基质栽培黄瓜叶片水分状况、光合与荧光参数对不同灌水下限的响应

为探明基质栽培黄瓜适宜的灌水下限,实现农艺节水,以黄瓜品种博特209为试材,采用基质盆栽,共设置4个灌水下限处理,即田间持水量的50%、60%、70%、80%,用A、B、C、D表示,灌水上限统一设定为田间持水量的90%,采用TDR350水分速测仪控制基质的水分含量,研究不同灌水下限对基质栽培黄瓜叶片水分状况、光合日变化及荧光参数的影响。结果表明:随着灌水下限的提高,叶片的相对含水量、自由水含量及自由水/束缚水的比值呈逐渐上升的趋势,水分饱和亏、叶片细胞汁液浓度及束缚水含量则呈下降趋势,处理C、D的相对含水量、自由水含量均显著(P<0.05)高于处理A、B,处理A细胞汁液浓度显著高于处理C、D,处理A、B束缚水含量显著(P<0.05)高于处理C、D。叶绿素a、叶绿素b和叶绿素a+b的含量均随灌水下限的升高呈现为先上升后下降的趋势,而类胡萝卜素含量则表现为先下降后上升的趋势,处理C叶绿素a、叶绿素a+b含量显著(P<0.05)高于处理A、B;处理C、D黄瓜叶片的胞间二氧化碳浓度(C_i)的变化趋势基本呈“V”型,而处理A、B的Ci的变化趋势基本呈“W”型;处理A、B、C、D的蒸腾速率(T_r)日变化均呈先上升后下降的趋势,处理B、C、D的Tr在14:00后呈现逐渐下降的趋势,而处理A在12:00后就呈快速下降的趋势;处理B、C、D的气孔导度(G_s)日变化大致呈“M”型的双峰曲线,处理A则呈单峰曲线;处理A、B、C、D叶片净光合速率(P_n)与G_s日变化趋势基本一致,在整个日变化过程中,处理C、D的P_n始终高于处理A、B。F_v/F_m、Φ_PSⅡ、qP随灌水下限的提高呈逐渐上升的趋势,而NPQ呈逐渐下降的趋势。研究结果表明,灌水下限为田间持水量的70%~80%,基质栽培黄瓜叶片的水分状况良好、光合色素含量高、净光合速率大,有利于黄瓜的光合作用,促进黄瓜的生长发育。

Response of leaf water status,photosynthetic and fluorescence parameters to different irrigation lower limits in substrate culture of cucumber

In order to find out the suitable lower limit of irrigation and realize agricultural water-saving, the cucumber variety Bote 209 was used as material in this experiment, and four irrigation water limit treatments were set in potted medium, 50%, 60%, 70%and 80% of field water holding capacity, which were represented by A, B, C and D, respectively. The upper limit of irrigation was set to 90% of field water holding capacity. TDR350 water velocimeter was used to control the water content of the substrate.The effects of different irrigation lower limit on water status, diurnal variation of photosynthesis and fluorescence parameters of cucumber leaves were studied.The results showed that the relative water content, free water content and free water/bound water of leaves increased gradually with the increase of irrigation lower limit, while the water saturation deficit, leaf cell sap concentration and bound water content showed a reverse trend.The relative water content and free water content of treatment C and D were significantly (P<0.05) higher than those of treatment A and B.The leaf cell sap concentration of treatment A was significantly(P<0.05) higher than those of treatment C and D, and the bound water content of treatment A and B was significantly (P<0.05)higher than treatment C and D. The content of chlorophyll a, chlorophyll b and chlorophyll a+b increased firstly and then decreased with the increase of irrigation lower limit, while the content of carotenoids decreased firstly and then increased. The content of chlorophyll a and chlorophyll a+b in treatment C was significantly(P<0.05)higher than that in treatment A and B.The change trend of C_i in treatment C and D was showed as V-shape, while that in treatment A and B was W-shaped.T_r in treatment A, B, C, D firstly increased and then declined, which showed a trend of gradually declining after 14:00 in treatment B, C, D, and a trend of rapid decline after 12:00 in treatment A. G_s showed a double peak curve of “M” type in treatment B, C, D, and a single peak curve in treatment A. The change trend of P_n in treatment A, B, C, D leaves were similar as G_s. During the whole process of daily change, P_n in treatment C and D were always higher than that in treatment A and B. F_v/F_m, Φ_PSⅡ, qP increased with the increase of irrigation lower limit, while NPQ decreased.It was concluded that the lower limit of irrigation was 70%-80% of the field water capacity. In this range, the water content of cucumber leaves under substrate cultivation was good, the content of photosynthetic pigment was high, and the net photosynthetic rate was high, which was beneficial to the photosynthesis and the growth and development of cucumber.