向日葵生产在我县发展很快,1977年试种,1980年已发展到5.6万亩,不仅解决了吃油问题,还增加了社员的收入。但是,向日葵的空壳率很高,据统计,我县1980年向日葵的产量因空壳减产30%左右。为了解决这个问题,我们对形成空壳的原因进行了考察和试验,并找到了一些相应的防止措施。一、空壳与开花期气温的关系:在向日葵开花期间,如果气温超过20℃,则自花授粉不结实,只有异花授粉才结实。例如,杨庄公社16块向日葵地,其中有9块是6月下旬播种的,盛花期的平均气温27℃,平均结实率只有48%;2块地7月上旬播种,盛花期的气温为21℃,平均结实率为56%;4块地7月中旬播种,盛花期平均气温18.2℃,平均结实率为76.5%;7月下旬播种的1块地,盛花期的气温17.6℃,结实率为81%。因此,要提高向日葵的结实率, Sunflower production in our county developed rapidly in 1977, trial planting, in 1980 has grown to 5.6 million mu, not only solved the problem of eating oil, but also increased the income of members. However, the percentage of sunflower shell is very high. According to statistics, the output of sunflower in 1980 in our county is reduced by about 30% due to the shell. In order to solve this problem, we investigated and tested the reasons for the formation of hollow shells and found some corresponding preventive measures. First, the relationship between the shell and the flowering temperature: During the flowering of sunflowers, if the temperature exceeds 20 ℃, the self-pollination is not strong, only cross-pollination was strong. For example, Yangzhuang commune 16 sunflowers, of which 9 are sown in late June, the average temperature of full bloom flowering 27 ℃, the average seed setting rate of only 48%; 2 to sow in early July, flowering temperature of 21 ℃, and the average seed-setting rate was 56%. Four plots were planted in mid-July, with the average air temperature of 18.2 ℃ and the average seed-setting rate of 76.5%. In the area planted in late July, the temperature of full bloom was 17.6 ℃, 81%. Therefore, to improve the seed setting rate of sunflower,