Studies On The Relationship Between Petiole Spots Of Chinese Cabbage And Nitrogen Metabolism

As one of the most important economic crop and extensive cultivated vegetables, Chinese cabbage (Brassica campestris L. ssp. Pekinensis) was originated from China. It is the main exported vegetable in our country. But a new physical disorder called petiole spots (gomasho called in Japan) in Chinese cabbage has greatly affected on the quality and exportation. Resistant to petiole spots cultivars Lubai 15 and M36, compared to susceptible cultivars 87-114 and PI5-1 were studied under no nitrogen level (CK) and high nitrogen (540kg/hm~2 pure nitrogen) level. The main results were as follows:1. Petiole spots symptoms mostly occurred in the filed after head formation and continue to be surious during storage. A large number of black spots, 1-2 mm in diameter, first appeared on the midribs of outer heading leaves, then spread to the middle leaves and becoming larger and larger as the cabbage growing. The symptoms in different genotypes cabbages were different.2. Nitrate reductase (NR) activities of the four cultivars were higher in high nitrogen level than in CK. As the cabbage development, the NR activity was increased in petioles. The NR activity increased more rapidly in leaves- than in petioles when treated with high nitrogen. Whether in CK level or in high nitrogen level, the NR activities of resistant cultivars were higher than susceptible cultivars.3. No matter in CK or high nitrogen level, glutamine synthetase (GS) activities of the four cultivars were higher in leaves than in petioles. The GS activity in high nitrogen level was greater than in CK, but not always.