Influência da luz e de hormônios vegetais na germinação de sementes de Vellozia spp.

Abstract

Light and temperature are important factors in the regulation of germination, by influencing the adaptation of species to environmental change and promoting diversified germination characteristics. The species of Vellozia (Velloziaceae) produce small seeds with sensitivity to light dependent on temperature. This study was divided into two parts, the first held with 11 species Vellozia aiming to assess the time of exposure to light and the light quality (ratio V:VE) is necessary to achieve maximum seed germination. In this case, the seeds were exposed to different periods of exposure to white light (and only interrupted by dark pulses) and the reasons V: VE at 25 °C. A second experiment examined the relationship between the factors light and temperature with the hormones gibberellin (GA) and abscisic acid (ABA) during germination of species whose seeds are indifferent to light at high temperatures. Seeds of three species were subjected to treatment with ABA and gas and their inhibitors (fluridone and paclobutrazol) and two species were analyzed for hormonal profile during imbibition (25 and 40 °C). The seeds of Vellozia spp. require different periods of light exposure to achieve maximum germination (2 h to > 96 h when subjected to single pulse and 10 min > 8 h when exposed to pulses for 5 consecutive days interrupted by dark). The seeds that required long exposure times to light reached maximum germination only when exposed to higher grounds V: VE ( 0.77), while requiring less time required lower ratios R:FR (0,02 to 0,08). ABA inhibited germination regardless of light and temperature and fluridone promoted germination of the three species in the dark. The application of GAs not fully replaced the application of light and paclobutrazol reduced the germination of the two species tested. During imbibition decreased endogenous ABA levels only in the seeds imbibed at 40 °C and the levels of active GAs varied among species. The ration GAs/ABA remained constant at 25 °C and showed a tendency to increase when seeds were maintained at 40 ºC. We conclude that the seeds of Vellozia spp. require different exposure to light and reasons V:VE to achieve maximum germination, not presenting a standard for the genre; soaking at 40 °C decreased of endogenous levels of ABA, indicating that ABA modulates seed germination of Vellozia in response to light and temperature.