卡內(nèi)基學(xué)院全球生態(tài)系和德國(guó)尤里希研究中心的科學(xué)家一項(xiàng)最新的合作研究顛覆了傳統(tǒng)的關(guān)于蒸騰作用過(guò)程中氣孔結(jié)構(gòu)調(diào)節(jié)葉片水蒸氣流失的觀念,。研究人員發(fā)現(xiàn)輻射是葉子內(nèi)部物理過(guò)程的驅(qū)動(dòng)力,。
這項(xiàng)研究中關(guān)于植物氣孔的一些深入認(rèn)識(shí)將會(huì)對(duì)天氣預(yù)測(cè)，環(huán)境變化,，農(nóng)業(yè),，水文地理等產(chǎn)生巨大的影響,。該研究結(jié)果發(fā)布在2010年7月12日Proceedings of the National Academy of Sciences雜志的在線版本上。
氣孔能夠調(diào)節(jié)光合作用所需的二氧化碳流入，以及蒸騰作用中的水蒸氣外流,。蒸騰作用使我們的大氣環(huán)境保持清爽和濕潤(rùn),，調(diào)節(jié)環(huán)境，同時(shí)增加降雨,。氣孔影響植物從大氣中吸收二氧化碳的比率,，從而影響植物的生產(chǎn)率，以及大氣中二氧化碳的濃度,。因此，理解氣孔對(duì)于研究氣候變化來(lái)說(shuō)是很重要的,。
目前科學(xué)家使用的用于氣孔反應(yīng)描述的環(huán)境變化模型是基于統(tǒng)計(jì)分析的,。這種方法不是基于對(duì)氣孔調(diào)節(jié)機(jī)制的理解，因此不能很好的推斷環(huán)境因素,?？茖W(xué)家對(duì)植物氣孔的研究已經(jīng)有300多年了，但是令人驚奇的是,，關(guān)于氣孔的調(diào)控機(jī)制還沒(méi)有很好的理解,。這項(xiàng)研究的共同作者Joseph Berry表示。
更多閱讀進(jìn)入生物谷 www.bioon.net
在這項(xiàng)研究中,，科研人員首次考察了能量以及葉子外表面水蒸氣的交換機(jī)制,，結(jié)果發(fā)現(xiàn)這與葉子內(nèi)部的過(guò)程相關(guān)，色素從輻射中吸收的能量以及葉子內(nèi)部的水分含量影響了氣孔調(diào)控水分的程度,。
研究人員以向日葵葉子作為觀察對(duì)象,，并使用強(qiáng)光照射（含有或?yàn)V過(guò)近紅外光）。Berry觀察到,，當(dāng)近紅外光沒(méi)有被過(guò)濾時(shí),，氣孔會(huì)打開(kāi)，間接刺激光合作用,。在相同能量輸入的情況下,，不同顏色的光照，氣孔打開(kāi)程度相似,。此外,，更多的證據(jù)表明熱是驅(qū)動(dòng)因素。在相同的條件下,，科學(xué)家使用其他5種植物進(jìn)行了重復(fù)試驗(yàn),。同時(shí)，他們還開(kāi)發(fā)了一個(gè)基于能量平衡的葉子系統(tǒng)模型,。模型的試驗(yàn)結(jié)果和實(shí)驗(yàn)室結(jié)果相似的,。
根據(jù)試驗(yàn)和模型結(jié)果，研究人員推測(cè)，由植物保衛(wèi)細(xì)胞形成的氣孔具有精確的敏感性和信息處理系統(tǒng),，它們利用光和環(huán)境中的其他信號(hào)調(diào)整氣孔,。這項(xiàng)研究的突破點(diǎn)則是首次證實(shí)了氣孔水分流失率的調(diào)控與葉子的內(nèi)部物理過(guò)程有關(guān)。(生物谷Bioon.net)
生物谷推薦原文出處：
PNAS doi: 10.1073/pnas.0913177107
Control of transpiration by radiation
Roland Pieruschkaa,b, Gregor Hubera, and Joseph A. Berryb,1
aForschungszentrum Jülich GmbH, Institut für Chemie und Dynamik der Geosph?re, 52425 Jülich, Germany; and
bCarnegie Institution of Washington, Department of Global Ecology, Stanford, CA 94305
The terrestrial hydrological cycle is strongly influenced by transpiration—water loss through the stomatal pores of leaves. In this report we present studies showing that the energy content of radiation absorbed by the leaf influences stomatal control of transpiration. This observation is at odds with current concepts of how stomata sense and control transpiration, and we suggest an alternative model. Specifically, we argue that the steady-state water potential of the epidermis in the intact leaf is controlled by the difference between the radiation-controlled rate of water vapor production in the leaf interior and the rate of transpiration. Any difference between these two potentially large fluxes is made up by evaporation from (or condensation on) the epidermis, causing its water potential to pivot around this balance point. Previous work established that stomata in isolated epidermal strips respond by opening with increasing (and closing with decreasing) water potential. Thus, stomatal conductance and transpiration rate should increase when there is condensation on (and decrease when there is evaporation from) the epidermis, thus tending to maintain homeostasis of epidermal water potential. We use a model to show that such a mechanism would have control properties similar to those observed with leaves. This hypothesis provides a plausible explanation for the regulation of leaf and canopy transpiration by the radiation load and provides a unique framework for studies of the regulation of stomatal conductance by CO2 and other factors.
