Studies on lignification in wheat (Triticum aestivum var. Thatcher) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Botany at Massey University

PART I Transections of the stem of Triticum were examined after staining with dyes specific for functional groups within the lignin polymer. Anatomical observations suggest that the basis for the rapid increase in the lignin content of this plant 35 to 40 days after germination, is the differentiation of subepidermal sclerenchyma fibres in the stem at this time. The lignin formed in the fibre walls appears to have a higher methoxyl content than the lignin of the xylem vessels. A comparison of the development of lignification with stem elongation and flowering was made and the interrelationship of these processes discussed. PART II The role of p-hydroxyphenyllactic acid in lignification in wheat was investigated. ¹⁴C-labelled tyrosine, p-hydroxyphenyllactic acid (HPLA), and ³H-labelled HPLA were administered separately to the cut ends of shoots of Triticum and the incorporation of label into ethanol-soluble and ethanol-insoluble ferulic (and in some cases only, p-hydroxycinnamic) acid was measured. On the basis of the pattern of incorporation of label from the ¹⁴C-tyrosine, experiments were carried out to determine the route by which HPLA is converted to lignin precursors. A failure to detect label from ³H-HPLA in the cinnamic acids suggests that HPLA is not dehydrated directly to p-hydroxycinnamic acid and is not of regulatory significance in lignification in either 10 or 40 day-old wheat plants. PART III Information from several levels of organization within the plant is drawn together and discussed. Suggestions for further work investigating the controlling factors in lignification are included

Cognitive aspects of emotional expression processing

This thesis investigates the hypothesis that emotions play an influential role in cognition. Interference between facial emotional expression processing and selected tasks is measured using a variety of experimental methods. Prior to the main experimental chapters, the collection and assessment (Chapter 2, Exp. 1) of stimulus materials is described. Experiments 2-11 then concentrate on the likelihood of interference with other types of information from the face. Findings using a Garner design suggest that, although identity processing may be independent of expression variation, expression processing may be influenced by variation in identity (Exps. 2-4). Continued use of this design with sex (Exps. 6-7) and gaze direction (Exps. 9-10) information appears to support the (mutual) independence of these facial dimensions from expression. This is, however, in contrast to studies that indicate the modification of masculinity judgements by expression (Exp. 5), and the interaction of gaze direction and expression when participants rate how interesting they find a face (Exp. 8). Further to this, a search task (Exp. 11) shows that slower responses to an angry (cf. happy) face looking at us, may be due to the presence of an aversive mouth. Experiments 12-15 test for interference in the field of time perception: complex interactions between expression and encoder and decoder sex are indicated. Finally, Experiments 16-17 find that exposure to a sequence in which the majority of faces are angry depresses probability learning, and that prior exposure to varying quantities of angry and happy faces affects our later memory for them. Overall, there is evidence that exposure to emotional expressions may affect other (selected)c ognitive processesd ependingu pon which expressionsa re used and which experimental methods are chosen. It is suggested that future investigations would benefit from techniques that describe the temporal profile of an emotional response