THE EFFECT OF BORON ON THE MORPHOLOGICAL AND PHYSIOLOGICAL RESPONSES OF SUNFLOWER SEEDLINGS (HELIANTHUS ANNUUS L.)

Boron, an essential element for many organisms, has a unique role in plant metabolism. Boron plays a vital role in cell propagation, plant growth, photosynthesis and various metabolic pathways. Although there have been different studies on the effects of boron on the sunflower, the number of studies of the effect of boron on its antioxidant defense mechanism is limited. This study aimed to determine the effect of boron on the morphological (leaf area) and physiological (chlorophyll contents and SOD, CAT, GR, and APX enzymes) characteristics of sunflower (Helianthus annuus L.) plants during the seedling growth period. The study used 250 g of turf contained in 15 cm x 13 cm pots. For each boron dose, six pots were used, and five seeds were planted in each pot, which were pressed down after covering with 75 g turf, and 100 ml of water was used for the first irrigation of each pot. Seedlings, which emerged in about a week, were irrigated every two days for two weeks with 100 ml of water containing boron (Na2O5B2O3.10H(2)O) at different doses of 0 (control) and 0.5, 1.0, 1.5 and 2.0 mg 1(-1) per pot. The largest leaf areas (2nd and 3rd) were observed in the seedlings irrigated with water containing 1 mg 1(-1) of boron. Chlorophyll content (chlorophyll a, chlorophyll b and total chlorophyll) decreased with increasing boron doses (10.39%, 31.78% and 31.27%, respectively), whereas GR and CAT activities increased (0.1% and 49.46%), and SOD and APX activities decreased (18.18% and 0.07%) with increasing doses of boron.