Research on Difference of Nitrate Content among Cultivars of Chinese Mustard (Brassica campestris L. ssp. chinensis (L.))
Date Issued
2011
Date
2011
Author(s)
Chen, Kung-Feng
Abstract
Chinese mustard (Brassica campestris L. ssp. chinensis (L.)), an important leafy vegetable in Taiwan, often accumulates nitrate when nitrogen fertilizer is over applied especially under low light intensity. The accumulation may be different among cultivars. In the present study, 13 Chinese mustard cultivars were first evaluated their difference in nitrate accumulation in summer. The amount of nitrogen fertilizer was applied according to the suggested guideline (N:120 kg‧ha-1; P2O5:90 kg‧ha-1, K2O:120 kg‧ha-1). The 4 selected cultivars were used to study the effect of nitrogen fertilizer on seasonal nitrate accumulation in winter and spring. The relationship among cultivars, amount of nitrogen fertilizer, and seasonal effect in Chinese mustard for nitrate accumulation were studied.
In summer, nitrate content of whole plant in all the lines tested were significantly different and did not over accumulate (< 2500 mg∙kg-1) except B317. In winter, The nitrate content of the whole plant of 4 selected lines was higher than 4500 mg‧kg-1 when the N fertilizer was same as what applied in summer. The fresh weight of 4 selected lines was not increased as N fertilizer increased, but nitrate content of whole plant was significantly increased. In spring, the similar result was obtained.
Under low light intensity and low temperature conditions, the photosynthetic rate and nitrogen assimilation capability in the leaf blade of Chinese mustard decreased, which resulted in unassimilated nitrate accumulated in leaf blade. The transport of nitrate to petiole was increased as the nitrate accumulated in leaf blade increased. In Chinese mustard, petiole accounts for 30%-80% of whole plant in weight, and the nitrate content in petiole was 1.5 to 2 folds than in leaf blade. Thus, the nitrate content in petiole might overwrite the difference in leaf blade among cultivars in winter.
For producing low nitrate content vegetables, it ought to have different fertilizing guidelines for different seasons. Under low light intensity and low temperature conditions, the nitrate content of the 4 selected lines exceeded 4500 mg‧kg-1 when 120 kg‧ha-1 N fertilizer was applied, whereas the nitrate content of which was under 4500 mg‧kg-1 when 60 kg‧ha-1 N fertilizer was applied. However, the fresh weight was traded off. Thus, the amount of N fertilizer should be between 120 and 60 kg‧ha-1.
For screening low nitrate content cultivars, the assimilation capability of leaf blade and the ratio of petiole in whole plant should be considered at the same time. A negative correlation between growth rate and whole plant nitrate content might be a breeding index especially for winter cultivars.
Subjects
Chinese mustard
cultivar
nitrogen application rate
season
nitrate accumulation
petiole
screening
photosynthesis
SDGs
Type
thesis
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