Effect of calcium nitrate foliar spray on the calcium content, growth and freezing tolerance of Forsythia × Intermedia cultivars

Abstract

In many northern regions frost hardiness of new cultivars of woody plants and perennials is fundamental for nursery production and the greenery industry. This study was conducted to determine the effect of calcium fertilization on frost resistance of Forsythia sp. cultivars. Plants were sprayed five times at four week intervals with calcium nitrate 1 g of (Ca(NO₃)₂). 100 ml H₂O⁻¹ per shrub. Shoots were frozen at three temperatures: –20, –25, and –30 °C. In all cases the chlorophyll content index in the leaves, and the calcium (Ca²⁺) content in leaves and stems of forsythia cultivars were significantly higher when calcium nitrate supplementation was provided. The Ca²⁺content in the roots was not affected. The freezing temperature had a great effect on the stem frost damage of tested forsythia cultivars. The greatest damage was observed after freezing at –30 °C. However, tissue damage of plants that were sprayed with calcium nitrate was considerably less evident, and cross sections of stems looked significantly better. At the lowest temperatures (–25 and –30 °C) a positive effect of calcium fertilization on lower electrolyte leakage was observed in all tested cultivars. Fertilization with finely ground calcium nitrate increased stem freezing tolerance of forsythia tested cultivars, especially new ones which have stems that are more susceptible to frost damage.

Keywords:

• calcium fertilizing
• cold acclimation
• freezing injury
• ornamental shrubs

Acknowledgments

The present research was supported by the Polish Ministry of Science and Higher Education as part of the statutory activities of the Research Institute of Horticulture.