Rapid Acclimatization of Eucalyptus Plantlets by Controlling Photosynthetic Photon Flux Density and Relative Humidity.

Abstract

Eucalyptus camaldulensis shoots were cultured in vitro photoautotrophically for 21 days. Plantlets in vitro were transferred for one-day acclimatization ex vitro under the conditions of 10, 100 or 1000 μmol m-2 s-1 photosynthetic photon flux density (PPFD) combined with 55±5 or 85±5% relative humidity. Then, plantlets from each acclimatization condition were transplanted and cultured ex vitro for 13 days at 1000 μmol m-2 s-1 PPFD, 55% relative humidity and 35°C air temperature. One-day acclimatization ex vitro under either the high PPFD with high relative humidity or low PPFD with low relative humidity reduced the extent of leaf damage and chlorophyll damage. These resulted in high net photosynthetic rate and consequently contributed to high growth rates and high survival percentage of plantlets after ex vitro culture.