DISTRIBUTION OF PROTEIN-STORING CELLS IN THE BARK TISSUE OF HEVEA BRASILIENSIS IN RESPONSE TO TAPPING PANEL DRYNESS AND STIMULATION

摘要

Latex from Hevea brasiliensis is harvested through controlled wounding (tapping) of the latex vessels present in the bark tissue. The continuous injury on the bark leads to regeneration of the tissue involving various anatomical and biochemical changes in the cells adjacent to the wounded bark. In general, trees of high yielding Hevea clones when subjected to over-harvesting latex are susceptible to tapping panel dryness (TPD), resulting into the cessation of latex flow. The actual mechanism involved in the partial or complete cessation of latex flow in the TPD affected trees is still obscure. The distribution and occurrence of protein-storing cells (PSC) in the secondary phloem (bark) are a common phenomenon which is considered as an end product of various translocation mechanisms taking place in the bark tissue. In healthy trees of rubber, the PSC was distributed in one or two layers surrounding the phloic rays and also adjacent to sieve tubes, where as its density was increased in TPD affected trees (4-5 layers) as well as in TPD affected regions of stimulated trees. The PSC were in close association with the sieve elements which were an important in the movement of photosynthates. Occurrence, structure and distribution of PSC and its functional role in Hevea bark tissue with respect to TPD and stimulation were studied and discussed.