Biochemical studies on blossom end rot of tomatoes

The causes of cell wall necrosis in Blossom End Rot (BER) of tomatoes have been investigated by comparing enzyme activities in healthy and affected tissues in the cultivars Grenadier and Moneymaker. Changes in the mineral contents of the tomatoes were in accordance with those of calcium deficient tissues. The phenolic contents of the affected tissues were increased as also were caffeic and chlorogenic acids. Phenolase and peroxidase activities were higher in affected fruits white catalase activities were higher in healthy fruits. ¹⁴C-labelled leucine was incorporated into the proteins of the healthy fruits to the greatest extent but cell wall proteinbound hydroxyproline was greatest in affected fruits.     

The influence of germinating seeds and developing roots on re-establishment of micro-organisms in fumigated soil

A laboratory study was made of re-invasion of soils fumigated in closed containers at rates of 3 ml./sq.ft. 10 in. deep with chloropicrin, methyl bromide and a 67:33 mixture of the two materials (MBC–33), using the dilution plate method of determination. Counts after aeration, 3 weeks later, showed that all three fumigants eliminated practically all fungi. Chloropicrin and MBC–33 also killed almost all bacteria and actinomycetes, whereas fumigation with methyl bromide markedly increased numbers of bacteria without materially altering numbers of actinomycetes. Subsequently, in soils fumigated with chloropicrin or MBC–33, fungi recolonized rapidly, but up to 93 % of the colonies isolated were Trichoderma viride. Increase of fungi in soils fumigated with methyl bromide was slower and Penicillium spp. predominated. Bacteria at first declined in numbers, then increased rapidly in soils fumigated with all three materials. In soils fumigated with methyl bromide, actinomycetes, usually considered to include good antagonists, increased but did not exploit their initial advantage over fungi. In soils fumigated with chloropicrin and MBC–33 actinomycetes did not recolonize in appreciable numbers. The greatest variety of fungous genera occurred in isolates from rhizo-spheres of red beet, but the greatest numbers of colonies of both fungi and bacteria were isolated from rhizospheres of pea and pumpkin. None of the crops tested greatly stimulated recolonization by actinomycetes. Compared with the drastic changes brought about by fumigants the influence of seed and root exudates on either the magnitude or the composition of re-invading micro-organisms was slight.     

Heterophylly in Ranunculus flabellaris: The Effect of Abscisic Acid on Leaf Anatomy

Ranunculus flabellaris Raf., the yellow water crowfoot, exhibitsstriking heterophylly between submerged and terrestrial leaves.Leaves produced under water are highly divided with numerousnarrow lobes and deep sinuses, whereas terrestrial leaves havefew broad lobes and shallow sinuses. When plants are submergedin a 25 µM solution of ABA, the typical transition fromterrestrial to submerged leaves is completely suppressed and,instead, terrestrial-like leaves are produced. Image analysistechniques show that, in addition to this modification of leafmorphology, leaves produced under ABA treatment possess surfaceand internal features characteristic of terrestrial leaf anatomy.This study provides evidence that the environmental factorsthat influence the morphological and anatomical expression ofheterophylly may act through endogenous ABA. Ranunculus flabellaris, yellow water crowfoot, ABA, heterophylly, leaf anatomy     

Whole-body mechanics and kinematics of terrestrial locomotion in the Elegant-crested Tinamou Eudromia elegans

Whereas humans and certain birds experience an abrupt change in locomotor dynamics when shifting from walks to runs, a smooth walk–run transition characterizes many ground-dwelling birds. This study defines the biomechanical distinction between walks and runs in the Elegant-crested Tinamou Eudromia elegans using ground reaction forces. Three birds were filmed at 250 Hz from a lateral view as they moved over a force plate built into a trackway. Centre of mass mechanics and kinematic variables were analysed in 81 steady-speed trials that represented a speed range from 0.66 to 2.78 m/s. E. elegans undergoes two speed-related changes in locomotor mechanics. The first is a shift from walking strides that utilize vaulting mechanics to low-speed runs that exhibit bouncing mechanics; this transition occurs at Froude numbers between 0.4 and 0.6. Such low-speed runs exhibit duty factors exceeding 0.5 and, hence, lack an aerial phase between steps. The second transition, from grounded running to aerial running, occurs when duty factors decrease below 0.5. Grounded running in birds may enhance vision by stabilizing visual stimuli over the retina. The eventual incorporation of an aerial phase during running enables increased locomotor speeds primarily through longer stride lengths.     

