Responses of four sweet potato cultivars to levels of shade: 1. Dry matter production, shoot morphology and leaf anatomy

Abstract

Total dry matter production of four sweet potato cultivars was not significantly affected by 25 or 55% shade but was severely reduced in 73% shade during the first eight weeks of growth. Overall mean relative growth rate was not lower in shade despite declining mean net assimilation rate because of high mean leaf area ratio increases, particularly in two of the four cvs. Leaf size increased as leaf number declined in response to the higher shade levels; thus, leaf areas were similar in all treatments. Leaf anatomy was modified in 73% shade with production of fewer mesophyll cell layers, especially in the two cvs. Petioles were shorter but branch length increased with increasing shade. The T1S 2328/6 cv appeared to be the most shade-tolerant cultivar in 55% shade; but no tolerance of 73% shade was found among the four sweet potato cultivars.