Leaf area, shoot dry weight, specific leaf weight and plant height all increased, but enrichment gave growth increases only up to the visible bud stage. Similarly, while sunflowers gain increased stem thickness, enrichment was not beneficial at the flowering stage although it significantly increased the number of buds on each plant.
The physiological evidence strongly indicates that most plants have the potential for increased production rates, but the extent of plant response is also dependent upon factors such as temperature, light and nutrition, as well as the level Of C02 in the atmosphere.
Blackman's Law states that the rate of any process which is governed by two or more factors is limited by the factor in least supply. The process of photosynthesis is a classic example of this rule. For example, on an overcast day it is pointless raising the temperature more than 5°C above the night temperature in a controlled greenhouse environment because the low light intensity will limit the rate of photosynthesis. Any additional heat will be without benefit. Conversely, if it is a bright sunny day and the temperature is not raised, then lack of heat may become the limiting factor for photosynthesis.
The physiological
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Thanate Tan
