Combined foliar-applied L-glutamic acid, nitrogen, and potassium improve plant growth, physio-chemical attributes, minerals, and longevity of gerbera (Gerbera jamesonii)

Abstract

Foliar application of amino acids and nutrients is an effective practice to improve plant yield in agriculture and horticulture. The hydroponic experiment was carried out to find the changes in physiological attributes, antioxidant enzymes activity, minerals, and flower number and longevity of gerbera (Gerbera jamesonii) plants under foliar application of L-glutamic acid (GA), potassium (K), and nitrogen (N). Plant fresh weight under 4 and 8 g L−1 GA was higher than other experimental treatments. The main improvement of flower number was related to 5 g L−1 K. Lignification in plants treated with non-GA/N and 5 g L−1 K was higher compared to other experimental treatments. Relative water content (RWC) and total soluble sugar (TSS) in plants sprayed with 8 g L−1 GA and 5 g L−1 N and K were greater than other experiment plans. The activities of phenylalanine ammonia-lyase (PAL), catalase (CAT), superoxide dismutase (SOD) increased by progressing GA, N, and K application. The highest leaf P was observed in 4 g L−1 GA with no foliar-applied K and N. Leaf N increased with enhancing GA and N, in which its highest amount was found in plants experiencing 8 g L−1, 4 g L−1 N, and 5 g L−1. Besides, the concentration of K increased by advancing the foliar-applied GA, N, and K, particularly K levels. The maximum flower longevity, as an important trait, increased with 8 g L−1, 10 g L−1 N, and 5 g L−1 K. The present study suggests high concentration of GA in combination with high N and medium K to achieve the optimum plant quantity and quality in gerbera. Heat map analysis showed two distinguished clusters by GA and N through an effective role of SOD, TSS, PAL, and CAT in distinguishing the GA-based clusters and TSS, flower number, and P for N-based clusters.