Original Article | 2007, Vol.29, No.2, pp. 253-260
Factors affecting in vitro seed germination and shoot multiplication of a pitcher plant (Nepenthes mirabilis (Lour.) Druce)
Khemika Khompat, Wacharin Tokhao and Arak Jantasilp
pp. 253 - 260
Abstract
Mature seeds of a pitcher plant (Nepenthes mirabilis (Lour.) Druce) were cultured in liquid and solid MS medium (Murashige and Skoog, 1962) supplemented with BA (6-benzyladenine) at 1, 3 or 5 mg/l or with coconut water (20% v/v). The cultures were incubated under light and dark conditions. Seeds germinated only under light incubation and BA supplemented to both types of media, and solid medium with 3 mg/l BA resulted the highest seed germination (26%) with good development of seedlings. On the contrary, the addition of coconut water to the basal medium produced poor seed germination and seedling growth. Moreover, all cultures in liquid medium terminated their growth after 6 weeks of culture. Young seedlings were subsequently transferred to fresh media of the same treatments after 15 weeks of seed culture. Multiple shoots were proliferated in all levels of BA after 6 weeks of transferring and more shoots were produced as BA level was increased. However, at high BA level of 5 mg/l, rosetting of shoots occurred while lowering BA level to 3 mg/l, fewer shoots were produced but they were vigorous, larger shoots with complete leaves. Root development finally occurred in all BA treatments except the addition of coconut water. To evaluate the potential of shoot multiplication in different strengths of MS macromutrient, two types of explants, viz. shoot explants and stem explants (both approx. 1.5 cm long) from in vitro seedlings, were cultured on full-strength MS macronutrient medium, 1/2 MS, 1/4 MS and 1/8 MS medium. Following 16 weeks of culture, shoot production (number/ explant) increased in both explant types as the macronutrient strength decreased. However, when lowering to 1/8 MS, the fewest shoots were produced and exhibited nutrient deficiency of leaf chlorosis. The optimum strength of MS macronutrient for the maximum production of normal shoots with complete leaves was 1/2 MS medium while 1/4 MS medium produced the highest shoot number from stem explants but shoots were small with abnormal narrow leaf blade. In vitro pitcher development occurred spontaneously in all levels of MS macronutrient .
