Germination of Echium plantagineum L. seeds submitted to dormancy overcoming and variations in temperature, light and depth of sowing

Abstract

-The objective of this study was to evaluate methods of overcoming dormancy, light regimens, temperature and depth of sowing variations in the physiological quality of Echium plantagineum seeds. The diaspores (agglutinated fruits from the seeds) were submitted to treatments using accelerated aging, potassium nitrate and gibberellic acid to overcome dormancy. A 7 x 2 factorial design was used to evaluate the temperatures (5, 10, 15, 20, 25, 30 and 35 °C) and light regimens (presence or absence of light). A 6 x 2 factorial design was used for sowing depth (0, 1, 2, 3, 4 and 5 cm) and soil coverage (presence or absence of straw). In all experiments, a completely randomized design with four replicates of 50 diaspores was used. The main evaluations were germination, first germination count, germination speed index and emergence. The seeds showed dormancy, which was overcome by the immersion of the diaspores in potassium nitrate and gibberellic acid. The ideal temperature for germination was 20 °C, showing greater germination in the presence of light, considered as preferentially positively photoblastic. The highest germination percentage occurred when the diaspores were positioned on the soil surface in the presence of straw.Index terms: gibberellic acid, purple flower, photoblastism, potassium nitrate, straw. Germinação de sementes de Echium plantagineum L. submetidas à superaçãoda dormência e variações na temperatura, luz e profundidade de semeadura RESUMO -Objetivou-se avaliar métodos de superação da dormência, regimes de luz, variações da temperatura e profundidade de semeadura na qualidade fisiológica de sementes de Echium plantagineum. Para isso, os diásporos (fruto concrescido das sementes) foram submetidos a tratamentos utilizando envelhecimento acelerado, nitrato de potássio e ácido giberélico para a superação da dormência. Utilizou-se um fatorial 7 x 2 para avaliar temperaturas (5, 10, 15, 20, 25, 30 e 35 °C) e regimes de luz (presença ou ausência). Já para profundidade de semeadura (0, 1, 2, 3, 4 e 5 cm) e cobertura de solo (presença ou ausência de palha) utilizou-se um fatorial 6 x 2. Em todos os experimentos foi adotado o delineamento inteiramente casualizado com quatro repetições de 50 diásporos. As principais avaliações realizadas foram germinação, primeira contagem de germinação, índice de velocidade de germinação e emergência. As sementes apresentam dormência, sendo superada pela imersão dos diásporos em nitrato de potássio e ácido giberélico. A temperatura ideal para a germinação foi 20 °C, apresentando maior germinação na presença de luz, sendo consideradas fotoblásticas positiva preferencial. A maior porcentagem de germinação ocorreu quando os diásporos foram posicionados na superfície do solo, na presença de palha.Termos para indexação: ácido giberélico, flor roxa, fotoblastismo, nitrato de potássio, palha.

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

“…These results corroborated in part with the ones found by Roso et al (2017), in which the authors classified E. plantagineum as preferably positively photoblastic, presenting greater germination when the seeds were exposed to light. In this work, we verified that the light provides stimulus to germination if the dormancy overcoming is not carried out; however, when overcoming the dormancy, the germination occurs independent of light stimulus, indicating that the dormancy of this species can be related to a combination of factors.…”

“…The experiments were conducted in germination chamber of Biochemical Oxigen Demand (B.O.D.) type at temperature of 20 °C and photoperiod of 24 hours of artificial light inside the chamber (30 μmol m -2 s -1 de illuminance) (Brasil, 2009;Roso et al, 2017). We used the completely randomized experimental design (CRD) with four repetitions of 50 diaspores (carcerulus: fruit agglutinated with the seed) totaling 200 diaspores by treatment.…”

“…In the treatments submitted to the dormancy overcoming, we performed the soaking of the diaspores in potassium nitrate solutions (0.2%) for 12 hours, followed by immersion in gibberellic acid (500 mg L -1 ) for 48 h, occurring the washing of the diaspores after each period of immersion, for 10 min in running water (Roso et al, 2017).…”

“…Besides, it has phenotypic plasticity demonstrated by the variation of morphological characteristics, plant height, size and fruit mass, triggered in response to abiotic factors (Piggin, 1976;Konarzewski et al, 2012). Another form of adaptability to the environmental conditions is its capacity of seed production, which can exceed 6000 seeds per square meter in high infestations, presenting dormancy that contributes for the distribution of the emergence flows in time and permanence in soil seed bank (Piggin, 1976;Roso et al, 2017;Florentine et al, 2018). It characterizes itself by the scorpioid inflorescence and fruit denominated carcerulus (indehiscent dry fruit and one-seeded), whose seed remains united to the fruit, being a unit of dissemination and propagation (Moreira and Bragança, 2010;Souza and Lorenzi, 2012).…”

Germination of Stigmaphyllon blanchetii Seeds in Different Temperatures and Luminosity

“…The same behavior was found in Myracrodruon urundeuva seeds (Silva et al, 2002). Echium plantagineum seeds are considered to be preferentially positive photoblastic (Roso et al, 2017). Seeds can also be classified according to light in relation to phytochrome forms.…”