LEUCOPLASTS (from Gk. Xenc6s, Icakos, white + tr).acrr6s, plastos, formed. from r Ndcra-Etv, plassein, to form). Minute colorless bodies (also called Amy/op/was), whose special function it is to accumulate starch and sometimes proteids into solid granular form. They are special or gans of the protoplasm in active plant-cells. Sim ilar to these are the plastids. including ehromo plasts and ehloroplasts (qq.v.). They may occur in any cell, but are mostly readily ob served, because most abundant, in cells devoted to storage of reserve food. The starch-forming leucoplasts absorb the dissolved material (sugar?), convert it into starch, and begin to deposit this starch in their interior (see figure). The mature starch-grain is usually oval or round ish, rarely irregular. Structurally it is a sphere crystal, being composed of minute hair-like crys tals (trichiles), which radiate from a centre. Additions to the starch-grain, as it is growing, are made exclusively upon its surface. As the stareh-grain increases in size in the interior of the leucoplast. the latter is stretched. If the grain originates in the centre of the leucoplast the stretching may be uniform, in which ease nearly equal layers may be added to all sides.
More often, however, it arises eccentrically, and then the main portion of the leucoplast lies at one side of the starch-grain, the smaller portion being stretched until it forms a very thin, almost invisible, membrane. In this case the additions to the starch-grain will be more rapid on the side where the larger mass of the leucoplast lies. If the leucoplast is ruptured, remaining in contact with only one side of the starch-grain, further additions will be confined to portions in contact with the leucoplast (see figure). If a starch-grain begins to develop at more than one point, two or more may arise within a single leucoplast. pro ducing the so-called 'compound' starch-grains. The leucoplast is visible on the larger grains only after special treatment. In some cases leuco plasts accumulate in their interior masses of solid proteids which may or may not take the crystalline form. Such leucoplasts have recently been distinguished by the name proteinoplasts.