白沙蒿种子萌发特性的研究 II. 环境因素的影响

白沙蒿(Artemisia sphaerocephala Kraseh．)是中国西北部沙漠的流动及固定沙丘上广泛分布的优势种灌木。白沙蒿种子为需光种子，种子在光下萌发而在黑暗中受到抑制。种子萌发的适宜温度为25℃，在10℃和30℃萌发速率和萌发率都很低，萌发在5℃受到抑制。种子在沙中被埋越深，其萌发速率和萌发率就越低。在沙平面下2cm或更深层沙土下出苗率为零。但是，当将种子上层沙土移走，只保留0.5cm沙土覆盖种子，这些种子的萌发率达到原先就位于沙土下0.5cm的种子的萌发率，但是后者的萌发速率较高。土壤水分含量越高，从1.7％到14.7％，其萌发就越快。土壤水分含量从19.4％起，种子的萌发受到了延迟，苗的发育受到了抑制.

SEED GERMINATION IN ARTEMISIA SPHAEROCEPHALA II. THE INFLUENCE OF ENVIRONMENTAL FACTORS

Artemisia sphaerocephala Krasch. is a dominant shrub in largeareas of activ e and stabilized sandy deserts of northwest China. The seeds of A. sphaerocep hala are light sensitive, germinating in light but poorly in dark. The optimal temperature for germination is 25 ℃. At 10 ℃ and 30 ℃ germination velocity was slow and reached low total percentages, at 5 ℃ germination was inhibited. T he deeper the seeds were placed in sand, the lower and slower was their germina tion. No seedlings emerged from achenes located at 2 cm or more cm. However, whe n t he upper layer of sand was removed leaving deep buried seeds at under just 0.5 cm of sand, their germination reached the same percentages as the seeds located 0.5 cm deep from the beginning of wetting, but at a faster rate. With higher san d moisture content, from 1.7% to 14.7% water content, germination was earlier. F rom 19.4% soil moisture germination was delayed and seedlings remained undeveloped.