| Considering the water-consuming process in plant body is what the biological water saving technique should research into. This process includes crop roots' absorbing water from soil, transfer, transpiration and synthesis of assimilative products. Contrast of multi-index can expose the varying characters and relationships between them, which is the basis of further learning the mechanism and developing the technology of biological water saving. But handling many indexes at one time had difficulties in sampling, measuring and absence of labors etc., which somewhat explains why we usually study a few indexes at a time. So few researches have been carried out to systematically compare the changes and relationships of many different indexes. Citrus grows most in the southern areas of China, where is abundant of rainwater and hardly severe drought happens. All the time, few researches of water saving were done for citrus. Recently, in the development of citrus industry, it exposed the problem of seasonal drying which significantly influences the production and quality of citrus fruit. Based on serving the citrus industry, study was carried out to systematically compare the varying characters of multi-index under drought stress and scientifically determine the reasonableness of the indexes for use. Also, this research can provide some basic data for further studying the biological water saving techniques of citrus.Two years old of Citrus sinensis(L.) Osbeck cv. Fengjie 72-1 navel grafted onto Poncirus trifoliate(L.) Raf. was grown in container, in which the soil medium is composed of sand, peat and rice hull (5:4:1). Sustained drought stress was imposed on the plants and every 0, 2, 4, 6, 8, 10, 12, 14 day five plants were picked out to determine the soil water content and water potential (1), relative water content (RWC), chlorophyll content (Chi), activities of catalase (CAT), peroxidase(POD) and superoxide dismutase (SOD), content of malondialdehyde (MDA), free proline (Pro) and abscisic acid (ABA) of the leaves. Three aspects were studied through statistic analysis and systemic comparison: a) changing rules of the physiological indexes with soil water content; b) the relationships between different physiological indexes; c) selection of the proper physiological indexes which can properly reflect the soil and plant water status.1 Changing rules of citrus physiological indexes with soil water content and measurementThe results indicated that soil water content greatly affected both the plant water level and Chi content. Both ψ1 and RWC reduced with the decrease of soil water content and the contribution of soil water to plant water change accounted for about 70-90%. In addition, ψ1 and RWC changed most when soil water content decreased to 19% around. But the content of Chi showed increasing with the decrease of soil water content. And chlorophyll a (Chla) and total chlorophyll (Chit) contents were affected more greatly than chlorophyll b (Chlb). The contribution of soil water to Chi content change was about 50%, and When soil water content was aout 30%, there was an extreme change appeared for Chi content.Both activities of three protective enzymes and MDA content significantly correlated with soil water content. But it was not quite the same for them to respond to the change of soil water content. With fall of soil water content, activity of CAT decreased and activities of POD and SOD increased, and MDA content declined a little. The contribution of soil water to activity change for three enzymes was about 30%, and only 6.5% for MDA content change. The CAT, POD and SOD activities changed distinctly when soil water content was about 40%, 25% and 30% respectively.Contents of Pro and ABA were affected greatly by the change of soil water content. Both of them increased with decrease of soil water content. The contribution of soil water to Pro content change was about 55% and that of ABA was about 30%. And both changed markedly when soil water content was about 15-20%.2 Relationships be... |
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