Dependence of the Stomatal Index on Environmental Factors during Stomatal Differentiation in Leaves of Vigna sinensis L.: 1. EFFECT OF LIGHT INTENSITY

The stomatal index of the trifoliate leaves of the Cowpea isa function not only of the total radiation received but alsoof variations in radiation during the 6 d preceding the majorphase of the unfolding of the leaf lamina. Hence, for sun plantsa whole day in the shade can cause a decrease in the stomatalindex provided this day occurs during the period defined above.For shade plants it is shown that a single day of high lightintensity during this critical period will cause an increasein the stomatal index. The latter is thus a characteristic foreach individual leaf. It is postulated that the site of photoperceptioncontrolling the stomatal index is located in the expanded adultleaves. Excision and transfer of still unfolding leaves to aculture medium partially prevents the influence of the olderexpanded leaves on the stomatal index of the excised leaf.