| The2-year-old young apple trees (Malus pumila Mill. Yanfu3) were used as the test material and methods of two different irrigation testing (irrigation methods and irrigation water amount) and randomized block were adopted in this pot experiment. The two irrigation methods, conventional water (CI, which gave full watering to all the soil) and alternative partial root-zone irrigation (APRI, which gave alternate irrigation for1/2area of the pot surface), were designed. There were four treatments in conventional water methods which respectively were C1, C2, C3and C4and irrigation water amount were50%,37.5%,25%and12.5%corresponding to evaporation from water surface. At the same time, APRI also had four treatments which were respectively A1, A2, A3and A4, and their irrigation water amount was half of the corresponding CI treatment. It were studied the plant growth and development status, the changes of soil moisture, plant photosynthesis changes and stem flow rate changes of the apple trees which were handled by different water treatment with two different irrigation ways, which was carried out in a waterproofed shelter from April to November in2013.1. Under two kinds of water treatment, apple saplings’height of CI and APRI were significantly reduced. The treatment C2, C3, C4of CI respectively reduced by18.76%,35.87%,38.72%than the control of C1. The treatment A2, A3, A4of APRI respectively decreased by22.82%,24.62%and45.05%than the control of A1. The growth of young stem were significantly reduced with the treatment C2, C3, C4respectively inhibited by57.97%,69.28%and91.92%than the control of C1and the treatment A2, A3, A4respectively decreased by37.67%,68.15%and73.29%than the control of A1respectively. The growth of young shoot of CI and APRI were significantly inhibited. The treatment C2, C3, C4respectively inhibited by9.76%,31.56%and50.1%than the control of C1and the treatment A2, A3, A4respectively decreased by13.25%,42.4%, and63.58%than the control of A1respectively. The increment of new shoot weights was decreased. The treatment C2, C3, C4respectively inhibited by29.8%、37.2%、47.8%than the control of Cl and the treatment A2, A3, A4respectively decreased by39.3%、62.9%、65.9%than the control of A1respectively. At the same time the leaf areas per plant of CI and APRI were outstandingly decreased. The treatment C2, C3, C4respectively inhibited by13.8%,26.61%and51.34%than the control of C1and the treatment A2, A3, A4of APRI respectively decreased by22.61%,44.5%and58.62%than the control of Al respectively. The plant height, stem diameters, length and diameter of young shoots were slowly increased and leaf area per plant was decreased after a gradual increase along with the extension of water stress time. With the irrigation water being cut in half amount, the plant height, stem diameter, the length and weights of new shoot and leaf area of APRI treatments decreased in all aspects but the decrease was slight. And with same irrigation quantity, the young apple trees of APRI treatment grew better than CI treatment.2. Water stress affected the photosynthesis of apple saplings. Under condition of same water irrigation the net photosynthetic rate of alternative partial-root irrigation was12.1%higher than that of conventional watering. But when the irrigation amount decreased25%, the photosynthetic rate of A2was only2.2%lower than C3which was conventional watering. The average transpiration rate of CI was the higher, and the average transpiration rate of A1, A2, A3and A4were respectively decreased6.5%,12.1%,32.1%and38.0%than C3. The WUE value of A1and A2were higher, respectively13.2%and6.9%higher than C3. The WUE value of A3and A4were relatively lower, respectively3.4%and12.2%lower than C3.3. Water stress affected the distribution of apple saplings biomass in the aboveground and underground part. With the extension of water stress time, the young apple trees’ aboveground biomass, underground biomass, total biomass and the root-shoot ratio in two different irrigation method presented a gradual increase trend, and the biomass accumulation rate became gradually slow and the root-shoot ratio became gradually higher with the enhance of water stress. The root-shoot ratios of the treatment C2, C3, C4respectively increased by10.3%,28.2%and46.0%than the control of C1and root-shoot ratios of the treatment A2, A3, A4increased respectively by22.8%,34.5%and40.1%higher than the control of A1. With the irrigation water was cut in half amount, the root-shoot ratios of APRI were increased by6.45%,18.5%,11.9%and2.1%than CI.4. The stem water potential and leaf water potential could represent the water status in vivo and soil water regime of two different treatment young apple trees. As the water stress time became longer and its extent increased, the stem and leaf water potential gradually reduced. The stem water potential was higher0.10-0.20Mpa than leaf water potential at every corresponding moment of the same treatment. The variation trend of stem water potential and leaf water potential were similar with that of soil water potential, which all showed a tendency to decrease, but there was a lag effect relative to soil water potential.5. The diurnal changes of sap flow rate of young apple trees under two different water treatments were mono-peak curves. Whether normal irrigation or water stress, the sap flow rate of the apple trees generally started a launch at7:30am or so, reaching the maximum at about12:00and finally ending at about18:00pm or so. The sap flow rate of CI and APRI were respectively decreased with water stress severity. Treatment C2, C3, C4respectively decreased by5.63%,32.5%and42.8than the control of C1and the treatment A2, A3, A4respectively decreased by22.8%,34.5%and40.1%than the control of A1respectively. The day-to-day variation of sap flow rate on young apple trees under different water treatments obviously showed alternative circadian rhythm. Comparing two kinds of irrigation methods, we could find that with irrigation water cut in half amount the average stem flow rate per day of alternative partial root-zone irrigation treatment A1-A4were12.99%,17.83%,17.33%,24.62%correspondingly lower than conventional watering treatment C1-C4. |
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