Silicon effects on growth acclimatization and stress tolerance of bioreactor cultured Ornithogalum dubium plants.

摘要

Scaling-up in liquid medium in bioreactors provided an efficient economic micropropagation system for bulb and corm plants. Continuous aeration and circulation in bioreactors effects plant function and morphogenesis. Abnormal structure and hyperhydricity can be alleviated by temporary immersion and short period treatments of growth retardants. Abnormal plant growth may also be due to the lack of Silicon (Si) in plastic or non-silicate glass containers, as well as due to the use of double distilled water. Silicon is not considered an essential plant element, yet it is accumulated by plant roots and transported to the stems and leaves. The addition of sodium silicate to Ornithogalum dubium in liquid MS medium containing 8.9 micro M BA and 0.54 micro M NAA in disposable pre-sterilized 1.5-L plastic bioreactors, was studied. The addition of 50-150 mg/L, which was found to be the effective range, to a bioreactor containing 1.2 L medium, increased the plant dry weight to fresh weight ratio. It improved leaf growth, epidermal tissue structure, cell wall percent of the total cell biomass and the chlorophyll content in the treated leaves. The addition to the medium, of 100 mg/L Si, reduced shoot malformation, and increased plant firmness and mechanical strength. Abnormal plant morphology in liquid medium is known to be associated with oxidative stress. Si reduced H₂O₂ level in the leaves of regenerated plants and lowered the activity of the enzymes ascorbate peroxidase (AP) ascorbate oxidase (AC) and glutathione reductase (GR). The possibility that in several in vitro culture systems the use of double distilled water and non-silicate containing glass or plastic containers may effect plant growth and structure due to the lack or low levels of Si, will be discussed.