As expected, tissue acidity increased substantially during the night in all the CAM plants examined, but no day–night changes in acidity whatsoever were observed in regular plants, again implying distinctive differences in metabolism within their tissues. Secondly, in an experiment conducted on 70 different species from 40 plant families growing in Panama, the authors tested the extent of acidity changes in the plants’ tissues during the day–night cycle. One is that the fixation of carbon dioxide at night in CAM plants is always associated with the accumulation of malic acid, whereas this particular organic acid only accumulates in normal plants during the daytime. In their new analysis, Winter and Smith conclude that organic-acid metabolism in CAM plants differs from normal plants in two crucial respects. Some scientists have proposed that, since the ability to accumulate organic acids is widespread in the plant kingdom, there may be no general barriers to the bioengineering of CAM photosynthesis. A central question for Winter and Smith, however, was whether regular plants could easily integrate this adaptation into their photosynthetic metabolism. This enables them to take up carbon dioxide from the atmosphere in the dark, rather than during the hotter daylight hours, which greatly reduces evaporative water loss through the stomatal pores on their leaf and stem surfaces.īecause light energy is not available at night, the carbon dioxide absorbed is temporarily stored in the plant as organic acid and is then transformed back into carbon dioxide during the following day, when photosynthesis can proceed.
Many species from hot semi-arid areas have evolved a form of photosynthesis called crassulacean acid metabolism (CAM), commonly found in succulent plants. Yet not all plants do this in exactly the same way. Plants acquire their energy through photosynthesis, the process by which sunlight, carbon dioxide and water are harvested and transformed into sugars and other organic compounds.
Their findings indicate that bioengineering drought-resistant plants may not be as easy as some scientists have proposed. But is it really possible to achieve this? Understanding the evolution of plants’ abilities to survive these extremes is part of a new study by Klaus Winter, senior staff scientist at Smithsonian Tropical Research Institute, and J. As climate change increases the frequency of weather extremes, interest has been growing in bioengineering crop plants with the same drought-tolerance mechanisms present in plant species from very hot areas. Drought and high temperatures often cause significant yield losses in valuable food crops.
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