|Gowda, Madhu -|
Submitted to: Agronomy Journal
Publication Type: Review Article
Publication Acceptance Date: December 20, 2012
Publication Date: April 1, 2013
Citation: Gowda, M.M., Hatfield, J.L. 2013. Dynamics of plant root growth under increased atmospheric CO2. Agronomy Journal. 105:657-669. Interpretive Summary: Increasing carbon dioxide in the atmosphere affects plant growth, and most of the information available has evaluated the effects on the above ground portion of the plant. These summaries have shown that there is a positive effect on vegetative growth; however, there has been no summary of the effects on increasing carbon dioxide on root growth and development. There is information available from different studies but these have not been summarized to help provide a synthesis of information to help guide our understanding of how root growth may response to the increased levels of carbon dioxide expected in the coming decades. This information will be of value to scientists to help guide further research on plant responses to climate change.
Technical Abstract: Plant growth is influenced by above and below ground environmental conditions and increases in atmospheric CO2 concentration enhances growth and yield of most agricultural crops. Roots of plants greatly influence plant growth and its productivity which is an important agronomic parameter from point view of soil and input management. This review covers current knowledge on the impact of increasing CO2 concentration on root dynamics of plants in term of growth, root:shoot ratio, root biomass, root length, root longevity, root mortality, root distribution, root branching, root quality and the response of these root parameters to management practices including soil water and nutrients. Roots of crop plants are stimulated to a greater extent than any other plant parts. Many studies reported photosynthesis and carbon allocation to plant roots increases as atmospheric CO2 rises thereby increase above and below biomass with few exceptional results. The results on the effects of CO2 concentration on root: shoot ratio are contradictory due to complexity in accurate underground biomass estimation under diverse crops and conditions. Roots become more numerous, longer, thicker, and faster growing in crops exposed to high CO2 with increased root length in many plant species. Increased root growth of plants contributes to root biomass and root dry weight has increased under elevated atmospheric CO2 in most studies regardless of species or study conditions. Branching and extension of roots under elevated CO2 may lead to altered root architecture and ability of roots to acquire water and nutrients from the soil profile with exploration soil volume. Root lifespan has important consequences for plant growth and productivity, and also influencing carbon and nutrient fluxes within terrestrial ecosystems. Longevity of roots is controlled by a roots position within the soil profile and other resource availability in the soil. Very few studies have focused on this aspect and needs more long-term studies with varied resource availability may generate better knowledge of root lifespan to understand current theories regarding plant adaptation and growth strategies. Numerous studies have shown that elevated CO2 may result in increased root biomass in agronomic crops. Greater growth rates, root diameter, root volume, and root area also have reported in higher CO2 levels and very few studies have addressed CO2 induced changes in root quality /thickness/diameter and structure suggesting further studies especially under field environments. Root turnover is important to the global carbon budget as well as to nutrient cycling in ecosystems and to the success of individual plants. Agricultural management practices have a greater impact on root growth than rising atmospheric CO2 since management practices influence soil physical, chemical and biological properties of soil, consequently affects root growth dynamics in the belowground. Less understood are the interactive effects of elevated CO2 and management practices including drought on root dynamics, fine-root production and water-nutrient use efficiency, and the contribution of these processes to plant growth in water and nutrients limited environments. Increases in water-use efficiency and reductions in water use may contribute to enhanced soil water content under elevated CO2.