PHOTOSYNTHESIS AND RESPIRATION IN RELATION TO LEAF AGE IN PERILLA FRUTESCENS (L.) BRITT

Abstract

SUMMARYThe rate of photosynthesis in the third pair of leaves of Perilla friitesceiis declined gradually from the time of completion of expansion of the leaves until approximately i week from abscission when there was a more rapid decrease. The decrease in rate of photosynthesis first became apparent in the parts of the lamina proximal to the petiole and gradually extended to the more distal regions. The rate of respiration of the leaf remained approximately constant until i week from abscission w hen there was a transient rise prior to tbe final decrease in rate, Tbe gradual decline in pbotosyntbesis was accompanied hy a similar decline in tbe RNA and protein content of tbe leaf altbough the cbloropbyll content did not cbange during tbis period, ^Measurements of pbotosyntbesis by means of' ''^CO, incorporation sbowed a similar pattern of cbange and further revealed that tbe rate of incorporation of label into protein declined more rapidly than did tbe total protein content, Tbe data are interpreted as suggesting tbe cessation of synthesis of proteins essential for pbotosyntbesis ratber tban an increased rate of proteolysis as tbe cause of tbe senescence cbanges.

APPARENT PHOTOSYNTHESIS AND LEAF CHARACTERS IN RELATION TO LEAF POSITION AND AGE, AMONG CONTRASTING LOLIUM GENOTYPES

“…Leopold, 1964;Hardwick, Wood and Woolhouse, 1968). In the present material it is clear that differences in age of up to 3 weeks between leaves were without effect on apparent photosynthesis.…”

Functional and Structural Changes in Senescing Populus deltoides (Bartr.) Chloroplasts

“…This decline in the rates of ATP synthesis was paralleled by the decline in the rate of C02 fixation. The results suggest that the efficiency of the membrane-bound ATP synthesizing system declines with age.Photosynthetic and respiratory rates vary with leaf age (8,13,14,22,23,26). In leaves of dicotyledon plants after an initial rise (3), the photosynthetic capacity gradually declines after leaf expansion (6,16,19,20 …”

Effects of Nitrogen Application on Dark-Respiration in Different Parts of Rice Seedlings

“…The reason why the Rs in the 2nd to 3rd (old) leaf blade was higher than that in the 4th to 6th (young) leaf blade is not clear. Hardwick et al (1968) observed the temporal increase of Rs in the senescent leaf blades at the final stage of aging. Amthor (1989) supposed that it was due to an increase in metabolic rate to support the energetic needs of remobilization of structural material.…”