Blake T J, Filho W S
Faculty of Forestry, University of Toronto, Toronto, Ontario, Canada M6S 1A1.
Tree Physiol. 1988 Dec;4(4):325-35. doi: 10.1093/treephys/4.4.325.
To clarify the physiological basis of productivity differences among rooted cuttings and seedlings of eucalypt species, relationships between morphology and water relations were examined in 4-month-old seedlings of Eucalyptus grandis W. Hill ex Maiden, E. urophylla S.T. Blake and E. cloeziana F. Muell. and in 4-month-old rooted cuttings of three E. grandis cultivars. Four-month-old seedlings had greater dry weights, lower leaf area/root dry weight (LA/RDW) ratios and lower shoot/root dry weight (S/R) ratios than 4-month-old rooted cuttings. For all cultivars of E. grandis, tall rooted cuttings, as defined by height at age 4 weeks, had greater dry weights by age 4 months and lower LA/RDW and S/R ratios than short rooted cuttings. There were differences in height growth, dry matter productivity and relative shoot and root development among cuttings of different E. grandis cultivars, but these differences were not as great as the differences between short and tall grades of the same cultivar and between seedlings and cuttings. Consistent with the differences in LA/RDW and S/R ratios, seedlings had higher daytime water potentials (Psi(x)) than cuttings, and tall cuttings had higher daytime values of Psi(x) than short cuttings. Differences in Psi(x) were also related to stomatal conductance (g(wv)), which was up to 300% greater in short cuttings than in tall cuttings. Among seedlings, those of E. cloeziana, which had the smallest dry weight at age 4 months, had the highest g(wv), whereas those of E. grandis, which had the greatest dry weight at age 4 months, had the lowest g(wv). Unlike seedlings and the tall cuttings, short cuttings lost turgor when subjected to drought. The differences observed in susceptibility to water stress may account in part for the associated differences in dry matter production. Xylem pressure potential and relative water deficit at zero turgor did not differ significantly among the types of plants studied, which suggests that differences in growth rates were not the result of differences in dehydration tolerance.
为阐明桉树种扦插苗和实生苗生产力差异的生理基础，研究了巨桉（Eucalyptus grandis W. Hill ex Maiden）、尾叶桉（E. urophylla S.T. Blake）和粗皮桉（E. cloeziana F. Muell.）4月龄实生苗以及3个巨桉品种4月龄扦插苗的形态与水分关系之间的联系。4月龄实生苗比4月龄扦插苗具有更大的干重、更低的叶面积/根干重（LA/RDW）比和更低的地上部/根干重（S/R）比。对于所有巨桉品种，以4周龄时的高度定义的高扦插苗在4月龄时具有更大的干重以及更低的LA/RDW和S/R比，比矮扦插苗低。不同巨桉品种的扦插苗在高度生长、干物质生产力以及地上部和根的相对发育方面存在差异，但这些差异不如同一品种的矮级和高级扦插苗之间以及实生苗和扦插苗之间的差异大。与LA/RDW和S/R比的差异一致，实生苗的日间水势（Ψx）高于扦插苗，高扦插苗的日间Ψx值高于矮扦插苗。Ψx的差异也与气孔导度（gwv）有关，矮扦插苗的气孔导度比高扦插苗高300%。在实生苗中，4月龄时干重最小的粗皮桉实生苗具有最高的gwv，而4月龄时干重最大的巨桉实生苗具有最低的gwv。与实生苗和高扦插苗不同，矮扦插苗在干旱时会失去膨压。观察到的水分胁迫敏感性差异可能部分解释了干物质生产方面的相关差异。所研究的植物类型之间木质部压力势和零膨压时的相对水分亏缺没有显著差异，这表明生长速率的差异不是脱水耐受性差异的结果。
