XVI International Botanical Congess

In live growing hyphal tips, microscopic Aoptical tweezers@ (?=820 nm laser, 1?m diam.) Are powerful, nondestructive experimental probes for altering patterns of hyphal morphogenesis. They can be manipulated to influence migration and position of the Spitzenkörper (Spk.) Or small organelles (esp. Secretory vesicles). If migrating vesicles are trapped and moved to a different site, localized wall bulges develop where the vesicles are newly concentrated. Shifts in transport or position of free vesicles or the Spk. Alter the direction of hyphal tip elongation, influence hyphal diameter, and modify apical or subapical cell profiles. Near-apical adventitious hyphal branches are included by manipulating vesicle transport or position of the Spk. The findings support the concept of an internal Amemory system@ for influencing direction of hyphal growth, and emphasize the role of vesicle transport, Spk. Position, and sites of vesicle concentration as major determinants of hyphal morphogenesis.