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 thiosulphate--Ag2S2O3 as inhibitors of ethylene activity, cobalt chloride--CoCl2 as inhibitor of ethylene biosynthesis) and ethylene stimulator (aminocyclopropane-1-carboxylic acid--ACC) were studied on the growth of cauliflower (Brassica oleracea L.) seedlings cultured in closed vessels (60 cm3). The addition of ethylene inhibitors have significant stimulatory effects on the growth and development of seedlings and the effects were greatest with 10 micromolar 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 ventilation (humidity-induced convective through-flow ventilation, diffusive ventilation and sealed condition) on the growth and physiology of in vitro cauliflower seedlings were also investigated. The seedlings were cultured either in the presence or absence of AgNO3 (inhibitors of ethylene activity) and ACC (a precursor). Ethylene and CO2 levels in the head-space of the culture vessels were monitored. The humidity-induced through-flow ventilation system has shown to be effective for improving growth, leaf chlorophyll content and the rate of net photosynthesis and preventing symptoms of hyperhydricity, such as leaf epinasty, and franginess, reduction of leaf area etc. In contrast, the results also indicated that the sealing of culture vessels could have serious inhibitory effects on growth and development, induce hyperhydricity and reduce leaf chlorophyll content. In the light period, CO2 depletion occurred in the head-space of the sealed vessels (ca. 40 microliter l-1), the CO2 concentration increased with increasing efficiency of the ventilation. No ethylene accumulation was noticed in the head-space of the culture vessels when humidity-induced throughflow ventilation was applied: however, high ethylene accumulation occurred in sealed vessels.