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 s ativum L. variety JI 141 were measured at various stages of senescence . These optical properties were correlated with the percentage water c ontent 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 fin al stages of pod desiccation were also investigated using scanning ele ctron microscopy. The significance of these results are discussed in r elation to the use of optical properties to monitor pod moisture conte nt and the photoenvironment of the senescing pod as it affects 1) phyt ochrome levels before final seed desiccation and 2) near UV light tran smission to the drying seed.