Effect of growth regulators on mechanical properties of strelitzia leaves

A study was performed on the effect of strelitzia leaves spraying with ethephon at concentrations of 500, 1 000, 2 000, 4 000 mg dm-3 and with GA3 at concentrations of 100, 200, 400, 800 mg dm-3 on their postharvest quality and mechanical properties. One year old plants were sprayed with the preparations in March and April for three consecutive years. Leaves grown during that period were cut and their morphological features and mechanical properties were determined with the help of the following apparatus: INSTRON 6022, AREA METER Delta – T Devices Ltd., DYNSTAT. It was found that application of GA3 – 800 mg dm-3 caused elongation of the leaf petiole and lamina by more than 100 and 40%, respectively, as well as an increase in petiole diameter. Elongated leaves were characterized by higher values of mechanical properties, which indicates their greater resistance to deformation and damage. GA3 caused the occurrence of the highest values of maximum stress during petiole bending in static test, and the highest strain and energy in measurements made on the lamina. Leaves treated with ethephon at concentrations of 1 000 and 2 000 mg dm-3 were characterized by higher values of petiole and whole lamina deformations. In dynamic tests, the energy appearing in petiole shearing was the greatest for leaves sprayed with GA3. Higher energy values were characteristic of petiole under the leaf sheath with relation to that at the lamina base. In the course of static tests performed for the lamina, higher values of maximum force, deformation and energy were recorded for leaves with whole lamina compared to those with the lamina partially removed.