To determine the optimal time for harvesting the seeds of Gui 39722, which is the female parent of a newly-developed maize hybrid Guidan 0810, the cobs of Gui 39722 were harvested 31 （the first stage）, 34 （the second stage）, 37 （the third stage）, 40 （the fourth stage）, 43 （the fifth stage） and 46 （the sixth stage） d after pollination and oven dried at 38 ~C to constant weight. Then, the 1 000-ker- nel weight, germination rate and the agronomic traits of three-leaf seedlings were measured and compared. The results showed that the seeds of Gui 39722 harvest- ed 43 d after pollination （the fifth stage） had the greatest germination rate, seedling height, vigor index, root dry weight, shoot dry weight and germination potential, and high 1 000-kernel weight （very close to the highest level）, root length, number of roots per seedling and root-shoot ratio. Therefore, 43 d after pollination was the op- timal time for harvesting the seeds of Gui 39722, when the effective accumulated temperature after pollination reached 780.7 ℃ and the ear leaf dried. The seeds harvested at this stage had the highest yield and the best quality. Field sampling revealed that 89.00% to 95.00% （with an average of 91.15%） of the seedlings of six stages of seeds grew well.
[Objective] The aim was to explore the response of different maize vari- eties in Guangxi to drought stress and re-watering at tasseling stage, so as to pro- vide reference for study on drought resistance mechanism, breeding of drought-re- sistant varieties and selection of maize varieties for fall sowing. [Method] At the tasseling stage, total five degrees of drought stress （4, 8, 12, 16 and 20 d） and corresponding re-watering after drought stress were simulated by a tub planting ex- periment in greenhouse for five different maize varieties （Guidan 0810, Dika 008, Zhengda 619, Chenyu 969, Guidan 901）. Normal watering was set as the control. Sampling was carried out on Day 1 after drought stress and on Day 15 after re- watering, and the secondary root number, maximum root length, green leaf number, root dry weight and shoot dry weight were measured. At the harvest time, the ear yield per plant was measured. With yield as the basis, the drought resistance coef- ficient and drought resistance index were calculated. Cluster analysis was conducted for drought resistance coefficient. [Result] The shoot dry weight, root dry weight, secondary root number, maximum root length and green leaf number of maize in the treatment groups decreased compared with those in the control group. The ratio of each index between the treatment and control groups declined with the extension of drought stress. After re-watering, the re-growth amount of each index all de- creased as the stress time prolonged. Post-re-watering over compensation effect oc- curred in none of the indices except the maximum root length, after 4 days of drought stress. Under drought stress, the reductions of all the indices of Guidan 0810, Dika 008 and Zhengda 619 were smaller than those of Chenyu 969 and Guidan 901. After re-watering, the re-growth abilities of Guidan 0810, Dika 008 and Zhengda 619 were stronger than those of Chenyu 969 and Guidan 901. The drought resistance coefficients and drought resistance indexes of Guidan 0810, Dika 008 and Zhengda
