THE EFFECT OF LIGHT ON THE ELECTRICAL POLARITY AND THE RATE OF ELONGATION OF THE AVENA COLEOPTILE

Abstract

The data show that the apical half of a 30-mm. isolated Avena coleoptile sheath responds to uniform illumination from an incandescent lamp by changing its electrical polarity. After a delay of 20 min. the polarity decreased by 20 to 25 mv. and then returned to the original value. This period of decreasing electrical polarity was always accompanied by a decreased rate of elongation. These changes were produced either by continuous or short period illumination. In the intact coleoptile the period of decreased growth rate, which averages 19.6 minutes in length, was always followed by an elongation rate greater than the original rate. The apical half of the intact coleoptile was responsible for about 85% of the growth rate depression. The evidence presented indicates that the changes in bioelectric phenomena and the changes in rates of elongation are linked.