Alleviation of Heat Stress in Lavender and Sage by Salicylic acid and Calcium Chloride

Herbs and the essential oils are of both ornamental and practical value having medicinal, aromatic, culinary and other properties. In recent years, sales of herb plants have remained in the top ten in the potted flower market in Taipei where lavender (Lavandula spp.) and sage (Salvia officinalis) are among the popular kinds of herb. Many herbs that have been introduced from Europe, America, Japan and other temperate regions have a hard time adapting to the high temperatures and high humidity in Taiwan. The purpose of this study was to investigate the heat tolerance in some common-market varieties of lavender and sage with the infrared thermal imager and values of leaf relative injury. Six lavender varieties L. dentate, L. pinnata, L. x intermetia ‘Provence’, L. stoechas, L. angustifolia and L. x heterophylla and five sage varieties S. officinalis ‘Bergarrten’, S. elegans ‘Scarlet Pineapple’, S. officinalis, S. dorisiana and S. leucantha were included in the study. Secondly, the impact of using single and composite chemicals on lavender and sage to increase the tolerance for high temperatures was investigated. Infrared thermal imager and leaf relative injury values were used to classify the herbs into (1) Most heat tolerance – L. x heterophylla, L. pinnata; S. leucantha, S. elegans ‘Scarlet Pineapple’. (2) Moderately heat tolerance – of L. x intermetia ‘Provence’, L. dentate, L. stoechas; S. officinalis, S. officinalis ‘Bergarrten’. (3) Not heat tolerance – L. angustifolia; S. dorisiana. Heat tolerance of the herbs grown in semi-outdoor environment in terms of ornamental quality can be divided into (1) Most heat resistant – L. dentate, L. pinnata; S. leucantha, S. elegans ‘Scarlet Pineapple’. (2) Moderately heat resistant – L. x intermetia Provence, L. x heterophylla, L. stoechas; S. dorisiana. (3) Not heat resistant – L. angustifolia; S. officinalis, S. officinalis ‘Bergarrten’. For the administration of single chemical agent on lavender and sage to enhance the tolerance for high temperatures, different concentrations of salicylic acid (0,100,200, 400,800 μM) and calcium chloride (0,5,10,15 mM) were treated on lavender and sage before subjecting the plants to 55 ℃ continuous heat for 30 minutes to determine the heat tolerance of different varieties. The optimum concentration of salicylic acid administered to improve heat tolerance was 100μΜ for L. angustifolia, L. stoechas, L. pinnata, L. dentate; S. officinalis ‘Bergarrten’, S. elegans ‘Scarlet Pineapple’, S. officinalis, S. dorisiana, and S. leucantha. Applying 200 μΜ of salicylic acid enhanced the heat tolerance of sweet lavender, and Provence lavender. The optimum level of calcium chloride for enhancing heat tolerance was 5 mM for sweet lavender and S. Elegans scarlet Pineapple while 15mM was required for S. officinalis to achieve better ornamental quality and sustain reduced injuries under high temperature stress. For the administration of composite chemical agents on lavender and sage to enhance the tolerance for high temperatures, treatments of salicylic acid, calcium chloride, salicylic acid and calcium chloride complex agent were given to sweet lavender, sage and pineapple sage two hours before exposing the plants to high temperature stress of 55 ℃ continuous heat for 30 minutes. The result showed that composite chemicals had effectively enhanced heat tolerance more than other treatments of single chemical suggesting the cumulative benefit and cost savings that can be achieved from using a combination of salicylic acid and calcium chloride.