4种杂交杨对土壤水分变化的生态学响应

ECOLOGICAL RESPONSES TO SOIL WATER CONTENT IN FOUR HYBRID POPULUS CLONES

以田间持水量的100%(T1,对照)、70%(T2)、50%(T3)和30%(T4)为4个水分处理梯度,比较研究了4种不同品系的杂交杨(Populus)——15-29(P.trichocarpa×P.deltoids)、DN-2(P.deltoids×P.nigra)、DN-14274(P.deltoids×P.nigra)和R-270(P.deltoids×P.nigra)在不同水分处理和不同处理阶段对水分亏缺的反应。结果表明,4种杂交杨品系对水分亏缺较敏感,都通过关闭气孔、降低叶面积以有效地调节水分的散失,降低光合速率、蒸腾、水势,增加水分利用效率,改变生物量的分配等一系列生理适应机制以及形态策略,来应对不同程度的水分亏缺,只是不同品系的适应程度不同。在生物量分配上,R-270主要降低叶干重,而其它3个品系的叶、茎和根干重全部降低;随着水分亏缺的加重,15-29和R-270的根冠比增加,根部获得更多的同化物分配,从而有利于水分的吸收,增加其抗旱性。DN-2的碳同位素组成δ13与水分利用效率呈显著正相关(r=0.631,p<0.01)。而R-270的δ13与水分利用效率呈负相关,但不显著,只有在处理T4下呈显著负相关(r=-0.732,p<0.01),表明土壤水分影响了碳同位素的分馏,不同品系相反的结果表明同位素分馏的遗传变异。与T3和T4相比,T1和T2处理的苗木具有较高的生物量、叶面积、光合速率、蒸腾、水势以及气孔导度,说明4个杂交杨品系在充足或适当的灌溉条件下具有较高的生产力。在T3和T4处理下,4个品系表现出不同的生存策略,但生产力均较低,因此在干旱胁迫下很难形成高生产力。与DN-2和DN-14274相比,15-29和R-270对水分胁迫表现出更强的适应性反应,具有较强的抗旱性,可用作防护林品种。

Aims Pot experiments were conducted to investigate effects of water deficit and duration of the deficit （0, 15, 36 and 14 days recovery） on four hybrid Populus： 15-29 （P. trichocarpa × P. deltoids）,DN-2 （P. deltoids × P. nigra）, DN-14274 （P. deltoids × P. nigra） and R-270 （P. deltoids × P. nigra）.Our objective was to examine the responses of Populus plants to soil water deficit by analyzing eco-physiological, morphological, and growth characteristics, as well as several parameters of plant performance. Methods Seedlings were exposed to four treatments： 100%, 70%, 50% and 30% of soil field water capacity （treatments T1-T4, respectively）.Important findings The four hybrids were sensitive to water deficit. All developed physiological adaptive mechanisms as well as configurational strategies to cope with water shortages to different degrees by closing stomata and reducing leaf number and leaf area to regulate water loss, by depressing net photosynthetic rate （Pn）, transpiration rate （Tr） and leaf water potential （ψ） to enhance water use efficiency （WUE）, or by changing allocation of biomass productivity （Bp）. Under water stress, R-270 only decreased its leaf dry weight but the other three hybrids decreased their dry weight of leaf, stem and root. With declining soil moisture, root/shoot of 15-29 and R-270 increased, implying the roots obtained more carbohydrates, which favors water absorption. Carbon isotope composition （δ13） of DN-2 was significantly positively correlated to WUE, but δ13 of R-270 was significantly negatively correlated to WUE. Pn, stomatal conductance （Gs）, Tr,ψ, biomass and canopy areas of the seedlings in T1 and T2 are higher than those in T3 and T4, suggesting that the four hybrids can obtain high production in arid areas under sufficient-moderate irrigation. Lower Pn, Gs, Tr,ψ, biomass, canopy areas and higher WUE of the seedling in T3 and T4 indicate that the four hybrids can develop survival strategies under water stress,but biomass production was negatively affected. Clone 15-29 and R-270 showed a stronger adaptive response than DN-2 and DN-14274 under water stress, implying they have greater drought-resistance ability.