Photosynthesis and Growth of Cotton (Gossypium hirsutum L.) Lines Deficient in Chlorophyll Accumulation

Abstract

Three virescent mutants and two wild-type lines of upland cotton were evaluated for chlorophyll (Chl), carotenoids (Car), carbon exchange ratio (CER), water use efficiency (WUE), chlorophyll fluorescence, and growth. Lines 30 and 174 were allelic for the virescent locus and had reduced ratios of Chl_Tot, Chl_a, Chl_b, CER, and WUE compared to DP90ne (in both 1995 and 1996). Line 174 had a higher CER than line 30 in both 1995 and 1996. The CER values of line 174 were similar to those of line 31. The only differences in fluorescent measurements were found in initial fluorescence (F₀) values, reflecting the concentrations of Chl. Of the three plant growth indicators, only plant height showed consistent statistical differences during growth. Reduced plant height was associated with lower chlorophyll concentrations. The number of main-stem nodes was slightly affected, with statistical differences occurring on only two dates—41 and 82 days after planting. The data indicate that these virescence alleles negatively influence most measurements of photosynthesis and cotton growth, but not all. Also, as previously reported in other crops, cotton leaf CER is not totally dependent on Chl_Tot levels.

Keywords:

• chlorophyll fluorescence
• CO₂ exchange rates
• cotton
• Gossypium hirsutum
• growth
• virescence

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