Effects of light level, time of harvest and position within field on the variability of tissue nitrate concentration in commercial crops of lettuce (Lactuca sativa) and endive (Cichorium endiva)

Contribution of different vegetable types to exogenous nitrate and nitrite exposure

“…In the first case, the boiling water is usually discarded and therefore a reduction in nitrate levels is expected. In regard to the soups, although The time of the day the plants were harvested was shown to have a significant effect on the variability of nitrate levels in lettuce, although with no consistent temporal trends (Weightman et al, 2006). However other studies failed to detect a significant relationship between nitrate levels and time of harvest within the day (Reinink, 1991).…”

“…Even among different samples of the same vegetable varieties, the range of concentrations may be large (Prasad & Chetty, 2008;Tamme et al, 2006;Thomson et al, 2007). Variations, within site, for plants growing in the same plot can be explained by differences in soil mineral nitrogen, and individual plant growth in response to localised areas of soil compaction, or variability in soil pH (Weightman, Dyer, Buxton, & Farrington, 2006).…”

Evaluation of response of lettuce (Lactuca sativa L.) to temperature and light stress

“…It was found that the light curve of photosynthesis in lettuce has a smaller slope, which indicates the ability of this species to fully absorb light with a low intensity, showing a good growth rate. Some authors have suggested that in lettuce a lower temperature and short-term shadowing may lead to a more intensive intake of nitrates and their utilization in the synthesis of proteins and the accumulation of biomass [10,15].…”

“…The lower intensity of transpiration at the water temperature of 12°C can be explained by the slow diffusion of water vapor through the stomata and sustained uptake of water from the roots. It has been established that at lower temperatures the incorporation of nitrogen in chlorophyll becomes more effective as a protective response of a plant, which has adaptive importance as this can enhance the photosynthesis [3,10].…”

“…Testing the adaptability of different plant species and varieties to light and temperature stress and creating resistant genotypes are a leading target of selection in agriculture [9]. Higher resistance of plants to abiotic stress can significantly increase their productivity and competitive power [9,10].…”