Estimation of ultraviolet radiation as a limiting factor for vertical distribution of plants by studying their ultraviolet resistance.

1）。在生长箱中生长的亚洲车前幼苗，只有来自亚高山带的植物在紫外线照射后，其UV-B辐射吸收物质的含量发生了显著变化。在所有的植物中，只有在强紫外线照射后才能检测到这些物质中的车前草素，而在弱紫外线照射和强紫外线照射后都能检测到一种未鉴定的物质。紫外线照射后，不同海拔的植物叶绿素荧光特性存在差异.虎杖的叶绿素荧光光谱显示其抗紫外线水平极高。但是，海拔高度和抗紫外线水平之间似乎没有关系。--随着生境海拔的升高，日本Trautvetteriajaponica的生物量逐渐增加。在5种低山地带的禾本科植物中，分布在海拔最高处的虎杖抗紫外线能力最强。

1). Young Plantago asiatica grown in a growthcabinet.Only the plants derived from upper subalpine zone remarkably varied the amount of UV-B radiation absorbing substances after UV irradiation. Plantaginin among the substances was detected in all the plants only after a strong UV irradiation, and an unidentified substance after both a weak and strong UV irradiation. Some charactors of chlorophyll fluorescence after UV irradiation differed between the plants from low and high altitudes.2). Native species ill the field.UV resistance level of Polygonum cuspidatum shown as chlorophyll fluorescence was remarkably high. But, there seemed to be no relation between altitude and levels of UV resistance. --That of Trautvetteria japonica, however, becalae higher with the increase of its habitat's altitude. On 5 species of grasses growing in lower montane zone, UV resistance was the highest in P. cuspidatum, which distributes into the highest altitudes among these species.