Effect of Relative Humidity in the Culture Vessel on the Growth and Shoot Elongation of Potato (Solanum tuberosum L.) Plantlets In Vitro.

Abstract

An experiment was conducted to investigate the effect of relative humidity (RH) in the culture vessel on the growth of potato plantlets In Vitro, especially on shoot elongation. Plantlets were cultured under four RH conditions obtained by using distilled water or different salt-saturated solutions. Culture vessels had number of air exchanges per hour of 0.95. The vessels containing the cultures were maintained in a culture room at 25°C and 75% RH under 16 hr•day-1 photoperiod with 100 μmol • m-2 • sec-1 photo-synthetic photon flux density. The CO2 concentration in the culture room was increased with time from 550 to 1400 μmol mol-1 to maintain the concentration in the vessel at or above 350 μmol • mol-1.The actual measured RH in the vessel increased in all treatments except for the control with time as the explants grew into the plantlets, which decreased the differences in RH among the treatments. The shoot length of plantlets decreased with decreasing the initial (day 8) RH. The shortest shoot length, 35mm, was observed in the lowest RH treatment and the longest one, 52 mm, in the control. There were no significant differences in dry weight per plantlet among the treatments. Short and vigorous micropropagated transplants could be obtained by the slight reduction in RH without a significant reduction in dry weight of plantlets.