CO₂‐Enrichment Effects on Wheat Yield and Physiology¹

Abstract

High CO2 was applied to field‐grown winter wheat (Triticum aestivum L. cv. Arthur) during different growth periods in order to identify when photosynthesis was most limiting grain yield. Wheat was grown in open top Mylar® polyester chambers which were provided with circulated air (340 μL/L CO2 = control treatment) or air enriched with sufficient CO2 to expose the foliage to 1200 μL/L (high CO2 treatment). The CO2 enrichment treatments were applied from jointing to anthesis, from jointing to maturity, or from anthesis to maturity. Seed yield and total dry matter were influenced most by CO2 during the period from jointing to anthesis. The 17% increase in seed yield resulted from more seed per meter2, which was associated with an increase in heads per meter2. Total dry matter at maturity was increased by 11%. Neither harvest index nor nitrogen content of plant parts at harvest were altered by CO2 enrichment. In order to characterize the effect of CO2 on seed yield, several physiological parameters of leaf function were monitored using the flag leaves of plants grown in the control chambers and the high CO2 chambers treated from jointing to maturity. High CO2 had no significant effect on flag leaf chlorophyll and protein content or the onset of their decline during senescence. In addition, there was no effect on the level of ribulose bisphosphate carboxylase or its decline during senescence or on total proteolytic activity. High CO2 did, however, cause a 50% increase in apparent photosynthesis of the flag leaf. This resulted in a doubling of the sucrose and starch content of the flag leaf prior to seed growth. With the onset of seed growth this difference in sucrose and starch levels rapidly disappeared, suggesting a rapid mobilization to the head and developing seeds.

Significant Changes in Cell and Chloroplast Development in Young Wheat Leaves (Triticum aestivum cv Hereward) Grown in Elevated CO2

“…In older (4 week old) wheat plants we have found much larger starch deposits in tissue grown in elevated CO 2 (data not shown). These observations indicate that a shift in the source-sink status occurs in the older plant and leads to an accumulation of starch in the elevated CO 2 -grown leaf tissue as previously found in the other mature plants (Cave et al, 1981;Havelka et al, 1983;Vu et al, 1989;Yelle et al, 1989;Lawlor and Mitchell, 1991 …”

“…There have been several studies of the effects of elevated CO, on the growth of the wheat crop and its physiology (for reviews, see Lawlor and Mitchell, 1991;Long and Drake, 1992), and it is well established that increasing CO, levels can affect leaf growth and photosynthetic rates in wheat plants that are several weeks old (Akita and Moss, 1972;Neales and Nicholls, 1978;Havelka et al, 1983;du Cloux et al, 1989;Chaudhuri et al, 1990;Lawlor and Mitchell, 1991). Many of the effects on growth in elevated CO, may be secondary, since the initial response of the plant to elevated CO, is elicited immediately after atmospheric CO, is sensed by the plant.…”

Virus‐induced differences in the response of oat plants to elevated carbon dioxide

“…In wheat grown at [C02]7oo, foliar starch and sucrose were elevated in flag leaves until seed filling began; glucose levels were little altered (Havelka et al 1984). In A. sativa, we found that starch levels rose, dusk sucrose levels increased somewhat, and pre-dawn fructose fell with CO2 enrichment (Fig.…”

Accelerated Early Growth of Rice at Elevated CO2 (Is It Related to Developmental Changes in the Shoot Apex?)

“…It is possible that faster rates of cell division at high CO, are not only important during vegetative shoot initiation in the apex but also during grain initiation in the panicle and endosperm development in the grain. The importance of timing of exposure to elevated CO, in obtaining a yield increase at high CO, was also demonstrated by Havelka et al (1984) using wheat. When plants were exposed to high CO, during grain initiation, there was an increase in yield; however, there was no response to high CO, when plants were exposed to high CO, during grain filling only.…”