ANALYSIS OF ELONGATION AND THICKENING OF INTERNODES IN SWEET SORGHUM (SORGHUM-BICOLOR MOENCH)

An early-maturing cultivar Sucrosorgo 301 (S301) and a late-maturing c ultivar Sucrosorgo 405 (S405) were grown in low population (LP : 100 c m between rows, 50cm within rows) and high population (HP : 50cm betwe en rows, 20cm within rows). At the early stage, plant length was longe r in HP than in LP, though at harvest time it was longer in LP. The lo west 'elongated internode (greater than or equal to 1cm)' of S301 was the 6th internode (IN6) and that of S405 was IN7. In both cultivars, a nd elongated internode at the lower part of stem was longer in HP than in LP, while that at upper part was shorter in HP than in LP. The int ernode diameter was consistently larger in LP than in HP. To analyze t he internode growth pattern, the position of a fully-expanded leaf on the stem was used for counting plant age (AL) : for instance, the plan t age for just expanded 10th leaf (L10) was defined as AL10. A concept ional growth curve of internode elongation was drawn based on IN9 simi lar to IN12 elongation pattern. IN (n) (n : natural number) rapidly el ongated at AL (n+2) and reached its maximum size at AL (n+3)similar to AL (n+4). Plant density affected the rate of internode elongation. Th e internode thickening pattern was expressed by two different growth c urves. Thickening of IN (n) was not affected by the plant density unti l AL (n). INn reached a maximum diameter at AL (n+5) in LP and at AL ( N+2) in HP. So the diameter of IN (n) in LP was larger.