Young Cucumbers Sprayed with Brassinosteroids and Growing in CO2-Enriched Air
Jiang, Y.-P., Cheng, F., Zhou, Y.-H., Xia, X.-J., Shi, K. and Yu, J.-Q. 2012. Interactive effects of CO2 enrichment and brassinosteroid on CO2 assimilation and photosynthetic electron transport in Cucumis sativus. Environmental and Experimental Botany 75: 98-106.
Against this backdrop and working with well-watered and fertilized plants that had reached the three-leaf growth stage in pots containing a 6:3:1 (by volume) mixture of peat, vermiculite and perlite that were located within controlled environment growth chambers maintained at either ambient (380 ppm) or enriched (760 ppm) atmospheric CO2 concentrations, and with or without being sprayed with a solution of brassinosteroids (0.1 µM 24-epibrassinolide), Jiang et al. measured - among several other things -- rates of net photosynthesis, leaf area development and shoot biomass production over a period of one additional week.
The six scientists determined that their doubling of the air's CO2 concentration resulted in a 44.1% increase in CO2 assimilation rate; and they write that the BR treatment "also significantly increased CO2 assimilation under ambient atmospheric CO2 conditions, and the increase was close to that by CO2 enrichment." Most interesting of all, in this regard, they report that the combined treatment of "plants with BR application under CO2-enriched conditions showed the highest CO2 assimilation rate, which was increased by 77.2% relative to the control." Likewise, they found that "an elevation in the atmospheric CO2 level from 380 to 760 ppm resulted in a 20.5% and 16.0% increase in leaf area and shoot biomass accumulation, respectively," while the plants that received the BR application "exhibited 22.6% and 20.6% increases in leaf area and shoot biomass accumulation, respectively." Most importantly of all, however, they report that, once again, the combined treatment of "CO2 enrichment and BR application further improved the plant growth, resulting in 49.0% and 40.2% increases in leaf area and shoot biomass, relative to that of the control, respectively."
In considering the above findings, it is clear that both atmospheric CO2 enrichment and BR application work wonders in promoting the early growth and development of cucumber plants, thereby providing hope that the two phenomena - one due to the direct effects of man (BR application) and one due to humanity's indirect effects (the mining and burning of fossil fuels) - working together and in concert with still other crop improvements that may possibly be devised, will yet enable Earth's growing human population to successfully feed itself near the midpoint of this century, when it is estimated there will be another two billion people inhabiting the planet.
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