Hormones and Apical Dominance in the Fern Davallia

Lateral buds of the fern Davallia trichomanoides are releasedfrom inhibition by the removal of the main shoot apex. However,auxin is not capable of substituting for the apex in decapitatedshoots nor can auxin in shoot tips be detected by bioassay orextraction and chromatography. Expanding leaves of this speciescontain auxin, but these organs are not responsible for inhibitionof lateral bud growth. The response of lateral buds to an exogenouslyapplied cytokinin does not result in initial bud break. It isconcluded that the hormonal factors known to govern apical dominancein seed plants are not responsible for the regulation of differentialbud expansion in this fern.     

Race specific resistance to lettuce downy mildew (Bremia lactucae) in the lettuce cultivar Bourguignonne Grosse Blonde d'Hiver

A stock of lettuce cv. Bourguignonne Grosse Blonde d'Hiver used in previous studies was shown to carry the race specific resistance factor R1 and not R9 as originally thought. Investigations into a commercial stock of cv. Bourguignonne which exhibited a heterogeneous reaction to some B. lactucae isolates showed that it was a mixture of two lines. Each line carried one of two R-factors (referred to as R9A and R9B) in a homozygous condition, although their identification was made difficult by the presence of R5/8. No plants were found which carried both R9A and R9B.     

Accumulation and subcellular distribution of cations in relation to the growth of potassium-deficient barley

Abstract Growth of barley (Hordeum vulgare L., cv. Georgie) was insensitive to soil K content above about 150 mg kg^?1, but at lower levels it declined. The reduction in yield was greater in soils containing approximately 10 mg Na kg^?1 than in soils with about 90 mg kg^?1 of Na. Growth was unaffected by changes in shoot K concentration above 75 mol m^?3, but declined at lower concentrations, and the decrease was less in plants grown in soils with high Na. Growth responses were not simply related to tissue K concentrations because plants grown in soils with extra Na had higher yields but lower K concentrations. When soil Na was low, plants accumulated Ca as tissue K declined, but when Na was provided this ion was accumulated. Plant Mg concentrations were generally low but increased as K decreased. The Ca and Mg were osmotically active. There were highly significant inverse linear relationships between yield and either the Ca or Mg concentrations in the shoots. X-ray microanalysis was used to examine the compartmentation of cations in leaves from barley plants (cv. Clipper) grown in nutrient solutions with high and low K concentrations. In plants grown with 2.5 mol m^?3 K, this was the major cation in both the cytoplasm and vacuole of mesophyll cells. However, in plants grown with 0.02 mol m^?3 K it declined to undetectable levels in the vacuole, although it was still detectable in the cytoplasm. In all plants, Ca was mainly located in epidermal cells. The implication of the results for explaining responses to K. in terms of compartmentation of solutes is discussed.     

Ribonucleic acid as an inducer of germination inhibition in Aegilops Kotschyi

Application of RNase or GA to dormant caryopses of AegilopsKotschyi accelerates normal hydrolysis of RNA during the firsthours of germination and also improves germination percentages.Glume extract of this species, known to have an inhibitory effecton germination, retards hydrolysis of RNA to some extent. Furthermore,Rifamycin, an inhibitor of RNA-polymerase, did not effect germination,although it inhibited later stages of seedling growth. The possibilityis discussed that dormant caryopses of Aegilops Kotschyi containa specific RNA fraction which is responsible for dormancy andthat the triggering of germination is dependent upon its degradation. ¹ This research was financed in part by a grant from the ResearchCouncil of Bar Ilan University. (Received August 8, 1970; )     

THE EFFECT OF CERTAIN SOIL TREATMENTS ON DIDYMELLA STEM-ROT OF TOMATOES

About 93% of Didymella lycopersici spores were destroyed after 4 weeks incubation in unsterilized soil. A survey of the microflora of glasshouse soil receiving different treatments and inoculated with D. lycopersici showed no clear relation between numbers of any group of organisms and the incidence of stem rot. Sterilized soil was not made toxic to D. lycopersici by the growth of a number of soil microorganisms even after 9 months incubation, but addition of unsterilized soil or of a suspension of unsterilized soil quickly restored toxicity. Direct observations of spores in soil on slides showed that their fate varied with the treatment of the soil before inoculation. With fresh soil or air-dry soil moistened 2 or more days before inoculation, lysis of spores occurred. With air-dry soil moistened and inoculated simultaneously, some spores germinated but growth of germ tubes soon ceased. No direct connexion could be seen between the fate of the spores and soil microorganisms. Addition of glucose to unsterilized soil reduced its toxicity to D. lycopersici. Soils steamed for 1 min. or longer were not toxic to D. lycopersici , but soils steamed for very short periods were as toxic as unsterilized soils although the soil microflora was much reduced.     

