Effects Of Water Stress At Rootstock And Paritial Rootzones Irrigation At Fuji Apple Trees On Hydraulic Conductivity

In this study, we use the material of apple rootstock Malus hupehensis seedlings toexperiment materials; use the method of pot water control under the condition of water stressand different potassium levels, study hydraulic structure characteristics of seedlings.Meanwhile, we use field tree (Fuji apple tree) for materials, research paritial rootzonesirrigation effects on the hydraulic characteristics of the tree. The following results wereobtained in this study:1. Water deficit greatly decreased hydraulic conductance of root, leaf and plant, leaf areaspecific conductance of leaf and plant, sapwood area specific conductance of plant of Malushupehensis, the leaf area specific conductance of leaf in the moderate and severe water stressreduced to the35%and29%of normal water conditions respectively.2. On the normal irrigation conditions and potassium addition can greatly enhancedhydraulic conductance of root and plant; greatly enhanced leaf area specific conductance ofroot, leaf and plant; also greatly enhanced sapwood area specific conductance of plant ofMalus hupehensis. The leaf area specific conductance of leaf in the moderate and highpotassium level were increased by17%and lowered27%compared with low potassium levelrespectively. In the severe water deficit, stomatal conductance in the moderate potassiumlevel increases by28%compared with low potassium level. Water deficit reduced stomatialconductance(GS), however, potassium can decreased this result on some levels.3. Taking thirteen years Fuji apple trees as experiment material, we studied the effects ofall root drying irrigation(NI), partial root zone irrigation(PDI), conventional irrigation(CI),three irrigation modes on the water potential, gas exchange, leaf and shoot hydraulicconductivity characteristics in the field conditons. The results indicated that leaf waterpotential and stem water potential reach the lowest valve in July of Fuji apple trees, diurnalvariations of water potential at reach the lowest valve in the14o 'clock, diurnal variations ofleaf water potential and stem water potential presented "V" type.4. The leaf hydraulic conductance and leaf area specific conductance have graduallydecline as the increase of the degree of drought, leaf hydraulic conductance of PDI and NIreduced13.27%and42.01%, shoot hydraulic conductance of PDI and NI reduced3.01%and34.36%compared with that of CI. But compared with CI and NI, leaf area specific conductance and shoot area specific conductance of PDI are enhanced by14.32%and14.43%,96.12%and16.55%, respectively. PDI has a bigger leaf area specific conductance comparedwith CI and NI, however, value of RWC is between the two, it showed that in a certain RWCrange, increase of leaf area specific conductance at the expense of RWC. Compared with CIand NI,WUE of PDI greatly improved29.08%and26.82%, and its max net photosyntheticrate, apparent quantum efficiemty and dark respiration rate are between the CI and NI. Thisshows in the semiarid areas of Northwest, PDI treatment can improve water use efficiencywithout influence the apple tree normal physiological indices and utilization rate of solarradiation.5. Measured with the high pressure flow meter (HPFM), study the effects of water deficiton hydraulic architecture and pressure-volume curve water parameters of Malus hupehensisand Malus prunifolia. The results indicated that water deficit decreased hydraulic conductance,leaf area specific conductance, sapwood area specific conductance on root of Malushupehensis and Malus prunifolia. But there are certain differences compared to the rootstock.On the condition of suitable soil moisture and severe drought, leaf area specific conductanceon root of Malus hupehensis is95%and92%of Malus prunifolia respectively, sapwood areaspecific conductance on root of Malus hupehensis is52%and62%of Malus prunifoliarespectively, aspects of leaf area specific conductance and sapwood area specific conductanceon root, Malus prunifolia has larger value than Malus hupehensis. Drought stress maydecrease decreased hydraulic conductance of root, and then affected gas exchange of theground part. On the condition of suitable soil moisture and severe drought, compared valuesof ψs^tlp,ψs^sat, RWC^tlp, ROWC^tlp,ε＇of Malus prunifolia with Malus hupehensis, Malusprunifolia was on a low level, values of Va of Malus prunifolia was on a high level. Used bythe subordinate function comprehensive estimating analysis, pressure-volume curve waterparameters, value of Malus prunifolia was larger than Malus hupehensis's, b value betweenMalus prunifolia and Malus hupehensis have no obvious difference. On the condition ofsuitable soil moisture and severe drought, Malus prunifolia reflects the water strategy whichwas better than Malus hupehensis. Pressure-volume curve water parameters in plants canadjust accordingly with environment. Studied with pressure-volume curve water parameters,Malus prunifolia is better than Malus hupehensis in the abilities of maintaining turgor of andthe drought resistance.