Liakoura V., Manetas Y., Karabourniotis G.
Laboratory of Plant Physiology, Agricultural University of Athens, Iera Odos 75, G-11855 Botanikos, Athens, Greece; Laboratory of Plant Physiology, University of Patras, G-26500 Patras, Greece.
Physiol Plant. 2001 Apr;111(4):491-500. doi: 10.1034/j.1399-3054.2001.1110409.x.
Leaves of 14 representative Mediterranean plant species were collected on a monthly basis and assayed for UV-absorbing compounds concentration, either on an area or a dry mass basis, from 1995 to 1997. Strong seasonal fluctuations were observed in eight species (all evergreens, two phrygana, one deciduous, one summer perennial and one winter perennial). Two different patterns of changing concentrations of UV-absorbing compounds were observed. In the first, concentration of these compounds was higher in young developing leaves and concentration declined during maturation, whereas in other plants, the opposite trend was observed. These differences could be attributed to the particular leaf surface morphology of each plant. The observed seasonal fluctuations of UV-absorbing compounds seem to be more correlated to developmental processes, than to seasonal fluctuations of the naturally occurring UV-B radiation. Most of the winter perennials did not show strong fluctuations during the period of development. The concentration of these compounds varied not only on a seasonal basis among the examined plants, but between different life forms as well: during winter, examination of the leaves of 13 species showed that evergreen sclerophylls and phrygana had at least two-fold higher concentration of UV-B-absorbing compounds on a leaf area basis than winter perennials. In addition, during the same season and irrespective of life form and species, the absorbance at 300 nm per unit of mature leaf area followed an asymptotic exponential decrease when specific leaf area increased. The UV-B radiation screening capacity of the leaves of these plants is discussed in relation to each adaptive strategy.
1995年至1997年期间，每月采集14种具有代表性的地中海植物的叶片，测定其紫外线吸收化合物的浓度，以面积或干重为基础。在8种植物（均为常绿植物，2种为地中海常绿矮灌丛植物，1种为落叶植物，1种为夏季多年生植物和1种为冬季多年生植物）中观察到强烈的季节性波动。观察到紫外线吸收化合物浓度变化的两种不同模式。第一种模式是，这些化合物在幼嫩的发育叶片中浓度较高，在成熟过程中浓度下降，而在其他植物中则观察到相反的趋势。这些差异可能归因于每种植物特定的叶片表面形态。观察到的紫外线吸收化合物的季节性波动似乎与发育过程的相关性更大，而不是与自然发生的UV-B辐射的季节性波动相关。大多数冬季多年生植物在发育期间没有表现出强烈的波动。这些化合物的浓度不仅在所研究的植物之间随季节变化，而且在不同的生活型之间也有所不同：在冬季，对13种植物的叶片进行检查发现，常绿硬叶植物和地中海常绿矮灌丛植物在叶面积基础上的UV-B吸收化合物浓度至少是冬季多年生植物的两倍。此外，在同一季节，无论生活型和物种如何，当比叶面积增加时，每单位成熟叶面积在300nm处的吸光度呈渐近指数下降。结合每种适应策略讨论了这些植物叶片的UV-B辐射屏蔽能力。
