Silica nanoparticles and calcium on the histological characteristics and stem bending in gerbera cut flower

Silica nanoparticles and calcium are necessary for improving plant yield and decreasing stem bending in gerbera flower (Gerbera Jamesonii L.). In order to determine the optimal concentrations of silica nanoparticles and calcium in gerberas (Gerbera Jamesonii L.), a factorial experiment in the form of completely randomized design with two factors was conducted. The first factor was the concentration of silica nanoparticles (Nanoparticle-SiO2) at four rates (0, 20, 40, and 80 mg L-1) and the second factor was the concentration of calcium chelate (Ca-Chelate) at four rates (0, 60, 120, and 240 mg L-1) which were applied as nutrient solutions. After harvest, characteristics such as stem bending, cellulose content, phenyl alanine ammonia-lyase enzyme activity in leaves, and stem histological characteristics were measured. Results indicated that the lowest stem bending (deviation angle of 8.78°) was observed with applying 20 mg L-1 Nanoparticle-SiO2 and 240 mg L-1 Ca-Chelate. Comparing with control, applying 80 mg L-1 Nanoparticle-SiO2 and 240 mg L-1 Ca-Chelate increased lignin and cellulose contents by 33 and 15%, respectively. The highest amount of phenylalanine ammonia-lyase (2.87 units per mg of fresh leaf) was obtained by using 60 mg L-1 calcium chelate. According to nutrient concentrations, the change patterns of xylem and stem lignification were different, which is in line with the results of the physiological studies conducted on the effects of applying silica nanoparticle and calcium in nutrient solution. Under the epidermis, there was a hypodermis (sclerenchyma) which strengthens stem tissue. Silica nanoparticles and calcium chelate due to increasing phenylalanine ammonia-lyase content and its effect on the production cycles of cellulose and lignin and increasing stem sclerenchyma, led to stems strength and lignification, which eventually decreased stem bending. According to study results, applying 40 mg L-1 Nanoparticle-SiO2 and 60 mg L-1 Ca-Chelate in hydroponic nutrient solution is recommended for growing gerbera flowers.