Effect of Biostimulants on Several Physiological Characteristics and Chlorophyll Content in Broccoli under Drought Stress and Re-watering

Abstract

Drought stress is one of the many factors that lead to decreased yield in both quality and quantity. One method to improve plant resistance to this stress is application of biostimulants. The most widely used biostimulants are protein hydrolysates, containing sea algae extract and humus compounds. In the present study, the influence of the amino acids as well as combination of amino acids with Ascophyllum nodosum filtrate on broccoli (Brassica oleracea var. italica) plants cvs. ‘Agassi’ and ‘Tiburon’ was investigated. The plants were watered with Ascophyllum nodosum filtrate three days before planting and sprayed three times with amino acids two, four and six weeks after planting. The present results show that biostimulants have a significant effect on both gas exchange and transpiration rate both prior to the application of stress, under drought stress and after re-watering. Biostimulant treatment led to an increase of drought tolerance in both studied cultivars but the final effect depended on cultivar. ‘Tiburon’ cultivar turned out to be more tolerant to drought stress than ‘Agassi’. The application of biostimulants resulted in an increase of photosynthetic rate, stomatal conductance, internal CO₂ concentration and transpiration rate in ‘Agassi’ cultivar under drought stress. This effect was not observed in ‘Tiburon’. The chlorophyll content was higher under drought stress as compared to the value prior to stress in both cultivars.