A Study On The Drought Resistance Of Acer Ginnala,Malus Baccata,Prunus Davidiana And Pyrus Ussuriensis

The ability of drought-resistance of Acer ginnala M.,Malus baccata L,Primus davidiana C. and Pyrus ussuriensis M. were studied under four soil moisture gradients (65.2%,53.1%,40.3%,30.8%) and the continuous soil drought experiments by plant seedlings in pots in greenhouse. The changes of leaf water potential,water deficiency,water-holding ability under drought stress conditions were measured. The water parameters were calculated by using Pressure-Volume technique,also the abilities of maintaining turgor and adjusting osmotic potential of the four species were comprehensively evaluated. The effects of drought stress on photosynthesis,transpiration and water use efficiency were studied. The growth and biomass allocations of seedlings under water stress conditions were measured and analyzed. The results show:(1) Drought-resistance mechanisms of the four species were drought tolerance of dehydration tolerance with low tissue water potential. Under drought conditions,the decreasing degree of water potential is:A. ginnala > P. ussuriensis > P. davidiana. > M. baccata;the water deficiency is A. ginnala > P. davidiana. > M. baccata> P. Ussuriensis;the water-holding ability is A. ginnala > P. Ussuriensis >M. baccata> P. davidiana. (2)A11 of the four species have the abilities of osmotic adjustment and turgor maintenance,but their ability is difference. The ability to maintain turgor and adjust osmosis is :M. baccata> P. ussuriensis > P. davidiana> A. ginnala. The ability of tolerating dehydration is:M. baccata> P. davidiana> P. ussuriensis > A. ginnala. Under drought conditions,the ability of P. davidian's osmotic adjustment is decreasing,the others are increasing. The ability to adjust osmosis is:M. baccata> P. ussuriensis >A. ginnala> P. davidiana. P. ussuriensis,P. davidiana and A. ginnala can adjust osmosis by improving the proportion of bound water,M. baccata adjust osmosis by decreasing the volume of cell and increasing content of solute. The ability of maintaining maximum turgor and turgor is P. ussuriensis > M. baccata> A. ginnala> P .davidiana. The ability of maintaining turgor arose by elastic cell wall is A. ginnala> P. davidiana> P. ussuriensis > M. baccata.(3)With the decrease of soil moisture content,net photosynthetic rate of these four species and transpiration rate have the tendency of decreasing. Under drought conditions,the decreasing degree of transpiration rate and the conduction of stoma is A. ginnala> M. baccata> P. ussuriensis> P. davidiana. The photosynthesis of P. davidiana is the most tolerant to drought stress,P. ussuriensis and M. baccata are at second place,A. ginnala is the least tolerant to drought stress. P. davidiana's water use efficiency has increasing trend,but the other three species have decreasing trends. (4)The A .ginnala's leaves are sensitive to drought,but the others are not. Under drought conditions,A. ginnala's leaf becomes thicker and its leaf area of a plant decrease. The specific leaf area under drought conditions is:A. ginnala> P. davidiana> M. baccata> P. ussuriensis.(5)Under drought conditions,all of the four species have the abilities to adapting drought environment by increasing root biomass. The improving degree of root proportion and root to shoot ratio is:A. ginnala> P. ussuriensis> P. davidiana>M. baccata. (6)In conclusion:the drought resistance of the four species are strong. Under drought stress,the four species can adapt drought environment by different ways.