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 μM AgNO₃, the fresh weight of leaves was 2.6×, and the leaf area 2.8× 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 vitrocauliflower 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 μl 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. This revised version was published online in June 2006 with corrections to the Cover Date.     

The cardiac neural crest in Ambystoma mexicanum.

To establish whether a region of the cranial neural crest contributes cells to the developing heart of Ambystoma mexicanum (axolotl), as it does in many other vertebrates, we constructed a fate map for the neural crest in late neurula stage (stage 19-20) embryos. The fluorescent vital dye, Dil, was used as the lineage label. The various regions of the cranial neural folds were identified in relation to such landmarks as the developing forebrain, midbrain and hindbrain, and the appearance and extent of emerging somites. Labelled cells originating in the rhombencephalic region were found in the aortic arches and in the truncus arteriosus, and occasionally in the walls of the conus arteriosus. Cells were also found in the third and fourth branchial arches. Labelled neural crest from the adjacent anterior trunk region appeared neither in the heart nor the visceral skeleton, whereas those from the mesencephalic region contributed to the first hypobranchial cartilage and to the first three branchial arches, but not to the heart. No labelled cells from any of the regions were seen in the ventricle or auricle.