Life history plasticity of Nemoura trispinosa (Plecoptera: Nemouridae) along a permanent-temporary water habitat gradient

1. The life history of the small herbivorous stonefly Nemoura trispinosa Claassen was studied in a variety of small springs in southern Ontario, Canada. Nymphs generally were able to tolerate a wide range of environmental conditions and were found in 78% of habitats sampled, although population densities differed markedly. 2. Life-cycle patterns varied from a univoltine, slow seasonal type to a univoltine, fast seasonal type with extended egg development. In one, highly stable, spring the life cycle was semivoltine. Inter-year variation was studied for 5 years in one spring and was found to be low relative to among-spring variation. 3. Differences in the life history traits of N. trispinosa populations from our spring series were most probably an expression of phenotypic plasticity rather than of genetic differentiation. 4. Maximum annual water temperature was the factor most influential on nymphal growth rate (non-linear relationship), whereas range in generation time was related to the degree of habitat permanence.     

Mini-exon Gene Sequences Define Six Groups within the Genus Crithidia

ABSTRACT. To develop molecular markers for lower trypanosmatids, we have examined the mini-exon gene repeats of 17 isolates that were classified as Crithidia by traditional methods. Representative repeats were amplified by polymerase chain reaction and the amplification products were cloned and used as hybridization probes against genomic DNA. Six hybridization groups of Crithidia were defined on the basis of the DNA blotting experiments. The three endosymbiont-bearing species ( C. deanei, C. desouzai and C. oncopelti ) and C. acanthocephali each belonged to single-member hybridization groups, while the C. fasciculata group contained additional named and undesignated species. The Crithidia lucilae thermophila probe hybridized to multiple undesignated isolates. The DNA sequence of the cloned products revealed that the specificity of the hybridization probes was due to substantial differences in the intron and the non-transcribed spacer regions. These data indicate substantial heterogeneity within the mini-exon gene locus of the taxon Crithidia .     

Isolation of polymorphic microsatellite markers in the sub‐Saharan tree,Acacia (Senegalia) mellifera (Fabaceae: Mimosoideae)

We isolated 11 polymorphic microsatellite markers from Acacia mellifera, a savannah woodland tree in sub‐Saharan Africa and southern Arabia. The loci were screened for polymorphism using 48 Kenyan individuals. Allelic diversity ranged from three to 19 per locus and the polymorphic information content varied from 0.287 to 0.893. These loci will be useful in studies of genetic structure, gene flow and breeding systems.     

The origin and fate of morphological intermediates between wild and cultivated soybeans in their natural habitats in Japan

The spread of transgenes into the genome of wild soybean is a concern when transgenic and wild soybeans are planted sympatrically. The objectives of this study were to investigate the origin and fate of morphological intermediates between wild and cultivated soybeans in their natural habitats in Japan. Twenty nuclear microsatellite and two chloroplast dCAPS markers were used to evaluate genetic variation of 468 wild, 17 intermediate, and 12 cultivated soybean samples collected from six sites between 2003 and 2006. Allelic differentiation of microsatellite markers between wild and cultivated soybeans was sufficient to detect their hybrids. Based on levels of observed heterozygosity, intermediate soybean plants were from two generations: either F₁ or an early segregating generation. Genetic admixture analysis and parentage assignment analysis revealed that the parents of all intermediate soybean plants could be assigned to a particular wild soybean plant and late‐maturing cultivar. The chloroplast DNA haplotypes revealed that all intermediate soybean plants originated from gene flow from cultivated to wild soybeans at all sites. Based on monitoring at both the phenotypic and molecular levels, hybrids quickly disappeared from natural habitats, and secondary gene flow from these plants to wild soybean was not detected. Thus, while gene flow from transgenic soybean into wild soybean can occur, gene introgression appears to be rare in natural habitats in Japan. This is the first report on the detection of gene flow from cultivated to wild soybean at the molecular level.