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Abstract

Continuing increases in atmospheric carbon dioxide concentration, [CO 2 ], will likely be accompanied by global warming. Thus, it is important to quantify and understand the consequences of elevated [CO 2 ] and temperature on crop growth and yield to develop suitable varieties and agronomic management practices for future climates. The objective of this study was to investigate the growth and development responses of shoots and roots of peanut (Arachis hypogaea L.) grown under different combinations of atmospheric [CO 2 ] and temperature. The study comprised a long-term experiment, in which plants were grown in growth chambers for 112 days, and a short-term experiment, in which growing plants in rhizotrons for 17 days. In the long-term experiment, peanut cultivar Tainan 9 was grown in 20-L containers fitted with minirhizotron observation tubes at 5 cm soil depth and placed in controlled environment chambers under three levels of [CO 2 ] (400, 600, and 800 µmol mol -1 ) and two levels of air temperature (25/15ºC and 35/25ºC day/night temperature). In the short-term experiment, two peanut seedlings were grown in each of 18 acrylic rhizotrons with a 6-mm thick soil layer. Rhizotrons with plants were placed in the same growth chambers as above. At 3-to 4-day intervals, rhizotrons were placed on a flatbed scanner to collect digital images from which root length and number were measured using RMS software. At 25/15ºC, plants grown at 600 and 800 µmol mol -1 CO 2 had main stems that were 24 and 44% longer than those grown at 400 µmol mol -1 , while at 35/25ºC the main stem length was similar in all [CO 2 ] levels. At 25/15ºC, plants showed greater area and dry weight per leaf than at 35/25ºC. At harvest, high temperature significantly reduced total leaf area to 574 cm 2 for 35/ 25ºC compared with 921.2 cm 2 for 25/15ºC. Specific leaf area at low temperature was 22% less than at high temperature. Above ground biomass was increased by elevated CO 2 in both temperature treatments. At high temperature, above ground biomass was 56%, 24%, and 16% higher than at low temperature at [CO 2 ] of 400, 600 and 800 µmol mol -1 , respectively. Pod dry weight increased with increasing [CO 2 ] at 25/15ºC, but was not different among [CO 2 ] levels at 35/25ºC. At 25/15ºC, pod dry weight was 50% higher than at 35/ 25ºC. As the temperature increased from 25/15ºC to 35/25ºC, pod dry weight was reduced by 40% at 400, 53% at 600, and 54% at 800 µmol mol -1 CO 2 . High temperature produced more root length in the containers, whereas low temperature did in the rhizotrons. There were significant interactions between temperature and [CO 2 ] for their effects on main stem length and above ground biomass. High temperature enhanced growth of shoots and roots, but decreased pod dry weight. There was no interaction of elevated [CO 2 ] with higher temperature on the reproductive growth, despite a tendency for beneficial temperature by [CO 2 ] interaction on vegetative growth and total shoot dry weight. The beneficial effects of increased ...

Dynamics of Plant Root Growth under Increased Atmospheric Carbon Dioxide

“…Temperature and CO 2 effects were studied in groundnut and total root length increased with increasing CO 2 from 400 to 800 μmol mol -1 at both low and high temperatures (Pilumwong et al, 2007). Although the difference was not significant, there was an observed increase of 13% when plants were grown at 600 μmol mol -1 CO 2 , and 20% at 800 μmol mol -1 CO 2 .…”

“…In maize (Zea mays L.) grown under elevated CO 2 relative growth rate of maize roots was increased compared to the relative shoot growth rate (Whipps, 1985) because of increased C translocation to the roots. Pilumwong et al (2007) reported increased root growth of groundnut due to increasing CO 2 concentration. With no limitations to water and nutrients, elevated CO 2 increased root and shoot growth of most plant species including tree species (Obrist and Arnone, 2003;Rogers et al, 1996;Pregitzer et al,1995) but the response varied among species (Hanley et al, 2004).…”

“…Observations from a spring wheat FACE study revealed a 37% increase in total root dry mass in the CO 2 -enriched plot during early vegetative growth (stem elongation) and sustained root growth rates until anthesis . The combined effect of temperature and elevated CO 2 concentration affect growth and development of roots, Pilumwong et al (2007) observed in groundnut (Arachis hypogaea L.) that fibrous root dry weight increased with increased CO 2 when plants were grown at 25/15°C, but decreased with increasing CO 2 at 35/25°C. At 35/25°C, there was greater root dry weight by 34% at 400, 14% at 600, and 7% at 800 μmol mol -1 compared with 25/15°C.…”

“…This hypothesis is supported from observations by Berntson and Bazzaz (1995), demonstrating the potential of root systems to acquire resources may increase because of greater total root length densities; however, there may be a decline in the efficiency of resource capture. Root systems of crops grown in CO 2enriched environments are often more branched, especially at shallower soil depths, compared to roots of crops grown in ambient air (sorghum, Chaudhuri et al, 1986;wheat, Chaudhuri et al, 1990;Fitter et al, 1996;Caratonia siliqua, Cruz et al, 1997;soybean, Del Castillo et al, 1989;cotton, Rogers et al, 1992;Pilumwong et al, 2007;Senecio vulgaris, Berntson and Woodward, 1992). These observations indicate altered belowground plant function suggesting higher level soil ecological processes may change as atmospheric CO 2 continue to increase (Pritchard and Rogers, 2000;Rogers et al, 1997Rogers et al, , 1999.…”

Effects of elevated CO2 concentration on bulbil germination and early seedling growth in Chinese yam under different air temperatures

“…According to the results of the Tukey-Kramer's test, vigour index I and vigour index II exhibited the same trend in Enshikei 6; that is, both vigour indexes had significantly have reported that elevated [CO 2 ] stimulates the growth of both shoots and roots (Conn & Cochran, 2006;Pilumwong et al, 2007;Usuda & Shimogawara, 1998;Ziska et al, 1997). However, the allocation of biomass to shoots and roots in crops under elevated [CO 2 ] may be different from that under ambient [CO 2 ] under certain conditions.…”