
%0 Journal Article
%A Pan, Q. 
%A Wang, Z. 
%A Quebedeaux, B. 
%T Responses of the apple plant to CO<sub>2</sub> enrichment: changes in photosynthesis, sorbitol, other soluble sugars, and starch
%J Functional Plant Biology
%D 1998/05/21
%V 25
%N 3
%P 293-297
%K 
%R https://doi.org/10.1071/PP97097
%U https://www.publish.csiro.au/paper/PP97097 
%X There is no information on the effects of elevated &#91;CO2&#93; on whole-plant photosynthesis and carbohydrate metabolism in apple (Malus domestica Borkh.) and other sorbitol-translocating plants. Experiments were conducted in controlled growth chambers to evaluate how increases in &#91;CO2&#93; affect plant photosynthesis and carbon partitioning into soluble sugars and starch in apple leaves. Apple plants (cv. Gala), 1-year-old, were exposed to &#91;CO2&#93; of 200, 360, 700, 1000, and 1600 &#181;L L-1 up to 8 d. Whole-plant net photosynthetic rates were analysed daily after &#91;CO2&#93; treatments. Newly expanded mature leaves were sampled at 1, 2, 4, and 8 d after &#91;CO2&#93; treatments for sorbitol, sucrose, glucose, fructose, and starch analysis. Midday whole-plant net photosynthetic rates increased linearly with increasing &#91;CO2&#93;, but the differences in whole-plant photosynthesis between CO2-enrichment and ambient &#91;CO2&#93; treatments were less significant as apple plants acclimated to high atmospheric &#91;CO2&#93; for 8 d. Increases in &#91;CO2&#93; significantly increased sorbitol and starch, but did not affect sucrose concentrations. As a result, the ratios of starch to sorbitol and starch to sucrose at 8 d after &#91;CO2&#93; treatments were increased from 0.05 and 0.06 to 0.8 and 1.6 as &#91;CO2&#93; increased from ambient &#91;CO2&#93; (360 &#181;L L-1) to 1000 &#181;L L-1 &#91;CO2&#93;, respectively. The sorbitol to sucrose ratio also increased from 1.3 to 2.2 as &#91;CO2&#93; increased from 360 to 1000 &#181;L L-1. Elevated &#91;CO2&#93; enhanced the photosynthesis of apple plants and altered carbohydrate accumulation in mature leaves in favour of starch and sorbitol over sucrose. 
