红花为长日照植物，在长日照条件下，莲座期显著缩短，植株变矮，整个生育期明显变短，但也有些品种如墨西哥矮，对日照长度的反应不甚敏感。多数红花品种在高温、长日照条件下，莲座期显著缩短，植株变矮，种子产量下降，但我国秋播红花产区北部的一些红花品种如ＢＪ－２４０在高温、长日照条件下莲座期不是缩短，反而无限延长，植株根本不能正常生长、开花结果。实验表明，将这些品种的种子萌发后置于０℃的冰箱中处理１５天后再播种，植株即能正常生长、开花、结果。在高温、长日照条件下不能正常生长发育的红花种质资源的发现，对于改良春型红花营养生长习性和提高产量具有重要意义。所发现的种子低温处理克服部分冬型红花不开花结果的方法，可直接在我国北方红花产区应用。对于发展我国红花生产具有重大意义。 

Safflower belongs to a long-day plant. The rosette habit period, plant height and the growth period duration were shortened under long-days. However, some cultivars such as Mexican Dwarf' are not sensitive to the photoperiod. Most of safflower germplasm, the rosette habit period and plant height were shortened and the seed yield decreased under high temperature and long-days. Whereas, some germplasm such as BJ- 240, came from Cao County, Shangdong Province, the rosette period was delayed indefinitely and the plant could never elongate, flower and fruit normally under higher temperature. The experiments indicated that after the sprouting seed of BJ-240 was treated with low temperature as 0 for a period of 15 days, the plant could grow and develop normally. The discovery of safflower
germplasm under high temperature and long- day will play an important role for improvement of the vegetative growth characteristics and increase the seed yield of spring safflower. The discovered method of seed treatment with low temperature for solving the problem to a part of winter safflower does not flower and fruit can be used directly in
safflower production in North China.