No abstract
Elevated carbon dioxide throughout the lifespan of soybean causes an increase in photosynthesis, biomass, and seed yield. A rectangular hyperbola model predicts a 32% increase in soybean seed yield with a doubling of carbon dioxide from 315 to 630 ppm and shows that yields may have increased by 13% from about 1800 A.D. to the present due to global carbon dioxide increases. Several other sets of data indicate that photosynthetic and growth response to rising carbon dioxide of many species, including woody plants, is similar to that of soybean. Calculations suggest that enough carbon could be sequestered annually from increased photosynthesis and biomass production due to the rise in atmospheric carbon dioxide from 315 ppm in 1958 to about 345 ppm in 1986 to reduce the impact of deforestation in the tropics on the putative current flux of carbon from the biosphere to the atmosphere.
Global atmospheric C0 2 concentration ([C0 2 )) is increasing as a result of the burning of fossil fuels. At present there is little information about how agronomic crops will respond to future high [C0 2 [. To investigate the basic process that will be most affected, soybean (Glycine max (L.) Merr.[ canopies were continuously exposed to various [C0 2 [ and photosynthetic rates were measured throughout the growing season. Soybean was grown to physiological maturity in sunlit controlled-environment chambers in C0 2 concentrations of 330, 450, 600, and 800 ~L L -I. Carbon dioxide fluxes were measured on the canopies at 15-min intervals every day and used to calculate photosynthetic and respiration rates. Gross photosynthetic rate increased with each increment in [C0 2 [ regardless of stage of development, but there was considerable day-to-day and seasonal variation. Seasonal changes in photosynthetic rate were associated with developmental changes in the crop. Photosynthetic rates were low during early vegetative development, even after the canopy had closed, but increased threefold just before flowering to reach a peak during flowering at stage R2. They then decreased by 30% or more until just before the start of pod expansion (R3) when a 45% increase occurred. Thereafter, photosynthetic rates decreased slowly and continuously to final harvest. The daily curves of photosynthetic rate vs. photosynthetic photon flux density were further analyzed to determine canopy light utilization efficiency (a) and canopy conductance to C0 2 transfer (T). Plants grown in 800 ~L L -I [C0 2 ) had a value of a that averaged about 40% higher than that for plants grown in 330 ~L L -I and a value ofT that averaged about 24% lower for the season. Differences in a between these treatments were significant throughout the season, while initial differences in T between treatments became less obvious after late vegetative growth stage Vll.Additio1111l index words: Glycine max (L.) Merr., Light utilization efficiency, Conductance to C0 2 transfer.
Cotton (Gossypium hirsutum L.) produces excessive vegetative growth when grown under optimum water and nutrient conditions. The plant growth regulator Mepiquat Chloride (MC); 1,l‐dimethyl piperidinium chloride reduces vegetative growth and can promote early maturity. Its effect on yield has been inconsistent, with some researchers showing an increase while others have indicated a decrease. This variation in yield has often been attributed to environmental factors and variations in water and fertilizer inputs. This study examined the effect of MC on cotton growth, under varying irrigation treatments, to determine if soil moisture interacts with MC. The experiment was conducted in 1987 with two cotton cultivars, Stoneville 825 (‘ST825’) and Deltapine 20 (‘DP20’), grown in pots, with five irrigation treatments [1.2,1.0,0.8,0.6, and 0.4 times previous day's pan evaporation (PE)] each with and without MC applied. Mepiquat Chloride reduced plant height, number of main stem nodes, and internodal length. The effect on boll numbers was mixed between cultivars. In some instances under the same irrigation treatment (1.2 PE), the number of bolls was higher in ST825 with MC applied than with control while in DP20 the control treatment had the higher number of bolls. Mepiquat chloride's effectiveness on vegetative growth tended to decrease as the number of days after application increased. Differences in response within irrigation treatments was attributable to MC. Differences in response between irrigation treatments with MC applied was attributable to irrigation and cultivar differences and not to interaction between soil moisture and MC.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.