Background: When mineral nutrients are present in excess or in inadequate amounts, their effects can be severe in plants and can be considered as abiotic stress. In this study, we report how hormonal levels in barley cultivars respond to the toxic effect of boron, an essential plant micronutrient. Materials and Methods: Two different barley (Hordeum vulgare) cultivars (Vamik Hoca and Efes 98) were used as a study material. Boron was applied in three different concentrations (0, 10, 20 ppm) to plants that had grown from seeds for four weeks. Plants were harvested, stem-root length and stem-root dry-fresh weight content were determined. For further analysis, chlorophyll, total protein, endogenic IAA and ABA content analyses were carried out. Results: According to the data obtained, plant growth and development decreased with increasing boron concentrations. With increasing boron concentrations, soluble total protein increased in both cultivars. Boron application led to increased endogenic IAA content in both cultivars. 10 and 20 ppm boron application led to increased endogenic ABA content in Vamik Hoca cultivar whereas endogenic ABA content decreased in Efes 98. Absence of boron application led to increased endogenic IAA and ABA content in both cultivars. Conclusions: As a result, the response to boron is different in the two cultivars and Efes 98 may be more resistant to the toxicity than Vamik Hoca cultivar.
Potato crop production in Turkey ranks on the thirteenth place in the world. Toxicity is a problematic issue for some parts of the Turkish soils. Hence, it is very important to clarify the physiological responses of plants to toxic mineral stress. In this study, two different potato cultivars À Solanum tuberosum cv. Resy and Solanum tuberosum cv. Agria À were used as a study material. Excess boron was applied in two different concentrations (5 mmol/L and 12.5 mmol/L) 32 days after planting the tubers. Plants were harvested at the end of 15 days of excess boron application. Chlorophyll fluorescence (Fv/ Fm) was measured. Shoot height and shootÀroot fresh weight contents were determined. Analyses were carried out for the contents of the endogenous hormones indole-3-acetic acid (IAA) and abscisic acid (ABA) by using gas chromatographymass spectrophotometry (GS-MS). According to the obtained data, plants' shoot height did not change, whereas the shoot's fresh weight decreased significantly with increasing of the boron concentrations in cv Resy, by applying 12.5 mmol/L boron. With 12.5 mmol/L boron, the photosynthesis was negatively affected in both cultivars. Boron application led to increased endogenous IAA and ABA content in both cultivars. As a result, cv. Resy showed more resistance to excess boron. Findings on the hormone metabolism and chlorophyll fluorescence in different cultivars will shed a light on understanding the physiological response to excess mineral stress.
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