Photosynthetic units of sun and shade plants.

A computer analysis of fluorescence induction curves of leaves treated with 3-(3,4-dichlorophenyl)-1,1 dimethylurea was done for several species. These measurements gave the ratios of the total chlorophyll to photosystem II reaction centers. This communication is a preliminary survey of sun and shade plants and demonstrates a significant variation in this ratio. In the sun plants, the photosynthetic unit sizes (chlorophyll reaction centers) varied between 220 to 480. The shade plants gave numbers mostly in the range between 630 to 940. The computer analysis of the fluorescence data also gave the connectivity parameter of energy transfer between photosynthetic units of photosystem II which varied between 0.2 and 0.5 but did not show any obvious correlation to the photosynthetic unit size.