Effects of turgor potentials of epidermal cells neighbouring guard cells on stomatal opening in detached leaf epidermis and intact leaflets of Vicia faba L. (faba bean)

Leaflets of Vicia faba L. (faba bean) were used to determine whether the mechanical forces resulting from the turgor potentials (Φ_p) of the larger epidermal cells neighbouring guard cells play a significant role in regulating stomatal aperture. When Φ_p, of epidermis and Φ_p of bulk leaflet tissue were compared at midday, Φ_p of epidermis were only 15–25% those of bulk leaflet tissue at all but the most negative leaflet water potentials (Φ). When plants were bagged to increase Φ by reducing vapour pressure differences between leaflets and air, Φ_p of bulk leaflet tissue increased to predawn values, but Φ_p, of epidermis increased to only = 20% of predawn values and stomata opened to their widest apertures. Stomatal apertures were positively correlated with Φ_p of bulk leaflet tissue but they were not correlated with Φ_p of epidermis. Reductions in epidermal Φ_p, began predawn, before stomata were open, and reached minimum values at midday, when stomata were open. We conclude that, in Vicia faba, (1) reduction of Φ_p of epidermal cells begins predawn, reducing the counterforce to stomatal opening that would exist if full epidermal turgor were maintained throughout the day, and (2) changes in Φ_p, of leaf epidermal cells do not play a significant role in regulating stomatal aperture.     

The use of insecticides to control maize rough dwarf virus (MRDV) in maize*

Insecticides were screened in the laboratory for fast action against the delphacid planthopper, Laodelphax striatellus, the vector of maize rough dwarf virus (MRDV) in Israel. In these tests the synthetic pyrethroids were more efficient than oxydemeton-methyl or endosulfan giving 50% mortality after 5 h compared to 10% in the non-pyrethroid insecticides. Selected insecticides were then tested in maize fields for their effect on disease spread and crop yield. The synthetic pyrethroids cypermethrin, fluvalinate and biphenthrin reduced MRDV incidence by 22–59% and disease was less severe in the treated plots. Total crop yield (stems, leaves, ears) was 28% higher in the biphenthrin-and fluvalinate-treated plots than in untreated plots.     

Characterization of Glycogen and Amino Acid Pool of Entamoeba histolytica by 13C-NMR Spectroscopy

ABSTRACT. Trophozoite extracts of axenic Entamoeba histolytica were investigated by natural-abundance ¹³C-NMR spectroscopy. The extracts were found to contain a high level of glycogen (30 mM glucose equivalents), which had a compact structure as suggested by α (1 → 6) branch points every 5–6 glucose residues. As other major metabolites, we identified putrescine (9.5 mM) and the following free amino acids: tyrosine and phenylalanine (1 mM), glycine, lysine and methionine (2 mM), isoleucine (5 mM), proline and valine (6–7 mM), leucine (11 mM) and glutamate (22 mM). Glutamate and proline may serve, together with putrescine, as intracellular osmolytes.     

Seasonal prevalence of mosquitoes collected from light traps with notes on malaria in the Republic of Korea, 2004

Adult mosquito surveillance was conducted during 2004 at 29 US military installations and training sites located in six provinces in the Republic of Korea. Adult mosquitoes were collected in New Jersey light traps and Magnet traps from 1 May through 15 October to determine threshold levels to initiate pesticide applications and to identify malaria infection rates at selected army installations and training sites. A total of 89 206 adults (78 454 [87.9%] females and 10 752 [12.1%] males) comprising 20 species (including five members of the Anopheles Hyrcanus Group) and belonging to seven genera were collected. The most common species collected were members of Culex tritaeniorhynchus Giles (49.4%) and Anopheles sinensis Wiedemann complex (39.1%), followed by Culex pipiens Coquillett (6.1%) and Aedes vexans nipponii (Theobald) (4.2%). Trap indices varied widely for species over their range, due in part to geographical distribution and degree of association with urban communities.     

3H-THYMIDINE INCORPORATION INTO CELL NUCLEI IN GERMINATING LETTUCE SEEDS

Lettuce seeds were soaked in a ³H-thymidine solution and autoradiogramof sections of these seeds, fixed prior to and after germination(root protrusion), were prepared. Labeled nuclei in intact,punctured, as well as broken seeds began to appear approximatelyat the time of root protrusion. In the nuclei of the radicle,the beginning of ³H-thymidine incorporation precedes the divisionof nuclei by one to two hours, and all the dividing cells incorporate³H-thymidine before their first division. Occasional dividingcells in the epidermis of the hypocotyl were not found to be³H-labeled. In intact seeds, the nuclei observed in the coneof the plumule showed radioactivity approximately 3–4hr after germination, while in punctured and broken seeds the³H-incorporation occurred some hours earlier. (Received December 3, 1962; )     

The surface morphology of locust hindgut cuticle*

The surface architecture of hindgut cuticle in Locusta migratoria is described. Infundibulate pores are present in the midrectal pads, the ileum and the posterior rectum. It is suggested that they lead to canals traversing the cuticle. Larger occluded crater-like pores are present on the posterior rectal pads and may be glandular. The cuticle of the ileum and colon is invested with numerous spikes pointing backwards, and the interpad region of the rectum with upright spikes pointing inwards. These spikes probably serve to direct the faeces backwards from the ileum and colon, and to impale the faecal pellet during dehydration in the rectum.     

The initiation of growth in isolated lima bean axes. Physiological and fine structural effects of actinomycin D, cycloheximide and chloramphenicol.

Excised lima bean axes were germinated for 24 hr in water, variousconcentrations of CHI, CAP or actinomycin D. None of the inhibitorsaffected water uptake before onset of growth. Growth was completelyinhibited by CHI and CAP, but only partly by actinomycin D.Rate of ³H-leucine incorporation rose during the lag phase inwater uptake and increased further during growth. The incorporationwas inhibited by CAP and CHI at all stages, but by actinomycinD only during growth. Actinomycin D prevented developmentalfine structural changes. In CHI treated axes number of mitochondriaincreased, O₂2 uptake was reduced, and higher cytochrome oxidaseactivity induced. CAP caused changes in the appearance of proteinvacuoles, but apparently prevented loss of storage material.The relation between the physiological and structural effectsof the inhibitors is discussed. (Received June 13, 1970; )