Seasonal variations in water relations in current-year leaves of evergreen trees with delayed greening
Seasonal variations in water relations in current-year leaves of evergreen trees with delayed greening
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DOI：
10.1093/treephys/26.8.1025
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发表时间：
2006-08-01
期刊：
影响因子：
4
通讯作者：
Yamamoto, Shin-Ichi
中科院分区：
文献类型：
--
作者：
Harayama, Hisanori;Ikeda, Takefumi;Yamamoto, Shin-Ichi
研究了三种常绿阔叶树(冬青、女贞)当年叶水分关系的季节变化规律。和Eurya Japan onica Thunb.)日本暖温带森林的绿化延迟。我们使用压力-体积法来：(1)评估叶片水分关系的季节变化在多大程度上归因于延迟绿叶的叶片发育过程与环境变量的季节性变化；(2)调查从幼树到成树阶段过渡过程中叶片水分关系的变化。单位叶面积的叶质量一般在5月份(晚春)叶展开完成后最低，全年逐渐增加。在所有树种中，盛水期渗透势(Psi(Ft)(O))和失水点叶水势(Psi(TLP)(W))在5月份最高，在隆冬时最低。随着气温的下降，Psi(Ft)(O)以0.037兆帕摄氏度-1的速度下降。各树种的叶片干物质含水率和共生体含水率在全年叶片总含水率中逐渐降低。这些结果表明，叶片发育过程中共生体含水率的减少导致细胞内溶质的被动浓度，从而导致冬季Psi(Ft)(O)的下降。越冬期大叶和大叶的溶质/水量比增加，说明渗透调节(溶质的主动积累)也是导致T ft冬季下降的原因之一。细胞壁的体积弹性模数有季节性波动，但没有发现跨物种的总体趋势。在整个生长季节，成树的Psi(Ft)(O)和Psi(TLP)(W)均低于幼树，尤其是马尾松，说明成树的叶片比幼树更耐干旱和耐寒。花梗L个体发育抗逆性的增强可能与其特有的生活型有关，因为其生长高度高于所研究的其他物种。
We investigated seasonal patterns of water relations in current-year leaves of three evergreen broad-leaved trees (Ilex pedunculosa Miq., Ligustrum japonicum Thunb. and Eurya japonica Thunb.) with delayed greening in a warm-temperate forest in Japan. We used the pressure-volume method to: (1) assess the extent to which seasonal variation in leaf water relations is attributable to leaf development processes in delayed greening leaves versus seasonal variation in environmental variables; and (2) investigate variation in leaf water relations during the transition from the sapling to the adult tree stage. Leaf mass per unit leaf area was generally lowest just after completion of leaf expansion in May (late spring), and increased gradually throughout the year. Osmotic potential at full turgor (Psi(ft)(o)) and leaf water potential at the turgor loss point (Psi(tlp)(w)) were highest in May, and lowest in midwinter in all species. In response to decreasing air temperature, Psi(ft)(o) dropped at the rate of 0.037 MPa degrees C-1. Dry-mass-based water content of leaves and the symplastic water fraction of total leaf water content gradually decreased throughout the year in all species. These results indicate that reductions in the symplastic water fraction during leaf development contributed to the passive concentration of solutes in cells and the resulting drop in winter Psi(ft)(o). The ratio of solutes to water volume increased in winter in current-year leaves of L. japoniculn and E. japonica, indicating that osmotic adjustment (active accumulation of solutes) also contributed to the drop in winter in T ft. Bulk modulus of elasticity in cell walls fluctuated seasonally, but no general trend was found across species. Over the growing season, Psi(ft)(o) and Psi(tlp)(w) were lower in adult trees than in saplings especially in the case of I.pedunculosa, suggesting that adult-tree leaves are more drought and cold tolerant than sapling leaves. The ontogenetic increase in the stress resistance of L pedunculosa may be related to its characteristic life form because I. pedunculosa grows taller than the other species studied.