Tetrazolium viability test method for micro-seeds of the endangered plant Deinanthe caerulea

Abstract

Deinanthe caerulea is a rare perennial herb endemic to China that has high medicinal and ornamental value. Seeds of D. caerulea are tiny with a thousand seed weight of only 200 mg. Thus, classical germination tests are difficult to apply in this species and a rapid and accurate method for determining seed viability becomes an important prerequisite for species conservation, introduction and domestication. When using the tetrazolium (TTC) topographical staining method, removing the seed coat for TTC penetration is not practical. Therefore, in this experiment, we tried a hypochlorite seed treatment before the TTC test for discolouring and improving permeability of the seed coat. For three different seed samples, we found that treatment with 1% sodium chlorite solution for 30 minutes was the best pre-treatment, followed by staining with a 0.5% TTC solution for five hours. Staining patterns of embryos can then be observed under a microscope without any further preparation of the seeds. Only completely stained embryos were classified as viable. Simultaneously, germination tests were performed at different temperature and light regimes. The best regime was alternating 25/15°C and constant light at 3000 lx. Average germination percentage of the three samples was 79.75%, whereas viability was 86.77%. The results showed that a hypochlorite treatment before TTC staining is a versatile method for improving practicability of viability testing in Deinanthe caerulea.