Anatomy of the garlic bulb and factors affecting bulb development

Abstract

THIS INVESTIGATION on the structure of garlic (Allium sativum L.) was undertaken to establish a background for cultural studies on garlic as a crop plant. While garlic is one of the oldest crops under cultivation, there have been few studies on either its structure or its development under field condi- tions. The data presented here are essentially descriptive; in only one or two in- stances were developmental studies made. All vegetative parts of the plant are described but not the seedstalks or flowers. Since any structural study should be closely related to the gross development of the plant in the field, data obtained on factors affecting plant development, especially bulbing and seedstalk formation, are included. As indicated above, the literature on garlic is limited. Several recent works have dealt with onion anatomy, and most of the references on this subject may be found in Hoffman (1933),8 Hector (1938), and Hayward (1938). Other references dealing with the anatomy of the various species of Allium- in some cases specifically with garlic-which should be added to the above list include the papers by Irmisch (1850), Falkenberg (1876), Tavel (1887), Baldrati (1897), Menz (1910, 1922), and Braecke (1921). General information on varieties of garlic and cultural problems is to be found in Beattie (1937), McCallum and Knott (1942), Comin (1942), Altstatt and Smith (1942), and Smith et al. (1944). About 80 per cent of the commercial garlic grown in the United States is produced in California (Rock, 1950). Here the crop is usually planted in fall or winter and begins growth with the fall rains. The plants grow slowly during the winter, more rapidly in the spring, and mature in June or July. All observations reported here were made on either the Early or Late varieties of garlic as described by McCallum and Knott (1942). There are few qualitative anatomical differences between the two varieties, so that, except in special cases, no varietal designations will be given. It should be noted that varietal names in garlic have mostly only local application, and it is difficult to determine from the literature any varietal synonymy for the different garlic-growing areas in the United States. The plant material from which slides, fresh sections, or cleared slices were prepared was almost entirely field-grown, using the common cultural pro- cedures. Craf fixatives, usually III or V, were used (Sass, 1940) and pre- pared slides, except as noted, were stained in aqueous safranin followed by progressive Heidenhain's hematoxylin. Cleared slices (plate 3) were pre- pared by treating fresh sections with one or more changes of lactic acid (sp. gr. 1.20, 25° C).