Response of Sugar-Cane Cuttings to Auxin Treatment as Modified by Other Applied Compounds

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Abstract
The response of cuttings of 2 vars. of sugar cane, C. P. (Canal Point) 36/105 and C.P. 36/13, to auxin treatments as modified by other applied compounds was studied. The use of sucrose or KMnO4 singly did not significantly benefit germination, shoot growth, or rooting, whereas combined use of indoleacetic acid (IAA) with sucrose and of the amine salt of alpha-ortho-chlorophenoxypropionic acid (a-O-CPA) with KMnO4 significantly increased germination and root weight and volume. A combination of IAA and a-O-CPA (91) stimulated rooting more than did IAA used singly. When this treatment was followed by nitrogen additions to the rooting medium, a still further significant stimulation was observed. Thiamin chloride added to the rooting medium had little effect. Sucrose combined with the auxin-nitrogen treatment effected a significant decrease in all rooting responses. Cuttings made from the upper stalk were found to be responsive to added sucrose and those from the basal stalk to applied auxin; this suggests the necessity of a suitable auxin-sugar balance for optimum response. Cuttings from the middle stalk evidently had the most favorable balance for optimum normal response. Pre-exposure of cuttings to ethylene was antagonistic to subsequent auxin treatment in terms of rooting, although germination and shoot response were not significantly affected. Treatment of cuttings with auxins resulted in a decrease of reducing sugars and sucrose 24 hours after treatment. Reducing sugars decreased and sucrose increased from top to bottom of the stalk. The rate of respiration, as measured by CO2 evolution, was accelerated by auxin treatment. Respiration was highest in the top portion of the stalk, and it decreased with distance from the stalk apex. The possible mechanism of action and the interaction of the various factors studied are discussed.