The effect of drought stress and exogenous ascorbate on photosynthetic pigments, flavonoids, phenol compounds and lipid peroxidation in Pimpinella anisum L

Drought stress provokes ROS production in plant cell chloroplasts and subsequently causes lipid membrane peroxidation and damage. Pimpinella anisum L. is one of the aromatic herbal plants which has great export value. The aim of this study was applying exogenous ascorbate in order to control oxidative stress during drought tolerance. Changes of pigment content of leaves, total phenol compounds, malonedialdehyde (MDA) content were measured. In a pot study, drought stress introduced to treatments with 3 replicates based on 3 levels of field capacity (100, 60 and 25%) and ascorbate (1.4 mM) sprayed on them. Chlorophyll content and chlorophyll a/b ratio decreased with increasing in stress levels, while flavonoids and anthocyanins increased. Carotene and xanthophyll increased only in moderate stress level due to drought. Exogenous ascorbate increased chlorophylls and carotenoid content but decreased flavonoid and anthocyanin contents and had great effect on increasing phenol compound in all stress levels. MDA content remained relatively constant, but increased significantly in severe stress levels. Applying exogenous ascorbate led to decreasing metabolite. According to the results exogenous ascorbate could increase the ability of Pimpinella anisum in response to drought stress with different mechanisms and had protective effect against lipid peroxidation due to drought stress.