Effects of colored shade netting on the vegetative development and on the photosynthetic activity in several Hydrangea genotypes.

摘要

Hydrangea (Hydrangeaceae) is an ornamental plant for garden decoration and as potted plant, and also for cut flower production. It blooms from early spring to late autumn with an inflorescence at the end of the stems. In general, light needs of Hydrangea plants depend on the variety. Some Hydrangea's tolerate more light than others, which need a total or partial shadow position: excessive light can bleach or scorch flowers and droop leaves. Under Italian climatic conditions, most of them need shading. For this, the effects of several colored nets on shoot elongation, branching and flowering in ornamentals, were studied. Plants belonging to different cultivars were arranged under 70% shading of blue, red and black nets, and then the effect of spectral control of light on physiology and vegetative development was evaluated. Light measurements were carried out, to monitor the light conditions which the plants were exposed to. Spectra of the total solar light were measured under each net by a spectroradiometer. These data were further processed to calculate the transmittance spectra, as well as UV-A/PAR and Red/Far Red ratio. During the growing season data were collected from six plants for each genotype, under different colored nets; photosynthesis, CO₂ internal content, transpiration rate and stomatal conductance were measured by a portable porometer type CIRAS-2, leaf area index (LAI) by a ceptometer PAR/LAI LP-80 and leaves variegation (only H. macrophylla 'Lemon Wave' and 'Tricolor') by WinDIAS Image Analysis System (Delta-T Devices, U.K.).