Sharkey Thomas D, Loreto Francesco
Department of Botany, University of Wisconsin, 53706-1383, Madison, WI, USA.
Oecologia. 1993 Sep;95(3):328-333. doi: 10.1007/BF00320984.
Kudzu (Pueraria lobata (Willd) Ohwi.) is a vine which forms large, monospecific stands in disturbed areas of the southeastern United States. Kudzu also emits isoprene, a hydrocarbon which can significantly affect atmospheric chemistry including reactions leading to tropospheric ozone. We have studied physiological aspects of isoprene emission from kudzu so the ecological consequences of isoprene emission can be better understood. We examined: (a) the development of isoprene emission as leaves developed, (b) the interaction between photon flux density and temperature effects on isoprene emission, (c) isoprene emission during and after water stress, and (d) the induction of isoprene emission from leaves grown at low temperature by water stress or elevated temperature. Isoprene emission under standard conditions of 1000 μmol photons·m·s and 30°C developed only after the leaf had reached full expansion, and was not complete until up to two weeks past the point of full expansion of the leaf. The effect of temperature on isoprene emission was much greater than found for other species, with a 10°C increase in temperature causing a eight-fold increase in the rate of isoprene emission. Isoprene emission from kudzu was stimulated by increases in photon flux density up to 3000 μmol photons·m·s. In contrast, photosynthesis of kudzu was saturated at less than 1000 μmol·m·s photon flux density and was reduced at high temperature, so that up to 20% of the carbon fixed in photosynthesis was reemitted as isoprene gas at 1000 μmol photons·m·s and 35°C. Withholding water caused photosynthesis to decline nearly to zero after several days but had a much smaller effect on isoprene emission. Following the relief of water stress, photosynthesis recovered to the prestress level but isoprene emission increased to about five times the prestress rate. At 1000 μmol photons·m·s and 35°C as much as 67% of the carbon fixed in photosynthesis was reemitted as isoprene eight days after water stress. Leaves grown at less than 20°C did not make isoprene until an inductive treatment was given. Inductive treatments included growth at 24°C, leaf temperature of 30°C for 5 h, or witholding water from plants. With the new information on temperature and water stress effects on isoprene emission, we speculate that isoprene emission may help plants cope with stressful conditions.
葛藤（Pueraria lobata (Willd) Ohwi.）是一种藤本植物，在美国东南部受干扰地区形成大片单一物种群落。葛藤还会释放异戊二烯，这种碳氢化合物会显著影响大气化学，包括导致对流层臭氧形成的反应。我们研究了葛藤异戊二烯排放的生理方面，以便更好地理解异戊二烯排放的生态后果。我们研究了：（a）随着叶片发育异戊二烯排放的变化；（b）光通量密度和温度对异戊二烯排放的相互作用；（c）水分胁迫期间及之后的异戊二烯排放；（d）水分胁迫或高温对低温下生长叶片异戊二烯排放的诱导作用。在1000 μmol光子·m²·s和30°C的标准条件下，异戊二烯排放仅在叶片完全展开后才开始，并且直到叶片完全展开后两周才达到稳定。温度对异戊二烯排放的影响比其他物种大得多，温度每升高10°C，异戊二烯排放速率就会增加八倍。光通量密度增加到3000 μmol光子·m²·s时，葛藤的异戊二烯排放会受到刺激。相比之下，葛藤的光合作用在光通量密度小于1000 μmol·m²·s时就达到饱和，并且在高温下会降低，因此在1000 μmol光子·m²·s和35°C时，光合作用固定的碳中高达20%会以异戊二烯气体的形式重新释放。停止浇水几天后，光合作用几乎降至零，但对异戊二烯排放的影响要小得多。水分胁迫解除后，光合作用恢复到胁迫前的水平，但异戊二烯排放增加到胁迫前速率的约五倍。在1000 μmol光子·m²·s和35°C下，水分胁迫八天后，光合作用固定的碳中高达67%会以异戊二烯的形式重新释放。在低于20°C的温度下生长的叶片，在进行诱导处理之前不会产生异戊二烯。诱导处理包括在温度24°C下生长、叶片温度30°C持续5小时或对植株停止浇水。根据关于温度和水分胁迫对异戊二烯排放影响的新信息，我们推测异戊二烯排放可能有助于植物应对胁迫条件。
