OPTICAL-PROPERTIES OF THE POD WALL OF THE PEA (PISUM-SATIVUM L) .3. THE EFFECTS OF SENESCENCE AND POD DESICCATION

The transmission, reflection and absorption spectra of pods of Pisum sativum L. variety JI 141 were measured at various stages of senescence. These optical properties were correlated with the percentage water content and levels of chlorophyll a, b and total chlorophyll of the pod wall at each stage. Photomorphogenic effects of pod senescence on the seed environment were deduced from changes in the ratio of 660/730 nm light transmitted through the pod wall. Structural aspects of the final stages of pod desiccation were also investigated using scanning electron microscopy. The significance of these results are discussed in relation to the use of optical properties to monitor pod moisture content and the photoenvironment of the senescing pod as it affects 1) phytochrome levels before final seed desiccation and 2) near UV light transmission to the drying seed.