Photosynthetic and respiratory CO₂ exchange rates of source and sink organs of wheat and rice as influenced by panicle age

In the flag and penultimate leaves of wheat cv Sonalika and rice cv Ratna the photosynthetic rate was 2–4 times that of the respiratory rate: the decline in photosynthetic rate with age was more prominent in the flag leaf than that in the penultimate leaf. The respiratory rate was higher in the panicle at the later stages of panicle development. Photosynthetic rates were more adversely affected by panicle age than the respiratory rates in all the organs studied.