THE INFLUENCE OF PLANT DENSITY AND GRADUAL SHADING ON VEGETATIVE GROWTH OF DENDRANTHEMA

Vegetative growth of Dendranthema x grandiflora (Ramat.) Kitam. ‘Casa’ was investigated at two plant densities and under three levels of shading for five weeks in a glasshouse.
The three shading regimes were: 1) 73% shading when outdoor irradiance was 200–500 Wm^-2 and 87% shading when outdoor irradiance was higher than 500 Wm^-2 (low/high). 2) 80% shading when outdoor irradiance was 200–500 Wm^-2 and 87% shading when outdoor irradiance was higher than 500 Wm^-2 (medium/high). 3) 87% shading when outdoor irradiance was higher than 200 Wm^-2 (high). Plants were grown at two densities in each of the three shading treatments, a high density with 125 plants per m² and a low density with 83 plants per m². By the use of gradual shading (shading in two steps) it was possible to increase the total accumulated photosynthetically active radiation, without increasing the maximum photon flux density to extremes in the glasshouse.
After four weeks, plants grown in the low/high shading regime were larger with respect to plant height, mean internode length and leaf area ratio than plants in the high shading regime.
After five weeks the differences were gone, except that plants in the low/high shading regime were taller and had longer internodes.
Plant density had a pronounced effect on plant growth.
Plants grown at low density were larger with respect to all measured parameters, except mean internode length.

II Workshop on Environmental Regulation of Plant Morphogenesis

A. Huld, N.E. Andersson

Leaf area index, leaf area ratio, light sum, red/far-red light

https://doi.org/10.17660/ActaHortic.1997.435.20