Effects of carbon dioxide enrichment at different irradiances on growth and yield of wheat triticum aestivum cultivar kleiber 2. effects on kleiber spring wheat treated from anthesis in controlled environments in relation to effects on photosynthesis and photorespiration

Kendall, A.C.; Turner, J.C.; Thomas, S.M.; Keys, A.J.

Journal of Experimental Botany 36(163): 261-273


ISSN/ISBN: 0022-0957
Accession: 005294040

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Spring wheat plants were grown in a cage with a glass roof until 3 days after anthesis and then subjected to treatments in constant environment rooms with any one of all combinations of 4 irradiances and 2 concentrations of CO2. The photoperiod was 16 h and day/night temperatures 19.degree. C/14.degree. C. Growth and yield of grain were saturated at the 2 brightest irradiances. CO2 enrichment from 350-1200 mm3 dm-3 increases shoot dry weight and grain yield at final harvest at all irradiances, by averages of 10.5 (not significant) and 23.5 (significant) percent, respectively. Increasing the irradiance from 150-613 .mu.E m-2 s-1 caused much larger yield increases (.apprx. 3-fold). Increased grain production by increased light was caused by both increases in dry weight per grain and by increases in grain number per spikelet. The increase caused by CO2 enrichment was mainly because of increased dry weight per grain. Increase in ear dry weight caused by CO2 enrichment took place between 30 and 60 days after anthesis. The increase in shoot dry weight took place immediately after exposure to increased CO2 from 3-15 days after anthesis. Net photosynthesis by flag leaves on the main shoots was almost doubled 16 days after anthesis by the CO2 enrichment even though stomatal resistance was also doubled. This increase was not reflected by a proportional increase in yield, probably because increased mutual shading by bigger stems and late litters reduced total assimilation and because of increased respiration by the shoots. The increase in photosynthesis was not due to a decrease in photorespiration but to an increase in gross photosynthesis.