THE MECHANICS OF ANCHORAGE IN WHEAT TRITICUM-AESTIVUM L .1. THE ANCHORAGE OF WHEAT SEEDLINGS

Models of the mechanics of uprooting lead to the identification of 'optimal' anchorage systems which can withstand a given upward force at a minimum construction cost. Such systems have many downward-pointing fibrous roots which are strengthened progressively towards the base. A study of the anchorage system of 7- and 21-d-old wheat (Triticum aestivum L.) plants showed that the plants possessed five seminal roots, of which only three pointed vertically. Each root was well suited for anchorage, being covered in root hairs and strengthened progressively towards the base by lignification of the stele. Strength and stiffness of roots but not their mass per unit length increased with age. There was little interaction between roots when plants were uprooted; the three vertical roots broke while the two horizontal ones pulled out, as occurred when roots were pulled out singly. Uprooting forces increased with age and the root system could withstand uprooting forces greater than those required to pull out upper leaves, so reducing the chances of the plant being uprooted by a herbivore. By 3 weeks a stiff adventitious root system, which would later help prevent the wheat lodging, was developing.