Orientation of wheat seedling organs in relation to gravity

Seedlings of wheat (Triticum aestivum L.) were grown in special holders that permitted the coleoptile and early roots to develop in moist air. The orientation of the organs of seedlings erect to gravity was compared with that of organs produced on a horizontal clinostat. Orientation was described by the angular position of each organ tip with reference to the axis of the embryo. Comparative tests were also made with barley, rye, and oat seedlings.The coleoptile of all species developed curvatures in 3 dimensions when geotropic responses were eliminated. The primary root was not precise in its positive geotropism. Seedlings grew on clinostats with much greater variations in the lateral orientation of the central root and with a tendency for it to curve away from the endosperm to a greater degree than in erect seedlings.The symmetry of root system in wheat was found to depend on a specific mechanism. Under the influence of gravity the earliest lateral roots were oriented in a plane at characteristic angles of about 57.5 degrees with the ideal primary root. The corresponding angles for lateral roots growing on clinostats were greater by about 47.5 degrees as a result of epinasty not previously reported in roots. This force also appeared to be active in the seminal roots of barley and rye but not of oats.The curvatures in coleoptiles grown without the directional effects of gravity correspond to the results of growth imbalance in Coleus stems in the absence of lateral transport of their auxin by gravity. Root epinasty appears to be based on auxin imbalance. Curvatures in the primary root are also interpreted as results of asymmetrical distribution of growth hormone.

Structural evidence that the small subunit found associated with the TL antigen is beta 2-microglobulin

Comparative tryptic peptide mapping and partial amino-terminal primary sequence analysis of the light chain component associated with the TL antigens showed that the small subunit of TL was identical to the beta 2m light chain associated with the H-2K or D product of the same strain. Peptide comparison of the beta 2m from the Tla products of an A strain X-ray induced leukemia RADA1 (Tlaa) and of a C57BL/6 strain X-ray induced leukemia ERLD (Tlab) showed differences to the extent of 25-35% in their peptides. This is consistent with previous results showing beta 2m allelic variations between these mouse strains. The data prove the structural identity of the beta 2m molecules from TL and H-2K, D antigens as well as reveal the strain specific polymorphism of the beta 2m associated with these products.