楊樹種間耐旱性差異的生理生化基礎研究(存儲版)
【正文】 ater deficit developed was higher in droughted plants of droughtsensitive poplar genotype than that of droughttolerant ones. And Popularis showed the great capacity in keeping water balance among the four experimented genotypes. Furthermore, the highest cell wall elasticity of Popularis indicates its stressedplants have the advantage of maintaining turgor as water potential declines. After subjected to severe soil drought (30% FFC), leaf proline content of Popularis increased by 40% , implying osmotic adjustment occurred after the onset of water stress. For Berolinensis, its cell wall elasticity was lower than that of Popularis, however, its bound water (Va) increased by 18% after drought treatment and yp100(osmotic potential at saturation), yp0(osmotic potential at turgor loss) decreased by and , respectively. Therefore, Berolinensis may maintain turgor mainly through osmotic adjustment during the period of water stress.Compared with the other two droughttolerant genotypes, cell wall elasticity of Italica and Robusta was low. however, it can be improved certain extent by water stress. Plant water status of Italica and Robusta was greatly affected during the onset of soil drying(predawn leaf water potential decreased by ～) and it recovered after leaf abscission.5. There were two stages in the changes of polyamine and ethylene biosynthesis after drought treatment:The first stage: In this stage, significant decrease of putrescine (Put) and spermidine (Spd), and disappearance of spermine (Spm) after mild water stress (40%FFC) indicated polyamine biosynthesis was obviously inhibited, resulting in a SAM (Sadenosylmethionine) accumulation and biosynthesis and release rate of ethylene increased subsequently. However, the ratio of ACC (1aminocyclopropane1carboxylic acid) and MACC (1(malonyamino)cyclopropane1carboxylic acid) was lower than 1 implying the malonyl transferase activity increased simultaneously with that of ACC synthase.The second stage: After subjected to severe drought (30%FFC), SAM biosynthesis was inhibited and the ratio of ACC/MACC exceeded 1. In the meantime polyamine biosynthesis greatly decreased and no Spd was detected. Leaf abscission occurred at this stage. Xylemfed ABA solution (10ml 200mM) caused similar changes of polyamine and ethylene as that of water stress. In parison with Italica , polyamine biosynthesis in Popularis leaves was less affected and Spd was detected after plants subjected to severe drought, and no leaf abscission was observed during the period of water stress. Ethylene release rate was less affected by drought and ACC/MACC never went beyond than 1. Therefore, ethylene biosynthesis in Popularis leaves was not significantly activated under water stress.Based on the genotypic differences in leaf abscission and in polyamine and ethylene biosynt
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