Stoneman G L, Turner N C, Dell B
Department of Conservation and Land Management, Research Center, P.O. Box 104, Como, WA 6152, Australia.
Tree Physiol. 1994 Jun;14(6):633-46. doi: 10.1093/treephys/14.6.633.
Leaf growth, rate of leaf photosynthesis and tissue water relations of shoots of Eucalyptus marginata Donn ex Sm. (jarrah) seedlings were studied during a soil drying and rewatering cycle in a greenhouse experiment. Rates of leaf growth and photosynthesis were sensitive to water deficits. The rate of leaf growth decreased linearly with predawn leaf water potential to reach zero at -1.5 MPa. Rate of leaf growth did not recover completely within the first three days after rewatering. Midday photosynthetic rates declined to 40% of those of well-watered seedlings at a predawn leaf water potential of -1.0 MPa and reached zero at -2.2 MPa. Photosynthetic rate recovered rapidly following rewatering and almost fully recovered by the second day after rewatering. All tissue water relations parameters, except the bulk modulus of elasticity, changed significantly as the soil dried and recovered completely by the third day after rewatering. Changes in osmotic pressure at full turgor of 0.4 MPa indicated considerable capacity for osmotic adjustment. However, because there was little osmotic adjustment until predawn leaf water potential fell below -1.5 MPa, this capacity would not have enhanced seedling growth, although it may have increased seedling survival. The sensitivity of photosynthesis and relative water content to water deficits suggests that greenhouse-grown E. marginata seedlings behave like mesophytic plants, even though E. marginata seedlings naturally grow in a drought-prone environment.
在温室实验的土壤干燥和复水周期中，研究了边缘桉（Eucalyptus marginata Donn ex Sm.，红柳桉）幼苗枝条的叶片生长、叶片光合速率和组织水分关系。叶片生长速率和光合速率对水分亏缺敏感。叶片生长速率随着黎明前叶水势呈线性下降，在-1.5MPa时降至零。复水后的头三天内，叶片生长速率并未完全恢复。黎明前叶水势为-1.0MPa时，午间光合速率降至水分充足幼苗的40%，在-2.2MPa时降至零。复水后光合速率迅速恢复，复水后第二天几乎完全恢复。随着土壤干燥，除弹性模量外的所有组织水分关系参数均发生显著变化，并在复水后第三天完全恢复。完全膨压下0.4MPa的渗透压变化表明有相当大的渗透调节能力。然而，由于直到黎明前叶水势降至-1.5MPa以下才有很少的渗透调节，这种能力虽然可能提高了幼苗的存活率，但不会促进幼苗生长。光合作用和相对含水量对水分亏缺的敏感性表明，即使边缘桉幼苗自然生长在易干旱的环境中，温室种植的边缘桉幼苗表现得像中生植物。
