OPTICAL-PROPERTIES OF THE POD WALL OF THE PEA (PISUM-SATIVUM L) .1. GENERAL-ASPECTS

The %transmission, reflection and absorption of the carpel wall of Pisum sativum L. has been compared with other pea tissues: leaf, testa and cotyledon. Although considerable overall differences were found, especially in the levels of light that were transmitted, there were qualitative similarities which correlated with the presence of chlorophyll in all the tissues. Reasonably high maximum light fluxes were found within the green pod and testa of Pisum sativum L. exposed to sunlight but these would be considerably lower under canopy conditions. The presence or absence of wax on the pod surface did not affect transmission, reflection or absorption spectra significantly. The sclerenchyma layer made a significant contribution to pod reflection, and to the absorption of potentially harmful near-UV radiation, while the inner layer of cells had a high absorption of red and blue wavelengths consistent with chlorophyll absorption. The chlorophyll concentrations were found to be highest in the inner layer and cotyledon tissues, but still much lower than those in leaves. The Red/Far-Red ratio decreased as light penetrated the pod and testa, so that the photomorphogenic environment of the embryo had a much lower R/FR ratio than that of daylight. This may have implications for seed development. The optical properties of pods are discussed in relation to their photosynthetic function and possible photomorphogenic consequences for the developing seeds within the modified light regime of the pod. © 1990, Gustav Fischer Verlag, Stuttgart. All rights reserved.