Effect of Pre-Illumination on the Response of Split Pea Stems to Growth Substances

Abstract

Light had a marked effect on the response of the seedlings in the pea test for growth-regulating activity of chemicals. Split stems from seedlings grown in complete darkness gave little or no response to solns. of growth substances, but pre-illumination secured a response. Time of exposure and amt. and quality of the light proved critical in obtaining maximal response. Red light was most effective; single exposures should be started 32 hrs. prior to harvesting the pea stems. At an intensity of 10 foot-candles, a 4-hr. exposure to red light resulted in the greatest curvature in the pea test. A pre-harvest exposure of the seedlings to red light greatly increased the curvature in the pea test and eliminated occasional batches which otherwise would not respond to growth substances.