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Relationship of Photosynthetic Rate to Growth and Fruiting of Cotton, Soybean, Sorghum, and Sunflower 1
Author(s) -
Mauney J. R.,
Fry K. E.,
Guinn G.
Publication year - 1978
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1978.0011183x001800020016x
Subject(s) - sunflower , sorghum , helianthus annuus , biology , agronomy , lint , horticulture , zoology
Cotton ( Gossypium hirsutum L.), sorghum ( Sorghum bicolor L.), soybean ( Glycine max L.), and sunflower ( Helianthus annuus L.) plants were exposed during daylight hours to an atmosphere enriched with CO 2 to 630 ppm (v:v) (HiCO 2 ) in a glasshouse. Temperature was trolled continuously to produce a daily maximum of 35 C and a minimum of 21 C. Days were cloudless and long, May to August, in Phoenix, Ariz. Average CO 2 exchange rate (CER) increased 15% for cotton, 2% for sorghum, 41% for soybean, and 7% for sunflower compared to the CER of these species at 330 ppm CO 2 (LoCO 2 ). The increase in CER was not statistically significant for sorghum and sunflower. Measurements of relative growth rateRGR ¯and net assimilation rateNAR ¯showed the growth rate of all species increased during the juvenile stage (10d‐30d) in the enriched atmosphere.RGR ¯andNAR ¯were not higher in the enriched atmosphere after the juvenile stage, but cotton and soybean plants maintained their larger size and greater absolute growth. Final dry weights of cotton and soybean increased 110 and 380%, respectively, in HiCO 2 compared to LoCO 2 . Lint yield of cotton was increased 180% by HiCO 2 on a per‐plant basis and 88% on a unit leaf area basis. Became of growth fimitations imposed by terminal flowers, the final size of sorghum and sunflower plants in HiCO 2 was not significantly larger than in LoCO 2 These results imply that selection for CER will not effectively increase yield of determinate species such as sunflower and sorghum, but may effectively increase yield of indeterminate species such as cotton and soybean, if a sensitive assay for CER can be found.