International Journal of Plant & Soil Science

Periploca angustifolia as an endangered plant species were grown at Balouza Research Station (North Sinai, Egypt) during the period from November, 2016 to April, 2018 including three months seedling stage, two months transplanting and establishment stage, and 12 months plant old after establishment, one meter between seedlings within each row as well as the drip irrigation system. Using three irrigation levels; 160, 120 and 80 mm/year distributed constantly every 10 days for one year along to investigate vegetative parameters, hydrogen peroxide (H₂O₂), polyphenol oxidase (PPO), peroxidase (POD), total free amino acids (FAA), total phenols and soluble sugars. All vegetative parameters (plant height, number of branches, number of pods, leaves fresh and dry weight, soft branches fresh and dry weight, hard branches fresh and dry weight, and branches height mean attained the highest reading at 160mm/year irrigation amount. The three irrigation amounts did not induce a significant change in H₂O₂ concentration in both leaves and roots of P. angustifolia. The irrigation with 80mm/year induced the highest PPO activity in leaves and roots and the highest POD activity in leaves of P. angustifolia. Also, the lowest used irrigation amount stimulated the highest accumulation of FAA, total phenols and soluble sugars in the leaves.