Cryopreservation of the anaerobic rumen fungus Neocallimastix patriciarum

A rapid extraction and purification procedure is described for the preparation of toxic peptides from freshwater blooms and laboratory isolates of Microcystis aeruginosa . Extraction with methanol/butanol, followed by C₁₈ cartridge concentration; gel filtration and high performance liquid chromatography yields discrete toxin peaks. Elution profiles for the laboratory isolates and bloom extracts are compared and the applicability of the method for detecting cyanobacterial toxins in natural waters is discussed.     

TOPICAL APPLICATION OF MOBILE LIQUIDS TO INSECTS BY MEANS OF MICRO-CAPILLARY TUBES

A method is described for topical application of mobile liquids, whether volatile or not, to insects. The principle is that of the self-filling micro-pipette, the 'pipettes' being calibrated lengths of fine, thin-walled glass capillary tube; for use a micro-capillary tube is mounted in a special holder. The doses delivered were shown to be adequately reproducible for mean doses of 0.03 μl. upwards. Precautions in use are: (1) in filling the capillary, its tip is dipped into the reservoir of liquid no more deeply than is necessary: (2) the dose is applied to the insect in such a way that the liquid is carried rapidly away from the delivery tip; and (3) pressure for expulsion of the dose from the capillary is maintained until after the delivery tip is removed from the insect.
A convenient apparatus for keeping a batch of insects under anaesthesia during their dosage is described.     

Input-output relation in a flexor reflex

Observations have been made upon a typical flexor reflex with the aim of disclosing the changes in amount, latency, and temporal configuration of reflex discharge that take place as afferent input is varied from zero to maximal for the band of cutaneous myelinated afferent fibers that extends upward from approximately 6 µ in diameter (group II fibers). Reflex threshold is reached at 6 to 12 per cent maximal afferent input. From threshold to maximal input the relation between input and amount of output is essentially linear, latency on the average decreases, the shorter central paths in general gain preference, but the known minimum pathway, one of three neurons, does not transmit unless aided by convergent activity. Flexor reflex discharge may occur in several bursts suggesting the existence of closed chain connections in the internuncial pools of the spinal cord. At any given input there is, in successively elicited reflexes, little correlation between latency and amount of discharge, at first sight a surprising result for each variable can be taken as a measure of excitability status of the motoneuron population. However, latency of discharge indicates excitability at the beginning of the reflex event whereas amount of discharge is an expression of excitability over the entire period of discharge. Given a constantly and rapidly fluctuating excitability absence of correlation between these variables would be an anticipated result.     

Sexual Dimorphism in Cirsium arvense (L.) Scop

Differences between males and females of Cirsium arvense (L.)Scop. in morphology and sexual performance are described. Nofunctional pollen was observed in females, and no pollen-sterileanthers were observed in males. The difference between the sexesin ovule functions is not absolute however: some males produceoccasional fruits. The number and distribution of fruits onboth sexes are described. The fruits borne on males are smallerand germinate less well than those borne on females, but theseedlings from the two sexes grow equally well. On the average,males contribute only 5.3 x 10^–4 as many genomes via ovulesas do females. The average male constancy, the proportion ofmale genes transmitted via pollen, is estimated as 0.9989. Theprimary sex index, a measure of the functional approach to strictdioecy (represented as 1.00) is 0.9995. C. arvense is describedas near-dioecious and varying from dioecy in a gynodioeciousmanner. The opinion expressed by Correns that the near-dioecyof C. arvense has been derived from hermaphroditism via gynodioecyis upheld.     

Co‐limitation of photosynthetic capacity by nitrogen and phosphorus in West Africa woodlands

Photosynthetic leaf traits were determined for savanna and forest ecosystems in West Africa, spanning a large range in precipitation. Standardized major axis fits revealed important differences between our data and reported global relationships. Especially for sites in the drier areas, plants showed higher photosynthetic rates for a given N or P when compared with relationships from the global data set. The best multiple regression for the pooled data set estimated V_cmax and J_max from N_DW and S. However, the best regression for different vegetation types varied, suggesting that the scaling of photosynthesis with leaf traits changed with vegetation types. A new model is presented representing independent constraints by N and P on photosynthesis, which can be evaluated with or without interactions with S. It assumes that limitation of photosynthesis will result from the least abundant nutrient, thereby being less sensitive to the allocation of the non‐limiting nutrient to non‐photosynthetic pools. The model predicts an optimum proportionality for N and P, which is distinct for V_cmax and J_max and inversely proportional to S. Initial tests showed the model to predict V_cmax and J_max successfully for other tropical forests characterized by a range of different foliar N and P concentrations.