AbstractGrowth and qualitative effects of Polaris (N,N-bis [phosphono methyl]glycine) were evaluated in early-adult sugarcane receiving variable levels of solar radiation. Three experiments were performed in which plants initially propagated under clear glass received light, intermediate, and heavy shade regimes offering maximum light intensities of 5600, 2300, and 450 fc, respectively. Ripener treatments were given simultaneously in full sunlight (daily max.= 9600 fc). High sunlight intensities were not required for optimal Polaris action, and Polaris did not improve the plants' utilization of low light intensities. Growth repression under light- and intermediate-shade regimes was comparable to that attained under full sunlight. Maximum juice quality was produced under intermediate shade, while heavy shade eliminated entirely the ripener's qualitative effects. Results suggest that Polaris requires light at relatively low intensities for ripening processes not directly dependent upon photosynthesis, and that it can be used effectively under natural cloud cover restricting solar radiation levels to 2000-3000 fc.
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