Germination of physically dormant seeds of Colubrina glandulosa Perkins (Rhamnaceae)
2020
Pinto, Tassiane Terezinha | Geisler, Graziela Elizabeth | Santos, Marisa | Paulilo, Maria Terezinha Silveira
This study analyzed morpho-anatomy and histochemistry of seed coats, the effect of temperature on breaking seed dormancy and changes in water gap of Colubrina glandulosa Perkins (Rhamnaceae). Thermal shocks, alternating temperatures and forest environments were tested to analyze the break of physical dormancy. Morpho-anatomical studies were made using fresh or fixed tissue observed under stereoscopic, optical and scanning microscopes. To perform histochemical studies, sections of fresh seeds were left to stain in different reagents and then observed under epifluorescence microscope. Seedling emergence in forest edge and forest understory was similar to seed germination under laboratory conditions, indicating that the differences between environments had no effect on the germination of seeds. The germination ability of fresh seeds was lost in forest gap environments or when stored. Alternating temperature and thermal shocks have not alleviated the physical dormancy of seeds with the exception of dormancy acquired during seed storage. The results of germination suggest the presence of sensitive cycling phenomenon in these seeds. The seed coat features were similar to those of species undergoing physical dormancy, presenting a layer of macrosclereids impregnated with substances impermeable to water, as callose and lignin, in addition to compact sclerenchymatic tissue. Treatments of sulfuric acid and alternating temperatures increased the width and number of cracks around the hilar fissure; however, water could not penetrate the seed through these cracks, suggesting that water enters through the hilar slit.
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