Nitrate accumulation in leafy vegetables and its relationship with water

Abstract

Present studies show that nitrate accumulation is the major factor influencing the water uptake by vegetables, but there is lack of knowledge on how the relationship between nitrate and water concentrations in different vegetable tissues. We determined nitrate accumulation and water content in vegetables of rape, Chinese cabbage, and spinach under different nitrogen levels (experiment I), 29 spinach cultivars (experiment II), and 27 rape cultivars (experiment III). The results from experiments I-III showed a highly linear relationship between nitrate accumulation and water content, and the levels thereof in different organs of the vegetables revealed that the petiole exhibited the best correlation between them compared with the root and leaf blade. These suggest that (1) vegetables with high water content have high nitrate content, (2) water content in the petiole can be used to screen cultivars with low levels of nitrate accumulation, and (3) increasing soil water content in agronomic practice is essential to decreasing nitrate accumulation in vegetables.

Foliar application of molybdenum enhanced quality and yield of crispleaf lettuce (Lactuca sativa L., cv. Grand Rapids)

“…However, sustainable management of lettuce yield, as of many leafy vegetable crops, requires that N supplies are optimized to maximize crop growth and development, whilst minimizing economic inefficiencies and environmental contamination caused by soil nitrate (NO 3 -) leaching to groundwater (Dahan, Babad, Lazarovitch, Russak & Kurtzman, 2014). Furthermore, the excessive N fertilizer use may result in the accumulation of NO 3 -in the lettuce leaves and reduce the quality of the vegetable (Liu, Sung, Chen & Lai, 2014;Qiu, Wang, Huang, Chen & Yang, 2014). Nitrate by itself is relatively non-toxic; however, it may be endogenously transformed to nitrite, which can react with amines and amides to produce N-nitroso compounds (Santamaria, 2006).…”

Nitrate and oxalate in germplasm collections of spinach and other leafy vegetables

“…However, different results have been reported (Palaniswamy, 2003). For nitrate there are some old studies that examine the content in cultivars and germplasm collections (Lorenz 1978;Shen et al 1986;Groenword 1988) and a few more recent ones (Mou, 2008;Koh et al, 2012;Krężel and Kołota, 2014;Qiu et al, 2014). In contrast to nitrate, the deposition of oxalate is localized mostly in leaf blades (Kawazu et al, 2003;Stagnari et al, 2007).…”

“…Oxalate can react with calcium and other minerals, forming crystals which then inhibit mineral absorption (Noonan and Savage, 1999;Bohn et al, 2004). High nitrate levels are frequently found in vegetables from the Brassicaceae, such as rocket and radish, Chenopodiaceae, including plants such as beet root and spinach, but also in Asteraceae (lettuce) and Apiaceae (celery and parsley) (Santamaria et al, 1999;Ghidurus et al, 2012;Qiu et al, 2014). High oxalate concentration is most commonly found in vegetables from the Chenopodiaceae, but also Polygonaceae (Kameno et al, 1990;Ota and Kagawa, 1996).…”

Improving the sustainability of tobacco cultivation by optimizing nitrogen fertilization

“…The dynamic of nitrogen accumulation and redistribution is of particular relevance in tobacco since it could greatly affect quality/health aspects of the final product. Nitric-N in plant tissues generally increases with increasing N fertilization in different species and is affected by water availability (Qiu et al, 2014;Bashir et al, 2013). Considering that excess of nitrogen in tobacco tissues can react with alkaloids to form specific N-nitrosamines, one of the deleterious compounds identified in tobacco products, these data suggest that there is still a useful range of action (between 120 and 240 kg N ha -1 ) to improve N fertilization so to reduce harmful effects of smoking.…”