THE RESPIRATION OF GROWING PLANT CELLS

Abstract

The rate of the respiration of growing cells of the hypocotyl was studied in sunflower seedlings. The cells occurred in different phases of growth from the embryonic to the inature in the 7 zones chosen. The respiration was detd. With a micro-respirometer. Averages of 20 separate tests were listed. A method was devised to express the rate of respiration per unit mass of protoplasm in arbitrary units. The rate declines with time in all zones. The highest rate of respiration occurs in the embryonic cells, where nucleo- and cytoplasm are greatest per cell volume. It is interpreted to mean that young protoplasm respires more than old protoplasm. The av rate of respiration declines from the youngest zones to the oldest except in the 3d zone where cell enlargement is maximum. The high rate of respiration in the 3d zone suggests that the metabolic activity in this zone is stimulated by auxin.