In vitro aerial environments and their effects on growth and development of plants

In this chapter, general characteristics of in vitro aerial environment and fundamental features of major environmental factors in photoautotrophic and conventional (photomixotrophic or heterotrophic) micropropagation are summarized and compared with the general characteristics of the greenhouse environment for plant propagation and transplant production. Effects of the number of air exchanges of the vessel on CO₂ concentration, C₂H ₄ concentration and relative humidity in the vessel are also discussed. It is pointed out that the in vitro environment is considerably different from the greenhouse environment. Basic physical relationships governing the in vitro environment are introduced to facilitate understanding of the mechanism of in vitro environment and to indicate opportunities to improve the in vitro environment for photoautotrophic micropropagation. Basic ideas came from our observation that, in many cases, germinated seeds with cotyledons and stem cuttings with a leaf grow and develop faster in the controlled environment greenhouse than in the culture vessel in conventional micropropagation. Effects of environmental factors on the growth and development of plantlets in vitro are also discussed.