Evaluation of a closed system, diffusive and humidity-induced convective throughflow ventilation on the growth and physiology of cauliflower in vitro

The effects of ethylene inhibitors (silver nitrate - AgNO3 and silver thios ulphate - Ag2S2O3 as inhibitors of ethylene activity, cobalt chloride - CoC l2 as inhibitor of ethylene biosynthesis) and ethylene stimulator (aminocyc lopropane-1-carboxylic acid - ACC) were studied on the growth of cauliflowe r (Brassica oleracea L.) seedlings cultured in closed vessels (60 cm(3)). T he addition of ethylene inhibitors have significant stimulatory effects on the growth and development of seedlings and the effects were greatest with 10 mu M AgNO3, the fresh weight of leaves was 2.6x, and the leaf area 2.8x those of the control (no additives). The effects of various methods of vent ilation (humidity-induced convective through-flow ventilation, diffusive ve ntilation and sealed condition) on the growth and physiology of in vitro ca uliflower seedlings were also investigated. The seedlings were cultured eit her in the presence or absence of AgNO3 (inhibitors of ethylene activity) a nd ACC (a precursor). Ethylene and CO2 levels in the head-space of the cult ure vessels were monitored. The humidity-induced through-flow ventilation s ystem has shown to be effective for improving growth, leaf chlorophyll cont ent and the rate of net photosynthesis and preventing symptoms of hyperhydr icity, such as leaf epinasty, and franginess, reduction of leaf area etc. I n contrast, the results also indicated that the sealing of culture vessels could have serious inhibitory effects on growth and development, induce hyp erhydricity and reduce leaf chlorophyll content. In the light period, CO2 depletion occurred in the head-space of the sealed vessels (ca. 40 mu l l(-1)), the CO2 concentration increased with increasi ng efficiency of the ventilation. No ethylene accumulation was noticed in t he head-space of the culture vessels when humidity-induced throughflow vent ilation was applied; however, high ethylene accumulation occurred in sealed vessels.