| 英文摘要 |
The senescence of excised primary leaves of Phaseolus vulgaris L. was followed by measuring the net breakdown of chlorophyll, protein, RNA, proteinase and ribonuclease activity. A decline of chlorophyll, protein, and RNA mark the progress of senescence in excised leaves. The chemical growth regulators, indoleacetic acid and gibberellic acid, were relatively ineffective in retarding senescence. Nβ-Benzyladenine at the concentration of 1×10^-5M was effective in retarding the decline in the amount of chlorophyll, protein and RNA. In the dark, L-serine at the concentration of 3×10^-2M promoted yellowing and RNA degradation of excised leaves. But in the light, it was ineffective in promoting senescence. Fluorescent light of 1,000 Lux, was very effective in senescence retardation. In the dark, adding sucrose (5.8×10^-2M) to the culture medium replaced the light function ln retarding the chlorophyll, protein and RNA loss. The senescence of excised leaves was retarded by cycloheximide (5 µg/ml.). It is assumed that, upon excision of leaves, the synthesis of some m-RNA responsible for the synthesis of destructive enzymes is activated, which ultimately leads to the breakdown of RNA and the protein synthesizing machinery. The protein inhibitors could then be expected to temporarily retard chlorophyll breakdown primarily by inhibiting the synthesis of destructive enzymes. The role of light and Nβ-Benzyladenine in the retardation of senescence may act synchronously. |
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