the SWC in the irrigated root-zone (R2=0.61, P<0.001), but not with the fixed drying side (R2=0.02, P=0.64). This phenomenon can be explained by the decay of roots in the drying root-zone and the diminishment of the chemical signal generated from the drying roots of FDI. To the best of our knowledge, no study has been done to investigate the relationship between MDS (or MDS/ET0) and SWC of different root zone under APRI. The data in this study can help to reveal the mechanisms of variation of fruit diameter and stem diameter, as well as providing useful information for optimizing irrigation schedule of tomato under APRI grown in greenhouse.