Growth of some variants of tobacco plants, known to be deficient in chlorophyll, was comparable to that of normal green variants. Three variants of
Nicotiana tabacum (“Bright Yellow”) “Burley 21” and Shirogiri”., as well as
N. sylvestris, were examined with respect to the relationship between chlorophyll content and photosynthetic CO
2 uptake. In three of the four materials examined we found that the photosynthetic CO
2 uptake was in proportion to the chlorophyll content. “Burley 21”. containing 1/2 to 1/10 of the amount of chlorophyll of normal plants of the same age, grew as well as “Bright Yellow” (normal green). For young and old leaves of a normal green variant, CO
2 uptake was saturated at about 20, 000lux, whereas with old leaves of a virescent variant, the rate of CO
2 uptake was still increasing at 40, 000lux. At this intensity old and young leaves of both variants showed similar rates of CO
2 uptake per unit leaf area, but on a chlorophyll basis the leaves of the virescent were two to twenty times more active than those of the normal.
Photochemical reaction measurements on chloroplasts also showed that the activity of chloroplasts from old leaves of the virescent was the highest of all.
The rates of photosynthetic CO
2 uptake of young leaves of both variants continued to rise with temperature, but that of old leaves of the virescent variant was rather low at higher temperature.
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