植物通过叶子表面微小的呼吸孔可以吸收二氧化碳进行光合作用，但是植物每吸收一分子的二氧化碳，植物自身都会从呼吸孔中蒸发掉大量的(约95%)水分子。如果环境中CO2的量很充足，那么水分的蒸发量将会下降，一直以来研究人员都不清楚其中的奥秘。
最近一项12月13日Nature Cell Biology杂志的研究报告，生物学家发现模式植物拟南芥(Arabidopsis)中存在着一类碳酸酐酶(carbonic anhydrases)，有助于植物在二氧化碳较高的环境中更有效地利用水分。
据Julian Schroeder介绍，许多植物对CO2的反应非常弱，因此，即使现在大气中的CO2水平要比工业革命以前高得多，并且CO2含量还在增加，植物也并未充分利用这些含量升高的CO2。
这项由Schroeder主持的课题组发现碳酸酐酶能够和CO2反应，从而使被打开的气孔附近的细胞关闭。碳酸酐酶能使CO2转变成为碳酸氢盐和质子。植物若是缺失碳酸酐酶相应的基因，那么即使空气中CO2的浓度上升，植物也不能有效的利用CO2。
虽然在多种植物细胞中都发现了碳酸酐酶，但该课题组表明，碳酸酐酶能够直接作用于能控制每一个呼吸孔开闭的保卫细胞(guard cells)。研究人员还发现，保卫细胞中如果导入多余的碳酸酐酶基因，将能使植物更有效的利用水分。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature Cell Biology 13 December 2009 | doi:10.1038/ncb2009
Carbonic anhydrases are upstream regulators of CO2-controlled stomatal movements in guard cells
Honghong Hu1,6, Aurélien Boisson-Dernier1,2,6, Maria Israelsson-Nordstr?m1,3,6, Maik B?hmer1,7, Shaowu Xue1,4,7, Amber Ries1, Jan Godoski1, Josef M. Kuhn1,5 & Julian I. Schroeder1
The continuing rise in atmospheric CO2 causes stomatal pores in leaves to close and thus globally affects CO2 influx into plants, water use efficiency and leaf heat stress1, 2, 3, 4. However, the CO2-binding proteins that control this response remain unknown. Moreover, which cell type responds to CO2, mesophyll or guard cells, and whether photosynthesis mediates this response are matters of debate5, 6, 7, 8. We demonstrate that Arabidopsis thaliana double-mutant plants in the β-carbonic anhydrases βCA1 and βCA4 show impaired CO2-regulation of stomatal movements and increased stomatal density, but retain functional abscisic-acid and blue-light responses. βCA-mediated CO2-triggered stomatal movements are not, in first-order, linked to whole leaf photosynthesis and can function in guard cells. Furthermore, guard cell βca-overexpressing plants exhibit instantaneous enhanced water use efficiency. Guard cell expression of mammalian αCAII complements the reduced sensitivity of ca1 ca4 plants, showing that carbonic anhydrase-mediated catalysis is an important mechanism for βCA-mediated CO2-induced stomatal closure and patch clamp analyses indicate that CO2/HCO3? transfers the signal to anion channel regulation. These findings, together with ht1-2 (ref. 9) epistasis analysis demonstrate that carbonic anhydrases function early in the CO2 signalling pathway, which controls gas-exchange between plants and the atmosphere.
