The localization of NADPH oxidase and reactive oxygen species in in vitro-cultured Mesembryanthemum crystallinum L. hypocotyls discloses their differing roles in rhizogenesis

This work demonstrated how reactive oxygen species (ROS) are involved in the regulation of rhizogenesis from hypocotyls of Mesembryanthemum crystallinum L. cultured on a medium containing 1-naphthaleneacetic acid (NAA). The increase of NADPH oxidase activity was correlated with an increase of hydrogen peroxide (H2O2) content and induction of mitotic activity in vascular cylinder cells, leading to root formation from cultured hypocotyls. Diphenylene iodonium (DPI), an inhibitor of NADPH oxidase, inhibited H2O2 production and blocked rhizogenesis. Ultrastructural studies revealed differences in H2O2 localization between the vascular cylinder cells and cortex parenchyma cells of cultured explants. We suggest that NADPH oxidase is responsible for H2O2 level regulation in vascular cylinder cells, while peroxidase (POD) participates in H2O2 level regulation in cortex cells. Blue formazan (NBT) precipitates indicating superoxide radical (O2 •−) accumulation were localized within the vascular cylinder cells during the early stages of rhizogenesis and at the tip of root primordia, as well as in the distal and middle parts of newly formed organs. 3,3′-diaminobenzidine (DAB) staining of H2O2 was more intense in vascular bundle cells and in cortex cells. In newly formed roots, H2O2 was localized in vascular tissue. Adding DPI to the medium led to a decrease in the intensity of NBT and DAB staining in cultured explants. Accumulation of O2 •− was then limited to epidermis cells, while H2O2 was accumulated only in vascular tissue. These results indicate that O2 •− is engaged in processes of rhizogenesis induction involving division of competent cells, while H2O2 is engaged in developmental processes mainly involving cell growth

Use of Water Hyacinth ( Eichhornia crassipes

This study was conducted to investigate the feasibility of using water hyacinth composted with (WHCM) and without (WHC) pig manure as a peat substitute in substrates for tomato seedling nursery and Chinese cabbage production. The main physical and chemical characteristics of substrates with 30% (S1), 50% (S2), and 60% (S3) WHC or with 30% WHCM (S4) were analyzed. The total porosity and air porosity of the substrates fell below the range for ideal substrates and tended to decrease with the increasing WHC proportions. Water holding capacity was significantly lower in S4 than in S1. Electrical conductivity levels were significantly raised by the compost additions, especially by WHCM addition. Substrates with 30%–60% WHC performed equally well in tomato seedling germination (92.0%–95.3%), while substrate with 30% WHCM gave a poor result (76.0%). The stem diameter, plant height, and biomass of tomato seedlings showed a trend of decrease with the increasing WHC proportions or with addition of WHCM in the substrates. The performance and quality of Chinese cabbage were generally reduced by addition of the composts in the order of S1 > S2 > S3 > S4. Growth parameters of the plants did not differ significantly between S1 and S2. These results suggested that the percentage of WCH in the substrates could be added up to 50% without apparently affecting the growth or product quality of Chinese cabbage.No Full Tex