Radio-Tracking Timber Wolves in Ontario

Miniature collar-type transmitters originally designed by W.W. Cochran, Illinois, were adapted for use on timber wolves(Canis lupus sp.) in east-central Ontario. Wild timber wolveswere captured in steel traps, restrained with a forked stick,fitted with radio-collars and released at point of capture.Receivers were adapted for use in trucks, airplanes, and forwalking in rough bush country. Maximum ranges were 3.2 km withground and 9.6 km with aircraft receivers. A preadult femaletagged in July, 1964, and a lactating adult female tagged inJune, 1965, were tracked intermittently for 5.5 and 2.5 months,respectively. Tracking periods for six other animals of bothsexes, ranging in age from pups to adults, varied from 2 daysto 4 months. The lactating female and her associated pack regularlyreturned to three preferred "resting sites" for various periodsduring July and August. Preferred areas were well drained, semi-open,mixed conifer-hardwood stands in close proximity to swamps orbeaver ponds. The preadult female ranged in an area frequentedby a pack, but frequently remained independent of it. A preadultmale, tagged in the same region, wandered over a slightly largerarea than the female. Tagged animals were active throughoutall periods of the day or night. Activity increased slightlyduring the early evening hours. There was a slight correlationbetween weather conditions and patterns of behavior and activity.Apparently, tagged individuals were quickly accepted by othermembers of the pack.     

Biochemical and bioassay analysis of resistance of potato (Solanum tuberosum L.) cultivars to attack by the slug Deroceras reticulatum (Muller)

A method is described for using young field slugs Deroceras reticulatum (Muller) in a bioassay study of biochemical resistance of potato (Solanum tuberosum L.) cultivars to slugs. Tuber parts or an artificial diet were provided as food sources. Comparisons were made of feeding, survival and weight gain between the susceptible cultivar Maris Piper and the resistant cultivar Pentland Dell. Biochemical analyses were made of these two cultivars and the resistant cultivars Stormont Enterprise and Majestic. Comparisons of tuber sections and peelings as food sources indicated factors affecting growth were located in the surface layers of the tubers. Phenolics and glycoalkaloids were concentrated in the surface layers but the amounts were similar in the susceptible and resistant cultivars and the bioassays indicated that neither acting alone could explain resistance. The amounts and distribution of free amino acids also did not correlate with resistance although when supplied in the artificial diet they partly inhibited feeding. Proteinaceous inhibitors of slug gut proteolytic enzymes were present throughout the tubers but were not concentrated in the surface layers and the amounts were similar in the different cultivars thus they too did not explain the difference in susceptibility between the cultivars. Bioassays using acetone extracts (low molecular weight substances) and acetone powders (high molecular weight substances) either alone or in combination indicated that the resistant cultivar Pentland Dell contained a high molecular weight substance which together with a low molecular weight substance from either the same cultivar or the susceptible Maris Piper could confer resistance. Bioassays using protein extracts supplied in the presence or absence of chlorogenic acid indicated that this mechanism could comprise enzymic oxidation of phenolics. Assays of phenolase confirmed this since activity was highest in the outer layers of the tubers and was highest in the three resistant cultivars. Thus the chief resistance factor identified was high phenolase activity acting rapidly on phenolics when the slug first bites the tuber surface. The quantity of phenolics per se did not control the resistance. Thus while phenolics must be available, resistance is compatible with low blackening on cutting the tuber.     

The effect of direct supplementary feeding of nestlings on weight loss in female Great Tits Parus major

Experimentally hand-feeding nestlings of enlarged (+3 nestlings) broods reduced female weight loss during the nestling period in a single-brooded Great Tit Parus major population in Scotland but did not affect nestling size. The result is consistent with the existence of a trade-off in parental care between reproductive costs and benefits.