The hypothesis that selenium in soil affects the level of gibberellic acid accumulation involved in the regulation of spinach flowering was tested. The three-fold objectives of the present study were, first, to isolate and identify gibberellic acid present in induced and non-induced spinach (Spinacia oleracea L., cv. Bloomsdale) tissues grown in the presence of selenium, second, to quantify levels of this compound during the ontogeny of flower induction, and third, to study the effect on selenium-treated plants regarding the level of endogenous gibberellic acid. Plants were initially grown in a growth chamber under short photoperiod conditions (8 h of light at 25 oC and 16 h of darkness at 18 oC) for 7 weeks, and then half of the plants were transferred to a long photoperiod growth chamber (16 h of light at 30 oC and 8 h of darkness at 20 oC). Harvest of plants began 48 hours later and over a period of 12 days with 2-day intervals. Plants were subjected to a purification procedure involving preparatory solvent partitioning and reversed-phase high-performance liquid chromatography. The purified gibberellic acid was then identified and quantified using combined gas chromatography-mass spectrometry. When plants were transferred from floral non-inducing to inducing conditions, the gibberellic acid content increased with increasing levels of selenium treatment. Two additional and independent experiments were performed in which the above photoperiodic regime was employed and the temperature was kept constant at 30 oC and 20 oC throughout each experiment. These two experiments showed similar trends of decreasing gibberellic acid content under non-inducing conditions and, conversely, increasing under flower inducing conditions. Our study establishes a correlation between increased gibberellic acid level with the flowering of spinach grown in soil supplied with selenium.

Effect of selenium nutrition, temperature, and photoperiod on gibberellic acid accumulation in spinach plants

2019 Spring National Meeting

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