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Impacts of Elevated CO2 on a Perennial Grass Species During Drought

Paper Reviewed
Xu, Q., Fan, N., Zhuang, L., Yu, J. and Huang, B. 2018. Enhanced stolon growth and metabolic adjustment in creeping bentgrass with elevated CO2 concentration. Environmental and Experimental Botany 155: 87-97.

In setting the stage for their study, Xu et al. (2018) write that "stolons are stems growing at the soil surface, with each stolon consisting of multiple nodes and internodes, and stolon nodes contain meristematic tissues capable of forming adventitious roots and daughter plants from the nodes." Furthermore, they note that stolons "are also storage organs for resources, such as carbohydrates, mineral nutrients and water, providing support for plant survival of environmental stresses." Consequently, stolon development and growth are, in their words, "highly desirable characteristics for stoloniferous plant species," including perennial grasses, which utilize stoloniferous propagation or sprigging for rapid stand establishment.

Unfortunately, Xu et al. note that limited information is available on the effects of elevated atmospheric CO2 concentration on stolon growth. Therefore, it was their objective to obtain such information on the perennial grass species known as creeping bentgrass (Agrostis stolonifera).

To accomplish this goal, the five scientists placed two-month-old samples of the grass species (cv. Alpha) in controlled-environment chambers under identical growing conditions. After a two-week acclimation period, the plants were subjected to treatments of either ambient (400 ppm) or elevated (800 ppm) CO2 and well-watered or deficit (50% of well-watered) irrigation conditions for the next 26 days. Multiple growth and physiological measurements were then made during the course of the treatment period.

In discussing their findings, Xu et al. report that drought caused a rapid decrease in plant relative water content (RWC) and increased leaf electrolyte leakage regardless of CO2 concentration. However, they found that elevated CO2 "alleviated the adverse effects of drought on both [of these] parameters in creeping bentgrass." In particular, at the end of the 26-day treatment period, plant RWC was 37.1% higher and leaf electrolyte leakage 44.5% lower in the drought treatment under elevated CO2 conditions compared to that observed in ambient CO2, while no significant differences between ambient or elevated CO2 were detected for these two parameters under well-watered conditions.

Xu et al. also report that elevated CO2 enhanced the growth of stolons, increasing "the number of stolon internodes by 25.8% and 75.6%, and the stolon length by 35.4% and 1.01-fold, respectively, under well-watered control and drought stress conditions." Furthermore, metabolic profiling revealed changes in several metabolites in the stolons in response to CO2 enrichment. In particular, metabolites involved with sugar metabolism, amino acid metabolism, fatty acid metabolism and respiratory metabolism in the stolon nodes were enhanced, leading the authors to reason that "the enhanced content of those metabolites could contribute to the stimulation of stolon growth by elevated CO2."

In commenting on these and other findings in their paper, Xu et al. say that "extensive stolon elongation is a highly desirable trait for the rapid establishment and survival from biotic and abiotic damages for stoloniferous grass species." And they add that "the CO2-responsive metabolites for carbohydrate reserves, respiratory metabolism, and membrane maintenance could contribute to the enhanced stolon growth, thereby potentially facilitating rapid stand establishment and increasing shoot biomass production in perennial grass species."

Consequently, the results of this study suggest that future increases in atmospheric CO2 concentrations will likely benefit this and other stoloniferous plant species, especially during times of drought.

Posted 14 January 2019