Masahumi Johkan

Crop Production and Global Warming

Crop production will be affected by global warming, resulting in world-wide food shortages and starvation. Increased concentrations of carbon dioxide (CO2), one of the main substances responsible for global warming, will promote plant growth through intensified photosynthesis. Some reports indicate that a rise in the levels of CO2 would actually benefit plants, rather than harm them. The growth rates of C3 plants increase in response to elevated concentrations of carbon dioxide. Thus, global warming might increase plant growth, because of higher temperatures and higher levels of atmospheric CO2. High atmospheric temperatures caused by elevated concentrations of CO2 will induce heat injury and physiological disorders in some crops, which will decrease the incomes of farmers and agricultural countries. Photosynthesis is one of the most sensitive physiological processes to high temperature stress. Reproductive development is more sensitive than vegetative development to high temperatures, and heat-sensitivity differs among crops. In tomato, the optimal temperature for fruit set was reported as 21–24°C (Geisenberg and Stewart, 1986) or 22–25°C (Peet and Bartholomew, 1996), while pollen viability and release are adversely affected by high temperatures, and become major limiting factors for fruit set. Thus, global warming can have opposite effects on plant growth. From a long-term viewpoint, however, high atmospheric temperatures will drive the main sites of crop production further north, establishing new rules for the ‘right crop for right land’. Water shortages caused by global warming will be the greatest problem for crop production. Plants fundamentally rely on adequate fresh water, and agricultural water accounts for 70% of water use world-wide. As higher temperatures increase evaporation from water sources and decrease precipitation, arid regions will become further desertified. Particularly in semiarid regions, the cultivatable area will decrease because of drought, and this could result in famines and mass migration. As well, it is likely that there will be human conflicts over irrigation water and food. Global warming is thought to be related to strong hurricanes, cyclones, and typhoons. These extreme weather events can seriously damage crop production, and destabilize farm management and the lives of consumers. However, these agricultural problems are most likely to occur in the medium and long-term future. In this chapter, we summarize some of the agricultural problems and crop damage that result from global warming, and present some technical countermeasures (not political and administrative countermeasures) that could be used to ameliorate the effects of global

Management of nitrogen fertilizer application, rather than functional gene abundance, governs nitrous oxide fluxes in hydroponics with rockwool

AimsNitrous oxide (N2O) is a strong greenhouse effective gas (GHG); the primary human source of N2O is agricultural activities. Excessive nitrogen (N) fertilization of agricultural land is now widely recognized as a major contributor. In soil, the microbial processes of nitrification and denitrification are the principal sources of N2O. However, it remains poorly understood how conventional hydroponics influences GHG emission. Here, we compared GHG fluxes from soil and rockwool used for hydroponics under identical nutrient conditions.MethodsTomato plants (Solanum lycopersicum, momotaro) were grown in soil or by hydroponics using rockwool. In situ emissions of CH4, CO2, and N2O, and the abundance of genes involved in nitrification and denitrification were measured during cultivation.ResultsHydroponics with rockwool mitigated CO2 emission by decreasing the microbial quantity in the rhizosphere. Dilution of the nutrient solution significantly decreased N2O emission from rockwool. Although proliferation of nitrifiers or denitrifiers in the rhizosphere did not induce N2O emission, reuse or long-term use of rockwool induced a 3.8-fold increase in N2O emission.ConclusionsOur data suggest that hydroponics has a lower environmental impact and that adequate fertilizer application, rather than bacterial control, governs N2O fluxes in hydroponic cultivation using rockwool.

Morphological Variation, Growth, and Yield of Tomato Plants Vegetatively Propagated by the Complete Decapitation Method

Abstract The complete decapitation method (CDM), a new mass propagation technique in which adventitious shoots are regenerated from cut tomato (Solanum lycopersicum L.) stems, may induce variations similar to those observed in tissue culture. Morphological defect occurrence, growth, and fruit yield of CDM-regenerated clones were compared with those of plants produced from seed. Morphological defect frequencies of seedlings and clones were 3.5% and 6.0%, respectively. Leaf position of first fruit trusses was lower in clones than in seedlings; flower number, fruit set, and yield on first to third trusses were similar between clones and seedlings. The CDM-propagated vegetative clones are suitable for tomato nursery production.