Echium plantagineum L. (boraginaceae): superação da dormência, respostas à temperaturas, luz e profundidades de semeadura

Abstract

Echium plantagineum is considered an annual invasive ruderal plant, possibly biennial, originating in the Mediterranean region and Western Europe, of easy adaptation, with up to 1,5 m of height, reproduced by seeds, and with potential to become weed. Besides being easy to adapt to different environmental conditions. Besides being easy to adapt to different environmental conditions. In view of the above, the objective of the work is to evaluate methods of overcoming dormancy, light regimes, temperature variations and seeding depths in the physiological quality of E. plantagineum seeds. Three experiments were conducted, two in the laboratory, in which Experiment I evaluated seed dormancy overcoming treatments with high temperature exposure times (42 °C) and humidity [TU] (100%) (24, 48, 72 and 96 h), immersion times in potassium nitrate (PN) (0,2%) (6, 12, 18 and 24 h), immersion in concentrations of gibberellic acid [GA] (250, 500, 750, 1000 and 1500 mg L-1), and PN + GA (12 h) + (125, 250, 375, 500 and 625 mg L-1). In Experiment II the seeds were submitted to different constant temperatures (5, 10, 15, 20, 25, 30 and 35 °C) in the presence or absence of light. Experiment III was conducted in a greenhouse, in which the seeds were allocated to different soil depths (0,0, 1,0, 2,0, 3,0, 4,0, and 5,0 cm) in the presence or absence of plant cover with ryegrass straw (Lolium multiforum L.). In general, the pre-germination treatments using PN and GA applied sequentially are favorable for overcoming dormancy, allowing maximum expression of vigor and germination of the seeds, making it possible to generate seedlings with normal primary structures. Seeds of E. plantagineum can be classified as neutral photoblasts, having a temperature of 20 °C as optimum for germination, variable from 10 to 30 °C. When the seeds were submitted to depths in the soil, there was a significant decrease of the emergence with the increase of the depth, being the seeds located at the surface showed greater emergence, occurring positive influence of the soil cover with straw.