Leaf water maintains daytime transpiration in young Cryptomeria japonica trees
Leaf water maintains daytime transpiration in young Cryptomeria japonica trees
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DOI：
10.1093/treephys/tpx056
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发表时间：
2017-10-01
期刊：
影响因子：
4
通讯作者：
Ishii, H. Roaki
中科院分区：
文献类型：
--
作者：
Himeno, Sawa;Azuma, Wakana;Ishii, H. Roaki
与茎贮水相比，叶贮水虽然对缓解水分胁迫有重要作用，但其对蒸腾需求的贡献迅速而直接。为了定量分析茎与叶贮水量对日水分亏缺的相对贡献，测定了10年生柳杉（Cryptomeria japonica D.）唐树。我们假设蒸腾速率与液流速度之间的时间滞后反映了茎和叶中的贮水量，茎体积的变化反映了弹性组织的含水量。全树的鲜质量和水势之间的关系表明，研究树木有能力存储，平均91.4毫升的水每公斤鲜质量在膨压损失。叶片、边材和弹性组织分别贡献了51%、29%和20%的贮水量。在上午，蒸腾速率高于树干液流速度，表明储存的水分消耗。在蒸腾开始后的第一个2小时，储存水的贡献超过100%的全树蒸腾。叶片水分（P-Leaf）和边材水分（P-Sap）的消耗与蒸腾作用的开始相一致，在15：00 h左右达到最大值。消耗的弹性组织水（P-弹性）落后于P-叶和P-SAP的1-2小时，表明储存的水的补充发生在当天晚些时候，低叶水势导致白天蒸腾驱动水分吸收。P-Leaf的最大消耗量分别约为P-Sap和P-Elastic的1-3倍和5-10倍。P-Leaf对日蒸腾量的贡献为5- 8%，P-Sap和P-Elastic分别为3-4%和0.7- 1%。我们的研究结果表明，在维持每日蒸腾作用在年轻的C。日本乔木
Compared with stem water storage, leaf water storage is understudied although it may be important for alleviating water stress by contributing quickly and directly to transpiration demand. To quantify the relative contribution of stem versus leaf water storage to daily water deficit, we measured diurnal changes in transpiration rate, sap-flow velocity and stem radius of 10-year-old Cryptomeria japonica D. Don trees. We assumed that the duration of time lags between transpiration rate and sap-flow velocity reflected stored water in the stem and leaf, and that stem volume change represented water content of elastic tissue. The relationship between fresh mass and water potential of the whole tree indicated that the study trees had capacity to store, on average, 91.4 ml of water per kg fresh mass at turgor loss. Leaves, sapwood and elastic tissue contributed around 51%, 29% and 20% of stored water, respectively. During morning, transpiration rates were higher than sap-flow velocity suggesting depletion of stored water. During the first 2 h after onset of transpiration, stored water contributed more than 100% of whole-tree transpiration. Depletion of leaf water (P-Leaf) and sapwood water (P-Sap) coincided with the onset of transpiration and became maximum around 15:00 h. Depletion of elastic tissue water (P-Elastic) lagged behind that of P-Leaf and P-Sap by 1-2 h, indicating that replenishment of stored water occurs late in the day when low leaf water potentials resulting from daytime transpiration drive water uptake. Maximum depletion of P-Leaf was about 1-3 times and 5-10 times that of P-Sap and P-Elastic, respectively. The contribution of P-Leaf to total daily transpiration was 5-8%, while those of P-Sap and P-Elastic were 3-4% and 0.7-1%, respectively. Our results suggest the importance of leaf water storage in maintaining daily transpiration in young C. japonica trees.