Summary: Phytotoxicity of a homologous series of sulphoberaine surfactants, 3‐(alkyldimethyl‐ammonio)‐1‐propanesulphonates, on Brassocattleya orchids increased with increasing alkyl chain length from eight to 14 carbon atoms of the lipophile, levelled off and then declined with the 18 carbon derivative. Because of its high Krafft point the tatter had reduced solubility at the assay temperature. Interfacial tensions of the nutrient solutions, measured against a test lipid, declined m parallel with the observed phytotoxicity. This and previous findings strongly support the suggestion that disruption of cellular membranes by surface active agents plays a key role in their toxicity.

Evidence obtained from incubation of corn (Zea mays cv. Golden Bantam) seedlings in dl-[benzene ring-U-(14)C]tryptophan, l-[5-(3)H]tryptophan, l-[U-(14)C]aspartate and [U-(14)C]glycerol indicates that niacin is synthesized in these plants via oxidative degradation of tryptophan. Aspartate and glycerol do not appear to be precursors of niacin in corn seedlings.

Rhizoctonia repens M 32, a mycorrhizal isolate from Orchis militaris requires both a carbohydrate (glucose or sucrose) and an amino acid (aspartic acid, glycine, serine, or glutamic acid) for growth. The fungus does not require an exogenous supply of vitamins in vitro. © 1975 Dr. W. Junk bv - Publishers.

Salinity tolerant taro tissues were selected and cultured in vitro on saline media (50-350 mOsm). Salt tolerance in these tissues was associated with increased levels of calcium oxalate, chlorophyll, protein and some secondary alkaloids. The concentration of other secondary alkaloids as well as the levels of quaternary alkaloids decreased. Calcium, potassium, magnesium and sodium content of the tissues decreased with increased salinity. These findings are discussed in relation to salinity tolerance in taro. © 1989.

Summary: Leaf‐tips of Epidendrum and Laeliocattleya (Orchidaceae) have been cultured in vitro. Epidendrum seedling leaf‐tips form calli on Murashige‐Skoog medium (MS) or after being transferred to Knudson C agar following prior growth on MS. Plantlets also develop from tips of young leaves of mature Laeliocattleya plants cultured in Heller's medium or in a solution specifically devised for orchid shoot‐tip cultures. In Heller's medium plantlet development is preceded by callus formation whereas in the shoot‐tip medium protocorm‐like bodies are formed first. These tissues when subcultured from Heller's medium or the shoot‐tip solution to Knudson C agar also produce plantlets which resemble orchid seedlings. The results are discussed in relation to the components of each medium, the requirements of germinating orchid seeds and protocorms, and the difficulties encountered in attempts to culture tissues of mono‐cotyledonous plants.

The structure of hircinol, a phytoalexin isolated from Loroglossum hircinum has been established as 2, 5-dihydroxy-4-methoxy-9,10-dihydrophenanthrene. This phytoalexin, the second to be identified in the Orchidaceae, is less effective than orchinol, and its isomeric co-metabolite, loroglossol, 5-hydroxy-2,4-dimethyoxy-9,10-dihydrophenanthrene, is inactive. © 1973.

SUMMARY: Orchid aerial roots contained chlorophylls and were shown to be capable of photosynthesis. 14CO2 feeding in the light showed that the C3 pathway was operating during the day. Aerial roots also exhibited diurnal acidity fluctuations typical of crassulacean acid metabolism (CAM) and malate was the only labelled compound isolated after night 14CO2 feeding. CO2 exchange patterns in aerial roots were consistent with CAM CO., fixation during the night hours. The rate of photosynthetic CO., fixation in the light was much greater than the rate of CAM CO2 fixation in the night. Measurements of CO2 exchange, however, showed little or no net uptake indicating that these roots were not completely autotrophic.