Y. Shahak¹, E.E. Gussakovsky¹, E. Shpiegel², E. Matan³, I. Dory³ and M. Oren-Shamir^1
1Institute of Horticulture, A.R.O. The Volcani Center, Bet-Dagan 50250, Israel;
²Extension Service, Ministry of Agriculture, Bet-Dagan 50250 Israel;
³Southern R&D, Bsor Experimental Station, Negev 85400, Israel.

Keywords: shade-nets, green-decorative branhces, cut-flowers, light spectrum.

Abstract:  Many green-decorative branches ("Greens") and cut flowers are commercially grown under plastic shade nets, for both the reduction of the natural intercepted sunlight as well as physical protection. The most commonly used are the black nets, which do not affect the visible light spectrum. We are studying the effects of shade nets of varying optical properties on the vegetative and flowering responses of ornamental plants, searching for nets which will specifically induce a desired behavior, thus gaining benefits in addition to the mere shading. Nets of different spectra of transmittance, light scattering, reflectance and thermal properties were studied for their effect on the vegetative growth of several Greens: Pittosporum variegatum, Ruscus hypoglossum, and Leather-leaf fern. The knitting densities of all nets under study have been adjusted to yield the same % shading in the PAR (photosynthetically active radiation) range of the spectrum. Experiments were carried out in commercial plots. Data were collected for microclimate, physiological and horticultural parameters. The main results obtained so far: (i) pronounced stimulation by the Red net; (ii) dwarfing by the Blue net; (iii) enhanced branching by the Grey net, yielding "bushy" plants with short side branches; (iv) the reflective, thermal net (Aluminet^R) enhanced long branching (in Pittosporum).  Application of a similar approach to cut flowers (e.g. Lupinus luteus, Lisianthus eustoma, Dubium ornitugalum) yielded dramatic effects of several nets on both vegetative and flowering behavior. The results to be presented suggest that sophistication of the use of shade nets can lead to better agricultural performance.

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