Effect Of Water Stress On Spike Leaf Physiological Characters And Yield Of Oats

In this study, three pot experiments were conducuted under rainproof shelter condition. First, we studied water stress on oat spike differentiation process and yield in panicle initiation stage. Second, we studied water stress on plant growth, photosynthetic characteristics, spike physiological characteristics and yield of two different drought resistance oat types in jointing, heading and filling stage. Third, we studied the photosynthetic contribution of different organs to grain under water stress in filling stage by cut leaf, package the spike and package the stem. The main results showed as follows:(1) Water stress shortened the time of early growth cone period, growth cone elongation period and branch differentiation period in early spikelet differentiation stage. Differentiation speed accelerated at the spikelet differentiation stage, the time of spike differentiation process under water stress consistent with normal irrigated treatment. Water stress result in the incomplete differentiation of spikelet differentiation stage, flowers fell off and not fully developed in late differentiation,which led to the decrease of grain setting rate and yield.(2) Water stress led to the decrease of leaf chlorophyll relative content (SPAD),photosynthetic rate and transpiration rate of oats. Water stress had the greatest effects to photosynthetic rate on water sensitive variety in filling stage, while water stress had the greatest effects on drought resistant variety in heading stage. At the same water treatments, photosynthetic rate of drought resistant variety was higher than that of water sensitive variety, and the rangeability was less than water sensitive variety. Compered with normal water supply, water stress made the blade midday depression in advance.(3) Water stress increased Chlorophyll initial fluorescence value (FO) of oats leaf, reduced variable fluorescence (Fv) and fluorescence (Fm) increased. As water stress increased, leaf electron transfer efficiency (ETR) and actual quantum yield (ΦPS II) decreased accordlingly. Under normal water supply, chlorophyll fluorescence photochemical quenching parameters (qP) and electron transfer efficiency (ETR) had significant correlation with F0、Fm、Fv、Fv/Fm and Fv/F0. There were significant correlations among other fluorescence parameters. The minimum diurnal variation of the chlorophyll fluorescence parameters Fv/Fm came earlier under water stress than normal water supply.(4) Under water stress, the content and rangeability of soluble protein and free proline in spike and glume were both increased in heading and filling stage. The rangeability of osmotic adjustment substances in heading stage was greater than that in filling stage. The activity of SOD and POD both increased early and decreased later as water stress increased. Under the same water treatment, the activity of SOD and POD of Mengyan1were significantly higher than that of Bayou3. Water stress led to the malonaldehyde content (MDA) increased, and the rangeability in Bayou3was greater than that of Mengyan1. The relative conductivity in spike and glume increased as water stress increased. Under severe water stress, the relative conductivity was significantly higher than under nomal water supply at the same growth stage.(5) At heading and filling stage, spike grain weight per plant, thousand kernel weight and yield of oat under water stress were lower than those under normal water supply. Furthermore, yield reduction at filling stage was worse than that at heading stage under water stress.(6) Under water stress, the photosynthesis contribution rate of panicle and leaf to grain were increased3.95%and2.20%than normal water condition, however, the photosynthesis contribution of stem to grain declined.