Post-pollination biochemical changes in the floral organs of Rhynchostylis retusa (L.) Bl. and Aerides multiflora Roxb. (Orchidaceae)

摘要

If left unpollinated, the flowers of Aerides multiflora (Roxb.) and Rhynchostylis retusa (L.) Bl. can remain fresh for 17 and 24 cl, respectively. However, they begin to wilt at 2 to 3 days after pollination (DAP) and 3 to 4 DAP, respectively, and become senescent at 5 DAP and 7 DAP, respectively. When measured at two developmental phases -- Stage 1, start of wilting and Stage 2, progression to senescence -- all the floral organs from pollinated flowers had higher contents of total soluble sugars, reducing sugars, and free amino acids than those from unpollinated flowers. A corresponding increase was noted in the activities of hydrolytic enzymes, i.e., alpha-amylase, beta-amylase, and invertase, and proteolytic enzymes (proteases) in those organs. This indicated that signals related to pollination had up-regulated those activities, leading to a breakdown of complex molecules into simpler ones for mobilization. The amounts of sugars and enzyme activity were relatively greater in the pollinated flowers of A. multiflora compared with R. retusa, and levels were always higher in the floral lips and perianths. When inhibitors of auxin (0.25 mM TIBA) or ethylene (0.25 mM AgNO3) were applied to the pollinated flowers, their senescence was partially prevented, thus signifying hormonal involvement in governing the pollination-induced biochemical alterations normally found in those organs.