Effect of the Difference between Photoperiod and Dark Period Temperatures, and Photosynthetic Photon Flux Density on the Shoot Length and Growth of Potato Plantlets In Vitro

Abstract

Potato plantlets (Solanum tuberosum L. cv. Benimaru) under CO₂ enriched and photoauto-trophic culture conditions were subjected to three different photo-/dark period temperature combinations (25°/15°C, 20°/20°C and 15°/25°C) and two levels of photosynthetic photon flux densities (74 and 147 μmol-m ^-2.sec^-1). The shoot length of the plantlets under the same photosytnthetic photon flux density (PPF) was reduced with decreasing the difference between photoperiod and dark period temperatures (it is named DIF, photoperiod temperature minus dark period temperature). No marked differences in the fresh and dry weights per plantlet were observed among the three DIF treatments in each PPF treatment. The higher PPF led to a decrease in the shoot length, an increase in the fresh weight, dry weight and leaf area per plantlet in each DIF treatment. It is suggested that shoot length of plantlets in vitro under CO₂ enriched and photoautotrophic culture conditions can be controlled without reducing the weight increments and leaf area per plantlet by regulating the difference between photoperiod and dark period temperatures.