Refining the tetrazolium test for evaluation of Cattleya labiata and C. tigrina seeds viability

Abstract

The evaluation of seed physiological quality can help taking quick decision about the use or disposal of lots for conservation. The tetrazolium test is one of the most traditional in the analysis of seeds quality. Optional preconditioning procedures have improved the efficiency of this test. This work compared the efficiency of different preconditioning procedures, the buffered solution, concentrations and exposure time to tetrazolium solution in assessing the quality of orchid seeds of Cattleya labiata and Cattleya tigrina lots. The analysis was made through magnification of digital images. For preconditioning evaluation, two seed lots were aliquoted and submitted to different treatments: 10% sucrose solution, 10% glucose solution and water at room temperature for 24 hours. After preconditioning, seeds were immersed in tetrazolium solutions -prepared with buffer or water -at concentrations of 0.1, 0.5 and 1.0% for periods of 3, 12 and 24 hours, at 40 °C, in a water bath, in the dark. The experiment design was arranged in a factorial 4x3x3x2 and the mean comparison was made by Tukey test at 5% probability. Tetrazolium test in preconditioned orchid seeds allowed better visualization of red viable seeds. Tetrazolium test in orchid seeds preconditioned in glucose 10% solution or sucrose 10% solution was more effective for viable seeds visualization. Diluting tetrazolium salt in buffered solution or water made no difference for the results. Maintaining seeds in contact with tetrazolium 1% solution for 24 hours provided the higher viability values for both seed lots.

Seed viability test of orchids native to the Brazilian Savanna1

“…An essential factor for the formation of a native orchid seed bank is the identification of the viability of stored seeds which can be used for propagation and conservation of the species, since this viability may be affected even under favorable conditions (Doria 2010, Hosomi et al 2017, Mercado et al 2020. Therefore, the use of fast tests such as tetrazolium is important, mainly to decision-making regarding the management of seed banks (Marcos Filho 2015).…”

“…Methodologies for the tetrazolium test in Orchidaceae seeds have been proposed in the literature (Hosomi et al 2011, Hosomi et al 2012, Hosomi et al 2017, Macedo et al 2014. However, changes in the seed pre-conditioning and conditioning procedures for the test may increase the seed efficiency, since these changes aim to improve the visualization of viable seeds (Salazar & Gélvez 2015, Custódio et al 2016, Seaton et al 2018, Mercado et al 2020.…”

“…f., soaking in distilled water for 24 h provides better results for visualizing the seed viability (Lallana & Garcia 2013). Hosomi et al (2017), evaluating the tetrazolium test on Cattleya labiata and C. tigrina seeds, report that pre-conditioning in a 10 % glucose or 10 % sucrose solution is more effective for visualizing viable seeds. Mercado et al (2020) found that the use of deionized water improves the efficiency of the tetrazolium test on Epidendrum fimbriatum, E. microtum and E. elongatum seeds.…”

Methodology of the tetrazolium test for identifying viable seeds of orchids of the genus Cattleya native to the Brazilian Cerrado

“…According to methodology adapted from Hosomi, Souza, Custódio and Machado (2017), forty-eight 0.001 g samples of stored seeds of each species were placed in test tubes. Sets of twelve 10 mL tubes were subjected to preconditioning (P) with three soaking pretreatments: P1 -no soaking (control); P2 -3 mL of sucrose solution (10%) for 24 hours; and P3 -3 mL of distilled water for 24 hours.…”

“…For C. walkeriana, the highest %VS value was observed when seeds were preconditioned in sucrose and subsequently conditioned in ambient temperature (88%), not differing statistically between preconditioning control and distilled water with subsequent conditioning in ambient temperature (67 and 69%, respectively) and neither of the preconditioning or sucrose in the conditioning water bath (68%) (Table 2). Hosomi et al (2017) at ambient temperature aided in the accuracy of the tetrazolium test for both C. nobilior and C. walkeriana. Thus, the temperature during the test may be a determining factor in improving the visualization of viable seeds of these species.…”