Study On The Stem Biochemical Components In Rapeseed Andtheir Relationship With Lodging Characters

Rapeseed(Brassica napus L.) occupies the dominant position in oil crops production in our country. In recent years, oil quality of rapeseed in China has been significant improvement and production patterns have been gradually converted to mechanized production mode, which greatly improves the production efficiency of rapeseed. However, in actual production, lodging with high frequency becomes the main factor that restricts mechanization production. Lodging not only results in poor quality of rapeseed, but also makes difficult in mechanized harvesting operations. Those seriously affected the efficiency in rapeseed production. These experiments conducted with different varieties and cultural practices to explore the differences in lodging characters and biochemistry components in stems. The relationships between lodging and stem biochemistry components were further investigated. These results could provide the theoretical basis to screen out high yielding and high lodging resistant rapeseed with the corresponding sowing date, planting density and nitrogen rates. The results showed that:1. Significant differences were found in the grain yield per plant among varieties. The difference in pod number per plant was the greatest among the yield components. Root crown diameter and bending force were two indicators of the most obvious differences among varieties. The root crown diameter, bending force significantly positively correlated with yield per plant and oil content. An increase in the root crown diameter and stem bending force coulid synergistically improve the yield and quality of rapeseed.2. The contents of cellulose, acid-insoluble lignin and total lignin in stem were more significantly different among varieties. Bending force in varities was significantly positively correlated with the contents of soluble sugar, cellulose and carbon in the stem of strong lodging varieties, and it was significantly negatively correlated with the contents of acid-insoluble lignin,total lignin and nitrogen in the stem of weak lodging varieties. The contents of cellulose, acid-insoluble lignin and total lignin in stem were more significantly different among varieties. Therefore, we speculated that rapeseed with more cellulose, acid-insoluble lignin and total lignin in the stemhad good lodging resistance.3. From the results, two varieties of high yielding and lodging resistance( Fengyou 520 and Huashuang 5) were selected. The two varities have morphological characteristics such as thicker in root crown diameter, higher bending force, lower branches starting point, shorter main inflorescence, more number of pods per plant; low acid insoluble lignin and total lignin content, but high soluble sugar, cellulose and carbon content in the stem.4. Interactions of sowing time and nitrogen rate on the root crown diameter, bending force, root-shoot ratio, stem lodging index etc reached extremely significant level. Around September 20, planting rapeseed combined with 360 kg hm-2 nitrogen reached the highest yield,with the maximum lodging resistance. Meanwhile, the root crown diameter and bending force were maximum, while lodging index was minimum; and stem acid-insoluble lignin, acid soluble lignin, total lignin, hemicellulose and cellulose contents attained the highest while soluble sugar content was the lowest.5. Interactions of sowing time and the density on the lodging index were significant. Sowing arround September 20, combined with 150 thousand plants hm-2, lodging resistance was the maximum, with the largest root crown diameter, root-shoot ratio and bending force, while the lodging index was minimum. At the same time, stem acid-insoluble lignin and total lignin contents were the lowest, while soluble sugar and cellulose contents were the highest. Yield per plant and oil content decreased, while the yield per plot increased firstly and then decreased with increasing density.6. Delayed sowing time reduced rapeseed lodging resistance, roots crown diameter, root-shoot ratio and bending force, while increased lodging index, soluble sugar and cellulose reduced, resulted in reduced yield potential. In conclusion, suitable sowing time(around September 20) with middle nitrogen rate(240 to 360 kg hm-2) and reasonable sparse planting(density of 150 to 300 thousand hm-2) created the highest stem lodging resistance and yield in rapeseed.7. The initial flowering stage and the full-bloom stage were critical stages when lodging resistance regulated by the biochemical components among four periods of rapeseed, which had great effect on bending force. Cellulose played the most important positive role in regulating bending force. The higher the cellulose content, the greater the lodging resistance of the rapeseed.