Estimating Cuticle Resistance of Seedling Shoot Tips Based on the Penman-Monteith Model

Abstract

Morphological characteristics of seedlings such as height and size uniformity are important requirements in transplant production and are affected by temperature at the plant shoot-tip. Plant temperature is described by the energy budget equation based on the Penman-Monteith model. The energy budget equation of a plant shoot-tip consists of environmental factors and the shoot-tip cuticle resistance. The energy budget equation was algebraically modified to an equation that expresses the relationship between Vapor Pressure Deficit (VPD) and ambient air temperature (T_air) — plant shoot-tip temperature (T_p). This same relationship was also obtained by a simple experiment where VPD was regulated at constant T_air. Comparing the coefficient of these two equations, the cuticle resistance of plant shoot-tips was calculated. The experiments were conducted using Campanula ‘Birch Hybrid’, Campanula carpatica ‘Blue Clips’, and Geranium dalmaticum. The values of cuticle resistance of each plant are 524.9, 157.2 and 57.8 s/m, respectively.