Vegetable yields should show at least moderate increases with elevated [CO2]. Responses of lettuce, carrot and potato are described in more detail in section 10.3. In addition, responses of four glasshouse crops - cucumber (Cucumis sativus L.), pepper, tomato and eggplant (Solanum melongena L.) - to CO2 enrichment have been studied by Nederhoff (1994) in the Netherlands. In cucumber given [CO2] of 620 |mmol mol-1, fresh-weight fruit harvest increased by 34% compared with a crop grown at 364 |mmolmol-1. Two-thirds of this increase was caused by a greater number of harvested fruits and one-third by an increased average fruit weight. In pepper, increasing [CO2] from 300 to 450 |mmol mol-1 increased fruit production by 46%. One-third of this increase was caused by a shift in allocation, and the remaining two-thirds was caused by increased CO2 assimilation rate.

Disorders of leaf and shoot growth occurred in CO2-enriched tomato and eggplant. Depending on the incidence of the short-leaf syndrome in tomatoes, yield increases varied from 0 to 31%. In eggplant, yield increases were 24% even though active leaf area was reduced. Fruit quality was not affected by [CO2] enrichment in any of the greenhouse crops in the study. In a greenhouse tomato study in Raleigh, North Carolina, USA, cooling was used to increase the length of time the tomatoes could be [CO2] enriched. While yield increases of up to 35% were seen, they occurred only if the duration of enrichment was at least 90% of the daylight hours (Willits and Peet, 1989). In two onion (Allium cepa L. Cepa group) cultivars (Daymond et al., 1997), an increase in [CO2]

shortened time to bulbing, but the time from bulbing to bulb maturity was delayed. For the two cultivars at elevated [CO2], increases in bulb yield of 28.9-51% were due to an increase in the rate of leaf area expansion and the rate of photosynthesis during the pre-bulbing period as well as (or in addition to) the longer duration of bulbing.

Guide to Alternative Fuels

Guide to Alternative Fuels

Your Alternative Fuel Solution for Saving Money, Reducing Oil Dependency, and Helping the Planet. Ethanol is an alternative to gasoline. The use of ethanol has been demonstrated to reduce greenhouse emissions slightly as compared to gasoline. Through this ebook, you are going to learn what you will need to know why choosing an alternative fuel may benefit you and your future.

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