Effects of Growth-Regulatory Chemicals on the Action Spectra for 14C Assimilation and Transport in Sugarcane Leaves

Abstract

Pretreatment of sugarcane with the growth hormone gibberellic acid (GA₃) and the growth depressant Polaris [N,N-bis (phosphonomethyl) glycine] significantly altered the action spectra for ¹⁴C assimilation and transport by leaf tissues. Leaf segments enclosed in a ¹⁴CO₂ atmosphere were illuminated with discrete wavelengths of equal quantum flux from 400 to 710 nanometers (nm). Both compounds significantly lowered ¹⁴C assimilation in the blue, from 437 to 480 nm. Polaris accentuated a green depression at 550 nm while lowering assimilation peaks in the red at 600-640 nm and at 670 nm. Translocation of ¹⁴C, as percentages of the total nuclide assimilated, was vastly increased by both materials in the blue-violet (400 nm) and by GA₃ in the blue (437-480 nm). Polaris increased transport from the blue-green to yellow (520-600 nm). A high sensitivity of control plants to far-red light (710 nm) was unaffected by either material. These results support the theory that chemical ripening may involve sugar synthesis and transport processes in addition to growth-regulatory effects in sink tissues.