Germination Ecology of Ivy-Leaved Morning-Glory: an Invasive Weed in Soybean Fields, Iran

ABSTRACT: Ivy-leaved morning-glory (Ipomoea hederacea Jacq.) is an exotic species that is becoming an increasing problem in soybean fields of Golestan province, Iran. Because little information is available on the biology of this weed species in Iran, experiments were conducted to investigate the effects of different factors on seed germination and emergence of Ivy-leaved morning-glory. Maximum germination occurred at constant temperature of 20 oC (82%) and alternating temperature of 15/25 oC (94%). Germination was reduced with increasing salinity and drought stresses. Sodium chloride concentration and osmotic potential that inhibited 50% maximum germination were -1.64 and -1.03 MPa, respectively. Acidity was a limiting factor for the germination, due to inhibiting effect of alkaline conditions on germination. However, the results showed that high temperature pretreatment >100 oC decreased seed germination. Germination decreased from 82 to 3% as temperature increased from 100 to 130 oC. There was no significant difference between seedling emergence in burial depths of 1 to 10 cm, but emergence reduced with increasing burial depth from 10 to 14 cm, and no seedling was emerged from a depth of 15 cm. The results of the flooding experiment also revealed that the seeds of this species are sensitive to this stress, so that emergence was 9% after 3 d flooding.摘要：戟叶牵牛（Ivy-leaved morning-glory，学名Ipomoea hederacea Jacq.）是一种外来入侵物种，目前在伊朗戈勒斯坦省的大豆田中已造成愈发严重的危害。由于目前针对该杂草在伊朗境内的生物学特性研究信息较为匮乏，本研究开展系列试验以探究不同环境因子对戟叶牵牛种子萌发与出苗的影响。试验结果表明，其种子在恒温20 ℃条件下萌发率可达82%，在15/25 ℃变温条件下萌发率最高，达94%。随着盐胁迫与干旱胁迫程度加剧，种子萌发率显著降低。使最大萌发率受到50%抑制的氯化钠浓度与渗透势分别为-1.64 MPa与-1.03 MPa。酸碱度亦是限制其种子萌发的关键因子，碱性环境会对种子萌发产生抑制作用。此外，研究发现高于100 ℃的高温预处理会显著降低种子萌发率：当处理温度从100 ℃升至130 ℃时，种子萌发率由82%降至3%。在1~10 cm的覆土深度范围内，幼苗出苗率无显著差异；但当覆土深度从10 cm增至14 cm时，出苗率逐渐下降，且15 cm覆土深度下无幼苗出苗。淹水试验结果同样表明，该杂草种子对淹水胁迫极为敏感，淹水3 d后的幼苗出苗率仅为9%。