Light quality and dormancy overcoming in seed germination of Echium plantagineum L. (Boraginaceae)

Abstract Light is considered a factor that influences the seed germination of many weed species, and it can signal whether the environmental conditions are favorable or are not favorable for germination. We aimed to study if there is an influence of light quality and dormancy overcoming in seed germination of Echium plantagineum L. We carried out a 2 x 6 factorial experiment, with and without dormancy overcoming with potassium nitrate followed by immersion in gibberellic acid; six light qualities, obtained through the light filters: blue, green, red, far-red, white light and absence of light. The evaluations performed were germination speed index (GSI), average germination time (AGT), germination at the four and 14 days after seeding (DAS), accumulated germination and relative frequency of germination. We observed significant interaction among the light qualities and seed dormancy overcoming or not for the studied variables. There was no significant effect of light qualities, in the evaluated variables, when performing dormancy overcoming, presenting germination above 90% in all the light qualities. However, without dormancy overcoming, we observed greater GSI, germination at four and 14 DAS for the red light filter with 5, 4, 29 and 45%, respectively. When the seeds were submitted to the absence of light, and without dormancy overcoming, there was only 7% of germination at 14 DAS. The seeds of E. plantagineum presented greater germination under incidence of red light, without dormancy overcoming, being classified as preferably positively photoblastics, provided that the dormancy is not overcome.摘要：光照是影响诸多杂草物种种子萌发的关键因子之一，可作为环境条件是否适宜种子萌发的信号。本研究旨在探究光照品质与破除休眠对蓝蓟（Echium plantagineum L.）种子萌发的影响。本试验采用2×6完全因子设计，设置2组休眠处理：经硝酸钾浸种后辅以赤霉素浸泡以破除休眠，以及未进行休眠破除处理；同时设置6种光照品质处理，通过滤光片获得蓝光、绿光、红光、远红光、白光，以及完全黑暗条件。测定指标包括萌发速率指数（germination speed index, GSI）、平均萌发时间（average germination time, AGT）、播种后第4天和第14天的萌发率（days after seeding, DAS）、累积萌发率以及萌发相对频率。结果显示，各光照品质处理与休眠破除与否之间对所有测定指标均存在显著交互效应。经休眠破除处理的组中，光照品质对各测定指标无显著影响，所有光照处理下的种子萌发率均高于90%。但在未破除休眠的组中，红光滤光处理下的萌发速率指数、平均萌发时间、播种后第4天及第14天的萌发率分别为5、4、29%和45%，各项指标均优于其他光照处理。而在未破除休眠且完全黑暗的处理组中，播种后第14天的萌发率仅为7%。未破除休眠的蓝蓟种子在红光照射下萌发效果最优，因此在未破除休眠的前提下，该物种可被归类为专性正光性种子。