Effect of different cultural conditions on micropropagation of rose (Rosa sp. L.) and globe artichoke (Cynara scolymus L.)

The objective of the present study was to investigate the influence of different cultural conditions in the multiplication, rooting and acclimatization phases on the growth of rose and globe artichoke and their effects on the subsequent micropropagation phases. The growth of rose plants in vitro was affected by the type of gelling agent added to the culture medium. The best results concerning plant growth were found by using agar as gelling agent at the concentration of 6 g L-1. On the other hand, the use of gelrite as gelling agent in the culture medium cannot be recommended for the micropropagation of rose cvs. ‘Frisco’ and ‘Lambada’, as well as the liquid medium in rose cv. ‘Kardinal’. Moreover, explants grown at 0.1 mg L-1 of NAA (auxin) in the rooting phase presented better growth and higher survival rate in the acclimatization phase when compared to explants grown at 0.5 mg L-1, as well as at 10 g L-1 sucrose in comparison to 20 or 40 L-1. The type of closure used also played an important role in the rooting phase. The use of glass, steristop or aluminium as closure showed better results than plastic film for growth of shoots for all tested cultivars (‘Frisco’, ‘Kardinal’ and ‘Lambada’). In addition, the growth of ‘Kardinal’ was not influenced by the use of Magenta B-CAP covers with or without filter in baby food culture jars. Temperature in the rooting phase clearly influenced rooting formation. The formation of roots was improved at 16°C, whereas shoot growth showed better results at higher temperatures (20°C or 24°C), being different temperatures required for the optimum growth of roots and shoots. Additionally, a minimum duration of the rooting phase of five weeks should be used in the micropropagation of rose. Substrates with higher drainage capacity in the initial phase of acclimatization (as e.g. a mixture of peat and perlite in the proportion 1peat:3perlite v/v) increased the survival rate of plants. The use of perlite mixed with peat should be recommended in order to increase the looseness, permeability and aeration of the substrate. The growth of globe artichoke cv. ‘Green globe’ plants in vitro was affected by the type and concentration of growth regulators supplemented to the culture medium. The use of 2.0 mg L-1 NAA + 2.0 mg L-1 BA in the culture medium positively influenced the growth of shoots in the multiplication phase. However, in the subsequent phases (rooting and acclimatization) this effect was not maintained. In these phases, higher shoot development, rooting percentage, and lower mortality rate of plants were found with 0.2 mg L-1 NAA + 0.2 mg L-1 BA or with 2.0 mg L-1 NAA + 2.0 mg L-1 Kinetin in the multiplication phase. Concerning the rooting phase, the addition of auxin (NAA) to the rooting medium at a concentration of 0.5 mg L-1 is suitable for the micropropagation of globe artichoke. Moreover, the supplementation of the rooting medium with gibberellic acid (GA3) is not beneficial. Light intensity of 110 mmol m-2 s-1 can be used for the micropropagation of globe artichoke, since plants were not photoinhibited under this condition. Lower values of the Fv/Fm ratio may indicate the occurrence of photoinhibition due to damage to photosystem II reaction centers in response to light intensity of 210 mmol m-2 s-1. The results indicate that a reduction of sucrose concentration is advantageous for the micropropagation of globe artichoke.