Effects of the nematicide oxamyl on life cycle stages of Globodera rostochiensis

Hatched second stage juveniles of Globodera rostochiensis were found to be more sensitive than either unhatched juveniles or adult males to low concentrations of oxamyl (EC₅₀ value for activity 0.5 μg oxamyl ml^-1). Development of juveniles in roots was significantly inhibited by 2.0 μg oxamyl ml^-1 probably due to impairment of normal feeding activity. The behavioural events necessary for orientation of juveniles towards roots for invasion and orientation of males towards females for fertilisation were found to be impaired by 0.5 and 1.0 μg oxamyl ml^-1 respectively. A comparison with previous work on Meloidogyne incognita showed G. rostochiensis juveniles to be more sensitive to oxamyl.     

Correlative Inhibition of Lateral Bud Growth in Phaseolus vulgaris L. Isolation of Indoleacetic Acid from the Inhibitory Region

The young, growing leaves have been shown by excision treatmentsto be responsible for the correlative inhibition of lateralbud growth in Phaseolus vulgaris. The presence of indoleaceticacid in apical portions of the stem bearing young leaves hasbeen demonstrated by extraction and collection in agar (‘agardiffusion’) followed by purification and analysis by bioassay,chromogenic assay, and gas chromatography-mass spectrometry.The relevance of these results to the possible involvement ofindoleacetic acid in correlative phenomena is discussed     

Interactions Between Physical and Biological Constraints in the Structure of the Inflorescences of the Araceae

A study of the inflorescences ofMonsteraandAnthuriumwas usedto establish a relationship between biological and physicalconstraints for the structure of plant organs. The physicalconstraint between flowers in the compact inflorescences ofAnthuriumandMonsteraisexpressed by Aboav-Weaire's law. The application of this lawto inflorescences indicates a linear relationship between thenumber of sides of a flower and the number of sides of neighbouringflowers. However, the slope of this straight line is significantlyhigher forAnthuriumandMonsterathan that expected in theory.This deviation from the law is attributable to a biologicalcause that can be estimated using Aboav-Weaire's law. Actingalone, the biological constraint tends to produce four-sidedflowers. The equilibrium between biological and physical constraintsreduces the number of sides per flower from six (theoreticalvalue) to 5.9 (inAnthurium) or 5.8 (inMonstera) with a varianceof the measures less than that expected in theory. Furthermore,when flower density in an inflorescence increases (towards themiddle of the inflorescence inMonsteraand towards the lowersection forAnthurium) the number of sides approaches six (i.e.the physical constraint dominates). When flower density decreases(towards the top of the inflorescence) the number of sides approaches5.5 (i.e. the biological constraint dominates). The geometryof the inflorescences ofAnthuriumandMonsterais the result ofthe joint action of biological and physical constraints.Copyright1998 Annals of Botany Company Monstera,Anthurium, Araceae, Aboav-Weaire, inflorescence, constraint, flower.