14 research outputs found
The response of three Leucadendron cultivars (Proteaceae) to phosphorus levels
Abstract The objective of this study was to compare the growth of three Leucadendrons (Proteaceae) cultivars (`Safari Sunset',`Orot' and`Meir') fertigated with three levels of P. The plants were grown in tuff (pyroclastic material, characterized by high porosity) in 10 l pots and fertigated daily. The experiment included control treatment (plants irrigated with tap water) and three levels of P (0, 10 and 20 mg l À1 ), while N and K in the P-treatments were kept at a constant rate of 50 mg l À1 . Under P de®ciency, the development of`Orot' plants was signi®cantly superior to that of`Safari Sunset' and`Meir' cultivars, but as P application increased to 20 mg l À1 ,`Safari Sunset' growth was quite similar to that of`Orot'. The very low growth rate of`Meir', probably eliminates this cultivar as a potential rootstock for commercial purpose. The low sensitivity of`Orot' to nutrient application is a promising characteristic to avoid micro-nutrients de®ciency and a signi®cant advantage, especially under ®eld conditions. No symptoms of P toxicity were observed even at the highest P level (20 mg l À1 ), at any of the cultivars tested.
Transmission of Viroids and Viruses by Tissue Implantation and Transport across the Callus Barrier
Micrografting of Protea cynaroides
The inability to induce rooting of in vitro-established Protea cynaroides microshoots has prevented the production of complete plantlets. A successful shoot-tip micrografting technique was developed using in vitro-germinated P. cynaroides seedlings as rootstocks and axenic microshoots established from pot plants as microscions. Thirty-day old seedlings, germinated on growth-regulator-free, half-strength Murashige and Skoog medium, were decapitated and a vertical incision made from the top end. The bottom ends of microshoots established on modified Murashige and Skoog medium were cut into a wedge (‘V’) shape, and placed into the incision. The micrografted explants were cultured in a growth chamber with the temperature adjusted to 25 ± 2°C, with a 12-h photoperiod. Best results were obtained by placing the microscions directly onto the rootstock without any pre-treatments. Dipping the explants in anti-oxidant solution or placing a layer of medium around the graft area led to the blackening of the microscion.
Abbreviations EDTA Ethylenediaminetetraacetate - BAP 6-Benzylaminopurine - GA3 Gibberellic acid - PAR Photosynthetic active radiatio