干旱胁迫对大头茶,栲树幼苗光合,蒸腾速率及其解剖结构的影响

研究了常绿阔叶林树种大头茶和栲树一年生实生苗对干旱胁迫的反应.结果表明:胁迫苗叶形态,解剖特征均向耐旱方向演化,生长下降.叶凋落量增加,而根/冠比增加,相对比存活时间延长.与对照比较,胁迫苗大头茶、栲树蒸腾速率分别降低31.72%和49.23%,但水分利用率却分别增加了7.83%和27.48%,光合速率随叶水势下降而下降.胁迫苗在比其相应对照苗叶水势更低时,仍继续维持较高的光合速率.干旱胁迫的结果使大头茶、栲树幼苗的抗旱能力得到了显著的改进和提高.

DROUGHT STRESS ON PHOTOSYNTHESIS, TRAN SPIRATION AND STRUCTURES OF GORDON IA ACUMEN ATA AND CASTANOPSIS FARGESI1 SEEDLINGS

One-year old Gordoniata aciiminaia (Ga) and Caytsiiut/isin fargettu(Cf) seedlings were used to inves tigate the potential for modifying their drought tolerance. The photosynthesis, transpiration, water-using efficiency, morphological characteristics, growth and biomass allocation of Ga and C.f seedlings were evaluated following exposure to drought stress (Ds). Seedlings were exposed to 8 weeks of DS, watered only when pre-dawn leaf water potential fell bellow -I. 4 MPa. A control group seedlings was kept well watered. Under drought stress, the morphological characteristics of the two species seedlings tend to increase their drought tolerance, but the growth of their stems and shoots are inhibited considerably and much less than that of their roots, therefore, root/shoot ratios of the two species' seedlings are increased in different degrees, namely, Cf (27. 08 % 1 and Ga (18. 18% ); Both of the photosythesis and transpiration of Ga and Cf seedlings are reduced with the decreasing of their leaf water potentials, bur their water using efficiencies are increased 7.83% (Ga)and 27. /I8;% (Cf) respec tivelying. Seedlings exposed to DS continued the photosynthesis to much lower leaf water potentials than controls. These responses all indicate significant improvement in Ga and C'f drought tolerance as a result of DS.