Movement, persistence and performance of fungitoxicants applied as pruning wound treatments on apple trees

The systemic fungicides triadimenol, fenpropimorph, furmecyclox and carben-dazim, applied to pruning wounds as solutions in a non-aqueous solvent containing N-methyl–2-pyrrolidone moved predominantly towards the trunk. Coriolus versicolor, introduced deliberately, moved both proximally and distally irrespective of whether it was introduced in the dormant or growing season. Natural resistance to damage by chemical or C. versicolor appeared to be greater in the growing than in the dormant season and was inhibited when a cationic surfactant was used to aid penetration of fungitoxicant into the wood. Against C. versicolor the non-systemic fungicide captafol was ineffective, furmecyclox or fenpropimorph gave some protection and triadimenol was very effective. Carbendazim, although inactive against wood-rotting basidiomycetes, moved extensively within the wood and persisted well, and so could be an effective treatment for ascomycete pathogens. It also stimulated callus formation. The mercuric oxide preparation Santar was effective in these experiments and also stimulated callus formation.     

Difference in nitrate reduction in "light" and "dark" stages of synchronously grown Chlorella pyrenoidosa and resultant metabolic changes

Using synchronized cells of Chlorella pyrenoidosa, the incorporationpatterns of ¹⁴C into various metabolites with and without nitrogensources were studied under steady-state and non steady-stateconditions. From the patterns it was found that the smallestcells which are divided in the dark utilize nitrate and nitritevery little, if at all. The importance of ammonia for regulation of secondary flow forChlorella is discussed and the suggested regulatory points aredescribed. ¹This work was sponsored, in part, by the U.S. Atomic EnergyCommission (Received January 26, 1970; )     

The influence of temperature on leaf development and growth in potatoes in controlled environments

Three controlled environment experiments were conducted at different temperatures to determine the relation between temperature and leaf development and growth in the potato (cv. Maris Piper). Developmental stages are defined for the appearance and duration of leaf extension in the potato and comparisons made with other temperate zone crops. The rate of leaf appearance was linear over the temperature range (9–25°C) and above 25°C there was no further increase in the rate. The temperature coefficient for the rate of appearance of leaves was 0.032 leaves (degree days)^-1 using a base temperature of 0°C. The duration of extension of an individual leaf decreased with increase in temperature up to 25°C such that the thermal duration was constant at 170 degree days using a base temperature of 0°C for leaf positions 4–10 on the main stem. At higher leaf positions the thermal duration was similar or greater. The advantages and limitations of controlled environment work as a parallel to field experimentation are discussed.     

Comparison of quantitative and molecular genetic variation of native vs. invasive populations of purple loosestrife (Lythrum salicaria L., Lythraceae)

Study of adaptive evolutionary changes in populations of invasive species can be advanced through the joint application of quantitative and population genetic methods. Using purple loosestrife as a model system, we investigated the relative roles of natural selection, genetic drift and gene flow in the invasive process by contrasting phenotypical and neutral genetic differentiation among native European and invasive North American populations ( Q _ST −  F _ST analysis). Our results indicate that invasive and native populations harbour comparable levels of amplified fragment length polymorphism variation, a pattern consistent with multiple independent introductions from a diverse European gene pool. However, it was observed that the genetic variation reduced during subsequent invasion, perhaps by founder effects and genetic drift. Comparison of genetically based quantitative trait differentiation ( Q _ST) with its expectation under neutrality ( F _ST) revealed no evidence of disruptive selection ( Q _ST >  F _ST) or stabilizing selection ( Q _ST <  F _ST). One exception was found for only one trait (the number of stems) showing significant sign of stabilizing selection across all populations. This suggests that there are difficulties in distinguishing the effects of nonadaptive population processes and natural selection. Multiple introductions of purple loosestrife may have created a genetic mixture from diverse source populations and increased population genetic diversity, but its link to the adaptive differentiation of invasive North American populations needs further research.     

Egg size, offspring quality and food level in planktonic rotifers

1. For two species of planktonic rotifers, Brachionus calyciflorus and Synchaeta pectinata , neonates from larger eggs were more resistant to starvation than neonates from smaller eggs, so egg size was positively correlated with offspring quality.
2. Theories of optimal offspring size in zooplankton predict either a decrease in offspring size with increasing food level, or maximum offspring size at intermediate food levels. In experiments using acclimated, even-aged individuals, neither rotifer species changed its egg size as predicted by theory. B . calyciflorus egg size increased with increasing food concentration, while S . pectinata egg size did not change.
3. The lack of fit to theory may have occurred because of constraints on minimum or maximum egg size, constraints on total reproductive effort, or because offspring fitness is influenced by traits in addition to neonate starvation time.     

Interspecific size and number variation in pollen grains and seeds

An interspecific correlation between pollen grain size and seed size is demonstrated by means of the phylogenetic regression, which allows for phylogenetic bias. The correlation was not explained by plant size, mass of DNA per cell, style length or breeding system, although the first three of these factors all correlated with both pollen size and seed size. Two interpretations, involving pollen competition and flower size, are discussed. There is also an interspecific correlation between pollen grain number per flower and ovule number per flower. Some consequences of these correlations for the interpretation of pollen-ovule ratios and sex allocation strategies are considered.