Photosynthetic carbon assimilation during development of leaves of Cestrum nocturnum and Setaria italica
1991
Thombre, R.R. (Institute of Science, Bombay (India). Dep. of Botany) | Karadge, B.A.
Changes in chlorophyll (Chl) content, rate of photosynthetic 14CO2 fixation (P), products of short term and steady state photosynthesis, photorespiratory rate and some related enzyme systems during the development of leaves of Cestrum nocturnum and Setaria italica were investigated. The amount of Chl increased in both plant species up to maturity and then declined towards senescence. The degradation of Chl a and b during senescence was accompanied by a decline in the Chl a:b ratio. The Hill reaction activity was higher in young leaves of Setaria than of Cestrum, higher in the mesophyll cells than in the bundle sheath cells of Setaria. The 3 s photosynthesis fixed more carbon into amino acids and organic acids than into sugars or sugar phosphates in both plant species. C3 cycle intermediates like 3-phosphoglycerate, glycine-serine, glycollate and sugar phosphates were dominant during the early photosynthetic period in Cestrum while malate was the initial photosynthate in Setaria showing its C4 nature. However, the C3 cycle was dominant over the C4 cycle during senescence in this species. The levels of photosynthetic and photorespiratory enzymes also differed according to both plant species and leaf age.
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