Effect of biostimulants on chlorophyll fluorescence parameters of broccoli (Brassica oleracea var. italica) under drought stress and rewatering

The aim of the research was to determine the influence of biostimulants amino acids and amino acids + Ascophyllum nodosum filtrate on two broccoli cultivars ‘Agassi’ and ‘Tiburon’ and their response to soil drought. The plants were watered with Ascophyllum nodosum filtrate before planting and sprayed with amino acids after planting three times. Chlorophyll fluorescence measurements were performed before, during and after stress. They showed a considerable difference in cultivars’ response to stress, with ‘Agassi’ being more sensitive. Application of biostimulants enhanced the tolerance to drought stress. Maximum photochemical efficiency of PSII was unchanged, whereas the quantum yield of electron transport and photochemical fluorescence quenching values increased and the non-photochemical fluorescence quenching decreased. Moreover, the apparent photosynthetic electron transport rate rose. Chlorophyll content index was affected by the cultivar and application of biostimulants.