The most extreme case is illustrated by the out of control orientation o of OTV in LEO where irradiances of 56 W/m for short periods (1 or 2 seconds) can be obtained. Even this most extreme case will not affect either photosynthesis or plant development. Plants do not exhibit sensitivity to direct insolation. Indeed most plants characterized as ''sun- plants'' (plants which grow in conditions of direct exposure to sunlight as opposed to ''shade-plants” which grow in shaded environments, e.g., forest floors) orient their leaves perpendicular to the sun's rays to maximize interception of sunlight. Ground irradiance from OTV in LEO would not be expected to affect those plant parts oriented toward sunlight since the increase in irradiance would only amount to 4$ of full sunlight. There is no evidence to suggest that even very large changes in irradiance affect plants (by comparison with effects on the human eye). Rather, over a wide range of irradiances, the rate of photosynthesis would change and saturation would occur at 20# of full sunlight (Fig. 1). Above saturation there is no evidence suggesting deleterious effects of full sunlight on the photosynthetic process. Similarly, during full sunlight there is no evidence that the development of sun-plants would be affected by irradiation from OTV in LEO. In full sunlight phytochrome levels will have reached a photostationary state (3,^) and indeed the photostationary state would be saturated by a fraction of the energy of full sunlight. The development of plants exposed to sunlight will reflect the fact that phytochrome is predominantly (greater than 60^) in the PFR form. Since all developmental responses to red-light are known to be saturated when PFR exceeds 50^ of total phytochrome, small deviations from maximum full sunlight can have no affect on developmental responses controlled by phytochrome.
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