Three non-hybrid and two hybrid Bt cotton cultivars developed in Shandong province, as well as their control cultivar 33B, were grown and comparatively studied in 2002 and 2004. Results showed that three non-hybrid Bt cottons might be divided into an early-developed （ED） type （SCRC17 and SCRC21）and late-developed （LD） type （SCRC22）according to their earliness of maturity. In ED type, total biomass and leaf area per plant increased more quickly during early- and mid-season, and more slowly during late-season than those in the control. Plants of ED type exhibited enhanced earliness of maturity and even premature senescence in drought year. Contrasting to the ED type in accumulation of biomass and development of leaf area, LD type exhibited delayed earliness of maturity. Two hybrid cotton varieties （SCRC15 and SCRC 20） appeared similar to FD type in plant growth and development as well as earliness of maturity, but showed significantly higher increase in biomass and leaf area than all other varieties. No significant difference in net photosynthetic rate in functional leaves among genotypes before peak boll-setting stage, however, net photosynthetic rate in functional leaves of ED type was greatly inhibited relative to that of LD type at initial boll-opening stage, particularly in the drought year. Biomass ratio of root to the above ground, and K content in leaf blade in late-season were lower, but boll load per unit leaf area was higher, in FD type and hybrid cotton than in SD type. It is suggested that formance might be correlated to spectively. genotypic variation in accumulation of dry biomass and maturity perthe genotypic difference in leaf area and ratio of source to sink, respectively.
accumulation of biomass
source and sink