Shading stock plants with photoselective nets affects the yield and rooting quality of their cuttings
Nissim-Levi, A.; Ovadia, R.; Kagan, S.; Oren-Shamir, M.
Journal of Horticultural Science and Biotechnology 89(6): 693-699
Reducing light levels, decreasing the red to far-red (R:FR) light ratio, and exposing stock plants to blue light have been shown to increase the rooting potential of cuttings in various species. Here, we tested the effects of growing stock plants under photoselective shade nets, altering the spectrum of transmitted sunlight, and/or enriching the relative level of scattered light, on the yield and rooting quality of cuttings. Three ornamental plants, Pelargonium (including three cultivars, 'Isabel', 'Alara' and 'De Capo'), Laurus nobilis, and Heteromelis normally propagated by rooting cuttings, were chosen for this study. The nets chosen were a black neutral net and pearl, blue, or yellow photoselective nets. In Heteromelis, the pearl net caused a significant increase in the number of rooted cuttings per plant, but had no effect on the number of rooted cuttings in Pelargonium or L. nobilis stock plants. Instead, significant increases in cutting yields in all three Pelargonium cultivars and in L. nobilis were observed under the yellow net. The three photoselective nets also differed in their effects on rooting among the different species tested. None of the three photoselective nets decreased the rooting percentage or the frequency of rooting compared to the black net, in any experiment. Both the yellow and blue nets increased the rate at which the Pelargonium cuttings rooted. The yellow shade net had a double effect on all three Pelargonium cultivars, increasing the yield of cuttings per plant and also increasing their rate of rooting. In the two woody species, L. nobilis and Heteromelis, cuttings from stock plants grown under the pearl net rooted more efficiently compared to those from plants grown under the black net. Both the pearl and the blue nets increased the rooting efficiency in Heteromelis.