1、F1 太阳辐射与植物要 点辐射能和光合作用绿色植物能够利用的惟一能源是辐射能。当叶子截获辐射能时，它能被吸收、反射或者透射。吸收的部分能量到达叶绿体，引发了光合作用，在这个过程中，辐射能被用于转化水和二氧化碳成为糖。太阳辐射包含了不同波长的光谱。然而，仅有一个有限的光谱带对光合作用是有效的。这就是光合活性辐射（ PAR）带，对绿化植物是位于 380nm到 700nm之间。F1 SOLAR RADIATION AND PLANTSRadiant energy is the sole energy source that can be used by green plants. When a le
2、af intercepts radiant energy it may be absorbed, reflected or transmitted. Part of the fraction absorbed reaches the chloroplast, fuelling photosynthesis, the process where radiant energy is used to convert water and CO2 into sugars. Solar radiation contains a spectrum of different wavelengths. Howe
3、ver, only a restricted band of this spectrum is effective for photosynthesis. This is the band of photosynthetically active radiation (PAR) and for green plants lies between 380 and 710 nm.Key NotesRadiant energy and photosynthesis辐射能转换效率计算光合作用效率是有可能的。作为生物化学过程，光合作用是高效率的；进入反应部位的可用辐射能的35%转化为潜在能量。在植物水平
4、上的真实效率在0.5%和 3%之间变化，取决于植物和环境。C3和 C4植物 植物光合能力中的主要差别是在 C3和 C4植物之间。 C4植物能捕获 CO2 ， 伴随着水的利用效率比 C3植物更大，而这优点需要消耗能量。在 C4植物中，光合作用率随光强度而增加，而 C3植物随光强度增加光合作用渐渐减小。c4植物的叶片结构 It is possible to calculate the efficiency of photosynthesis. As a biochemical process photosynthesis is efficient; 35% of usable4 radiant e
5、nergy entering a reaction site is converted to potential energy. The actual efficiency at the plant level varies between 0.5% and 3.0%, depending on the plant and the environment.Efficiency of radiant energy conversionA major difference in the photosynthetic capacity of plants is that between C3and
6、C4 plants. C4 plants are able to capture CO2 with greater water use efficiency than C3 plants, but this advantage comes at an energy cost. In C4 plants the rate of photosynthesis increases with light intensity, whilst photosynthesis tails off with increasing light intensity in C3 plants. C3 and C4 p
7、lants辐射强度的变化植物很难获得它们完全的光合作用潜能，是由于水短缺和辐射强度的改变。光强度的系统变化是太阳辐射的日节律和年节律。光强度中极少部分的系统变化是因叶子彼此的相对位置引起。植物对辐射的战略和战术响应植物种间对辐射强度反应的主要战略差异显示为 “阳地种 ”和 “阴地种 ”，它们分别具有适应于高的和低的光辐射范围。同样，植物能够在不同光条件下生长不同的叶子，作为对光环境的部分战术反应。这一点最清楚地在单株植物叶冠内的阳叶和阴叶的结构上看到。Plants rarely achieve their full photosynthetic potential, due to water
8、shortage and to variation in the intensity of radiation. The systematic variations in light intensity are the diurnal and annual rhythms of solar radiation. Less systematic variations in light intensity are caused by the positioning of leaves in relation to each other.Changes in the intensity of rad
9、iationA major strategic difference between plant species in their response to the intensity of radiation is exhibited by sun species and shade species, which possess a range of adaptations to high and low light levels, respectively, Also, plants may grow leaves which develop differently under differ
10、ent light conditions as part of a tactical response to the light environment. This is most clearly seen in the formation of sun leaves and shade leaves within a leaf canopy of single plant.Strategic and tactical response of plants to radiation光合作用的控制气孔是为光合作用而吸收 CQ2的通路。然而，如果气孔张开，允许 CQ2进入叶内，水通过蒸发将离开叶子。在大多数陆地生态系统中，至少在一段时间内，当水的供应短缺时，光合作用控制的某些形式必定启用。植物对这种困境具有大量的对策回应。
