Effect of Light Quality on Growth and Free Indoleacetic Acid Content in Phaseolus vulgaris

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Abstract
A cycle of 8 hours light and 16 hours darkness was used to study the effect of light quality on elongation and "free" indoleacetic acid (IAA) content in P. vulgaris. After 1 light cycle the IAA content was estimated by an ultraviolet absorption method and confirmed by the 1st internode test. Plant heights were measured after 7 cycles. A direct relationship was found between the IAA content after 1 cycle and plant heights after 7 cycles. Plants grown in the dark (control) were the tallest and had the most IAA. Of the light treated plants those exposed to blue were the tallest and had the highest IAA content. Red light treatment produced plants which were shortest and had the least IAA. However, red light with a high proportion of farred increased both plant height and IAA content.