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EFFECTS OF ULTRAVIOLET‐B IRRADIANCES ON SOYBEAN. IV. LEAF ONTOGENY AS A FACTOR IN EVALUATING ULTRAVIOLET‐B IRRADIANCE EFFECTS ON NET PHOTOSYNTHESIS
Author(s) -
Teramura Alan H.,
Caldwell Martyn M.
Publication year - 1981
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1981.tb07809.x
Subject(s) - biology , photosynthesis , ontogeny , irradiance , botany , photosynthetic capacity , ultraviolet , sunlight , ultraviolet radiation , chemistry , physics , quantum mechanics , astronomy , radiochemistry , genetics
There has recently been concern that some anthropogenic atmospheric pollutants, such as chlorofluoromethanes, may result in a global reduction in stratospheric ozone. This would undoubtedly increase the level of ultraviolet radiation reaching the surface of the earth. Such an increase in solar ultraviolet irradiation might have important biological consequences. Unifoliate leaves of decapitated soybean plants were exposed to 0, 20, 50, and 90 effective mW m 2 UV‐B BE (weighted ultraviolet‐B irradiance) from special lamps in a greenhouse. The effects of UV‐B radiation were examined in leaves at three different ontogenetic stages: bud; one‐third expanded, and fully expanded leaves. Leaf area expansion, net photosynthesis, specific leaf weight, chlorophyll concentrations, and acidified methanol extract absorbance were measured during the course of the study. These data revealed several generalizations concerning the relationship between leaf ontogeny and photosynthetic response to UV‐B radiation: 1) The rate and duration of leaf expansion are affected by low levels of UV‐B irradiation. 2) There appears to be a shift in the ontogenetic sequence of photosynthetic capacity as a function of leaf age. 3) This results in leaves of similar chronological ages being in different physiological stages of maturity.