Decline in photosynthesis as related to alterations in chloroplast ultrastructure of a cotton leaf during ontogeny
1998
Bondada, B.R. (University of Tennessee, Knoxville (USA). Dept. of Plant & Soil Science) | Oosterhuis, D.M.
Field studies were conducted to investigate ontogenic changes in leaf photosynthesis and chloroplast ultrastructure of a single cotton (Gossypium hirsutum) leaf subtending the fruit. A 20-d old leaf was the most physiologically active with net photosynthetic rate (PN) of 16.5 micromol m** (-2) s** (-1) and nitrogen (N) concentration of 168 mmol m** (-2). These values declined with leaf age and a close relationship existed between them. Concurrent with declines in PN, ultrastructural alterations occurred in the chloroplast: the 20-d old leaf had increased grana number and thylakoids per granum and a few plastoglobuli. The PN was closely related to grana number and thylakoids per granum suggesting that the decline in PN with leaf age was associated with ultrastructural changes in the chloroplast.
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