Host-parasite relationships in mycoparasite /

A mycoparasite, Piptocephalis virginiana ^ shows a resemblance to fungal parasites of higher plants in the fine structure of hyphae and haustoria. The morphology and fine structure of host and parasitic fungi have been described. The mode of penetration of the host cell, Choanephora cucurbitarum , probably involves mechanical forces. Although the presence of cell wall degrading enzyme was not detected by conventional techniques, its role in penetration can't be ruled out. A collar around the haustorial neck is formed as an extension of the host cell wall. No papilla was detected although appressorixim was seen during penetration. The young haustorium is enclosed in highly invaginating plasmalemma of the host cell and n\imerous cisternae of endoplasmic reticulum. Appearance of an electron—dense sheath around the mature haustorium seems to coincide with the disappearance of cisternae of endoplasmic reticulum from the host cystoplasm in the vicinity of the haustorium. The role of host cytoplasm particularly of endoplasmic reticulum in the development of the sheath is discussed. Extensive accumulation of spherosomes-like bodies, containing lipids, is found in haustorium, parasite and host hypha. Electron microscope revealed the parasiticculture spore has more lipid content than the axenic culture spore of P. virginiana . The biochemical and cytochemical tests also support these results. The mature spore of C. cucurbitarum possesses a thick three-layered cell wall, different from the hyphal wall. Its germination is accompanied by the formation of an elastic thin inner layer which surrounds the emerging germ tube and the growing hypha. High resolution autoradiography showed that H N-acetyl-glucosamine , a precursor of chitin, was incorporated preferentially in the thin inner layer of the spore wall and also in the cell wall of the growing hypha. When the label was fed to the infected cells, at different intervals after inoculation, grains were observed on the sheath which developed around the haustorium of P. virginiana , 30 hours after inoculation. The significance of these results in relation to the origin and composition of the sheath is discussed.

A contingency model of job satisfaction

The present research study was designed to test a contingency model of job satisfaction based on participation in decision making as the antecedent variable and job involvement as the intervening variable. The instruments used to measure the variables were the participation in decision making scale developed by Siegel and Ruh (1973), the job involvement scale by Lodahl and Kejner (1965) and the job satisfaction construct derived from Hoppock (1935). The findings indicate that statistically significant correlations do exist for the 1995 educators surveyed in this study. Educators who reported high levels of participation in decision making consistently reported high levels of job involvement (p!: 0.001). Also, teachers reporting high levels of job involvement consistently scored high on their levels of job satis faction (p!: 0.001). All major hypotheses were sUPFOrted by the data. Through exploratory hypotheses, the study attempted to develop statements of relationships between criteria of job satisfaction and sex and marital status of employees in the system. The hypotheses received only minimal support, but the results did highlight the impracticability of attempting to develop any such relationships without using definite personality and situational variables as moderators. Differences between male and female socialization, sex discrimination and multiplicity of roles are briefly discussed as possible explanations for the reported findings.