The Effect of 2,4-Dichlorophenoxyacetic Acid on the Respiration of Etiolated Pea Seedlings.

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Abstract
The respiration rate of etiolated pea (Pisum sativum) seedlings declined rapidly after removal of the cotyledons. 2,4-Dichlorophenoxy-acetic acid (2,4-D) treated seedlings were able to maintain a higher rate of respiration during this period of decline then were untreated seedlings. Treatment consisted of placing the seedlings in the dark for 12 hrs. with their roots submerged in a buffered (pH 5.3) 10-3 [image] 2,4-D solution. The control and 2,4-D-treated seedlings were compared as to their RQ and as to their content of reducing sugar, starch, and sucrose. It was concluded that the higher rate of respiration exhibited by the 2,4-D-treated seedlings was not due to a greater amount of respiratory substrate being present. Respiratory data obtained from root tips of 2,4-D treated and untreated pea and corn (Zea mays) seedlings are presented and are compared with data from a previous report (Plant Physiol. 32: 136, 1957) concerning the effect of 2,4-D on pathways of glucose catabolism in root tips. It is postulated that 2,4-D increases respiration by causing more glucose to be catabolized via the pentose phosphate pathway.