Study And Appraise On The Stress Of Poplar Clones

In order to analyze the changes under stress and provide a scientific and theoretic basis for generalization on large area of poplar plantation construction(REC), stem growth rhythm, physiological and biochemical characteristic of photosynthesis(Pn), transpiration(Tr), leaf chlorophyll content (Chl), Leaf water potential (Lwp), cell membrane penetration (Relative electric conductivity)(REC), and super oxide dismutase activity (SOD) of seven poplar clones of A50, A69, Chen-1, B33, B34, B40, B53, and I-107 (CK) was control under drought stress, flooding stress and salt stress from mid-May to mid-September, 2005 in Shandong agricultural university were researched. The results were as follows:Under drought stress: (1) Leaves of all the clones were wilted on the fifth day of drought stress treatment, Soil water potential decreased to -0.46 ~ -2.58 MPa, and A69, B40, A50 were abscised. Seedlings began to die on the seventh of drought stress, Soil water potential was -0.99 ~ -2.74 MPa at this time. (2) Diurnal maximum Pn of all the clones appeared at 10:00 am, and daily Pn were decreased along with soil moisture condition deteriorated. (3) Chl of all the clones showed a downward trend along with the soil moisture condition droughted, and Chl of most varieties was rapidly descended under badly water stress, but A50,B34,B53 was changed little. (4) Maximum Tr appeared at 10:00~14:00 in the period of soil water controlling days, and as water stress aggravated, the maximum Tr appearing time aheaded. Diurnal fluctuation of Tr changed acutely at prior drought stress period and smoothly under the severe drought stress in the later days. (5) Lwp was larger in the morning, and then decreased smoothly. Minimum Lwp appeared at 14:00~16:00, and then it recovered gradually; Daily Lwp decreased gradually under drought stress. (6) REC was increased in the gradient of drought stress. (7) SOD increased first, and then decreased under middling and bad drought stress, conpaired with that at favourable soil moisture condition.Under flooding stress: (1) Seedling stem increment rate of all the clones was decreased as flooding stress prolonged. (2) Pn of all the poplar clones were sensitive under flooding stress, and changed acutely at the prior period of flooding stress, but gently at the anaphase. (3) Chl dropped greatly under flooding stress. After one month's flooding stress, the leave changed yellow with a mean Chl content decreased 74.6%, and then desended slowly in the later flooding days. (4) Tr under flooding stress was complicated. Clones of A69 and A50 showed a rhythm of decreased-augmented-decreased, Chen-1, B34 and B40 decreased-augmented-increased, and I-107, B33 and B53 decreased-decreased-augmented. (5) Lwp of all the clones was in a rhythm of decreased-decreased–increased in the period of flooding treatment. In the first stage of one month's flooding stress, Lwp dropped greatly, then desended smoothly in the second stage of two month's flooding stress, compaired with CK. Lwp recovered in the third stage of three month's flooding stress, but it was still less than CK. (6) REC of all the clones increased under flooding stress treatment that in the first stage of one month's treatment the increasement was unconsistent, and in the second stage of two month's treatment the increasement was little, but in the third stage of three month's treatment the increasemnt was asended. (7) SOD of all the clones was increased-decreased-increased. In the first stage of one month's treatment, SOD increased compared with CK, but was less than that after two and three month's treatment.Under salt stress: (1) The height of poplar clones seedling was decreased as the concentration of NaCl augmented. (2) Pn of all the poplar clones was less than CK in the period of salt stress. (3) In May and July, Chl of most clones decrease as the concentration of NaCl increased. Content difference of Chl became larger as the treatment period prolonged. But I-107, Chen-1 showed an exceptional that at the early period under the treatments of 1‰and 3‰Chl augmented, but the later period of treatment Chl decreased. (4) Tr was decreased compared with CK, and the degree of decline was augmented as treatment period prolonged. (5) In May, Lwp was different between all the clones and was gradually decreased as the concentration of NaCl was increased. And in September, Lwp of all the clones was increased at a relative stability level, and the difference was little, compared with CK. (6) REC was increased under salt stress and asended with the treatment period prolonged. (7) At gentleness salt stress, SOD was increased, and at serious salt stress, SOD was decreased. In May and July, SOD of all the clones increased first, and then decreased. And in September, SOD of all the poplar clones was decreased, as the concentration of NaCl increased.By the method of membership function, a lot of evaluation index were used to appraise all the clones'stress resistance and eco-physiological adaptabilities. Sequence of drought resistance ability was: B34 > I-107 >陈1 > B33 > B53 > A69 > B40 > A50, the sequence of flooding resistance ability was:陈1 > A50 > A69 > I-107 > B53 > B34 > B40 > B33, and the sequence of salt resistance ability was: I-107 >陈1 > B33 > B34 > B40 > B53 > A45.