Soluções crioprotetoras na conservação de sementes de orquídea estrela e orquídea bambu em nitrogênio líquido

Abstract

An alternative for the conservation of orchid species threatened with extinction is the seeds preservation for long periods by cryopreservation. This work aimed to evaluate the influence of cryogenic solutions on the orchids Epidendrum radicans and Arundina bambusifolia seeds cryopreservation in liquid nitrogen. Seven treatments were performed: 0.4 M sucrose; 2 M glycerol; PVS1; PVS2; PVS3; PVS2 + 1% phloroglucinol and the control. After liquid nitrogen removal, half of the seeds were subjected to tetrazolium test, and another half was in vitro cultured. After 30 days seed germination was evaluated. There was no significant difference between A. bambusifolia and E. radicans in tetrazolium test and seeds germination. On the other hand, it was observed that in A. bambusifolia tetrazolium and seed germination tests the solutions of PVS1, PVS2, PVS2 + 1% phloroglucinol showed the best results. E. radicans seeds with 4% water content cryopreservation does not require the use of cryoprotectant. On the other hand, cryoprotectant´s use resulted in positive effect in maintenance and viability preservation of A. bambusifolia seeds. PVS1, PVS2 and PVS2 + 1% phloroglucinol showed best seeds survival rates after cryopreservation in liquid nitrogen.

Degree of moisture in seeds for the cryopreservation of orchids native to Brazil

“…The tetrazolium test was efficient in evaluating the viability of the seed and made it possible to obtain results quickly and efficiently. This test has also been used successfully to evaluate the seeds of other cryopreserved orchids, as demonstrated by HIRANO et al (2005), VENDRAME et al (2014), HIRANO et al (2011), PAULA et al (2018) and SUZUKI et al (2018.…”

“…In most cases, when the moisture degree was lower, between 4% and 6%, the possibility of obtaining viable seeds is greater, which was in agreement with SAKAI et al (1991) when they stated that one of the most important steps in cryopreservation is the dehydration process, because it aims to prevent physical damage by the formation of ice crystals to the cells during the freezing period. In view of this information, some authors recommend the use of cryoprotective solutions in order to dehydrate the seeds, thus reducing the negative effects of the formation of ice crystals during the freezing process (VENDRAME et al, 2014;PAULA et al, 2018;SUZUKI et al, 2018). However, the use of cryoprotective solutions becomes costly and some components of these solutions can exert toxicity on the orchid's seeds, leading to the death of the embryo.…”