Auxins, cytokinins, cell behaviour and leaf development (Nicotiana tabacum, Phaseolus vulgaris, Withania frutescens, Camellia sinensis)

This work is a contribution to the research field of leaf development.; Cultured mesophyll protoplasts of Nicotiana tabacum L. can be hormonally induced into different developmental pathways. Knowing that each hormone signal regulates a specific cellular process in cell suspension cultures, we detected these different processes in intact leaves and tried to correlate them with internal hormone concentrations. In meristematic tissue at the apex of a plant a correlation between division activity and auxin and cytokinins concentrations was observed, but in the leaf these relations were not detected. If the hormone balances are disturbed on whole plant level, leaf size is reduced. When a single leaf was subjected to changes in its endogenous hormone balance this resulted in a (limited) stimulation of leaf growth. We also investigated the impact of phytohormones when the tissue organisation is kept intact but isolated from the leaf. The responses were similar to these in cell cultures, but they were less vigorous.; In addition to the leaf development of tobacco we also studied the light-induced expansion of the primary bean (Phaseolus vulgaris L. Limburgse vroege) leaf. Cytokinin and auxin concentrations are high during a period preceding or coinciding with the most active period of cell division. The cell expansion activity induced by light only correlates with a lower concentration in cytokinins.; An important factor controlling the shape of a leaf is the cellulose orientation. Between the veins of a leaf the overall cellulose orientation of the epidermis cells is random, while elongated epidermis cells located on the top of a vein have an orientation parallel with the longitudinal axis.; In a tea research project in South Africa we investigated two stress sensitive and two stress tolerant tea clones (Camellia sinensis L.). A physiological measure of stress, leaf water potential, gave an indication of the sensitivity of the clones, but only for plants grown in unfavourable locations with higher stress. Among the morphological stress indicators studied, cuticle thickness was not reliable but the calculated maximum stomatal conductance appeared to be a good indicator, but again only for plants growing in unfavourable conditions. (Abstract shortened by UMI.)...