Effects of Elevated and Decreased CO₂ Concentration in a Part of Leaves of Phaseolus vulgaris L. on Photosynthesis.

Abstract

Photosynthesis of a leaf is regulated not only by own light environment, but also the light environment of the whole plant (Weaver et al. 2001). Thus, plants would have some mechanisms, which recognize and compare the environments among the leaves. To examine effects of environments around a part of leaves on photosynthesis in themselves and the other leaves in a plant, we treated a couple of primary leaves of bean with 1000, 400 and 150 ppm CO₂ concentration. After treatments, we measured changes in photosynthesis of the primary leaves (PL) and the first trifoliate (FT).
The photosynthetic rate at 360 ppm CO₂ of 1000 ppm-treated PL and FT decreased faster than that of 400 ppm during the treatment period, and 150 ppm-treated PL decreased slower. Thus, CO₂ environment around PL affects the photosynthetic rate of PL and FT.