PHOTOSYNTHESIS, RESPIRATION AND WATER-CONTENT IN BRYOPHYTES
PHOTOSYNTHESIS, RESPIRATION AND WATER-CONTENT IN BRYOPHYTES
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DOI：
10.1111/j.1469-8137.1979.tb07564.x
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发表时间：
1979-01-01
期刊：
影响因子：
9.4
通讯作者：
PROCTOR, MCF
中科院分区：
文献类型：
--
作者：
DILKS, TJK;PROCTOR, MCF
干旱生境（如：Tortula intermedia、Camptothecium lutescens）表现出最适，在高水分含量下光合作用再次下降。水分胁迫可刺激呼吸，但不受高含水量的影响。在低含水量下，光合作用和呼吸作用曲线的陡峭部分处于类似的范围内。一些物种经常潮湿的栖息地（例如，Pellia epiphylla、Hookeria lucens）显示光合作用逐渐增加至500-1000%干重的含水量，并且随着植物变干，在比呼吸低得多的水分亏缺下受到影响。光合作用和呼吸作用对水势的响应在两组中大致相似。在所研究的物种中，在-60至-100巴下通常存在可测量的光合作用，但在-150至-200巴下很少或没有光合作用。呼吸作用继续使水势有所降低，但其限度尚未确定。对5个树种的嫩枝含水量进行了田间测定。在12个月的时间内。在T. muralis比在林地物种。田间最大含水量一般位于光合响应曲线的最优值附近。较低的水含量记录在这些和在公布的数据被认为是在有关的吸附等温线的brutites和其他植物材料。与芽有关的水分可分为（1）细胞壁内的水（质外体水），（2）细胞质内的水（共质体水）和（3）外部毛细管水。低于约-200巴的含水量变化主要发生在（1）内，在-200巴和-2巴之间的含水量变化主要发生在（2）内，在较高的水势下的含水量变化主要发生在（3）内。水在芽中的运动在生理上是重要的;水的分布和运动由细胞壁和植物表面的毛细空间的几何形状介导。在具有乳突状叶的物种中，乳突之间的间隙中的毛细血管传导率足以平衡蒸发。细胞壁内的传导可能是重要的，在物种与非乳突叶，但其他途径也可能参与，在这些物种的水分运动需要进一步调查。
Response curves of photosynthesis to water content of bryophytes of dry habitats (e.g., Tortula intermedia, Camptothecium lutescens) show an optimum, with photosynthesis declining again at high water contents. Respiration may be stimulated by water stress, but is unaffected by high water contents. The steep portions of the photosynthesis and respiration curves lie within a similar range at low water contents. Some species of constantly moist habitats (e.g., Pellia epiphylla, Hookeria lucens) show photosynthesis increasing progressively to water contents of 500-1000% dry weight, and affected at much lower water deficits than respiration as the plant dries out. The response of photosynthesis and respiration to water potential is broadly similar in the 2 groups. In the species investigated there was generally measurable photosynthesis at -60 to -100 bar, but little or none at -150 to -200 bar. Respiration continues to somewhat lower water potentials of which the limits were not determined. Field measurements of the water content of shoots of 5 spp. over a period of 12 mo. showed much greater variation in T. muralis than in the woodland species. Maximum water contents in the field generally lay close to the optima of the photosynthesis response curves. The lower water contents recorded in these and in published data are considered in relation to sorption isotherms for bryophytes and other plant materials. The water associated with bryophyte shoots can be divided into (1) water within the cell walls (apoplast water), (2) water within the cytoplasm (symplast water) and (3) external capillary water. Changes in water content below about -200 bar take place chiefly within (1), between -200 and -2 bar within (2), and at higher water potentials chiefly within (3). Water movement within the shoots is physiologically important; the distribution and movement of water are mediated by the geometry of the capillary spaces of the cell walls and the plant surface. In species with papillose leaves, rates of capillary conduction in the interstices between the papillae are more than sufficient to balance evaporation. Conduction within the cell walls is likely to be important in species with non-papillose leaves, but other pathways may also be involved, and water movement in these species requires further investigation.