Department of Biology, Yale University, New Haven, Connecticut 06520.
Plant Physiol. 1968 Nov;43(11):1760-8. doi: 10.1104/pp.43.11.1760.
Explants of tobacco pith taken at various distances from the apex of a mature stem show a sharp gradient in growth potential in vitro; growth is highest in the extreme apical and basal explants, and is minimal in explants removed ca. 75 cm from the apex. Calluses produced by the vigorously growing basal explants are harder and more compact than those produced from more apical explants. The gradient in growth potential is directly correlated with gradients in RNA, protein of cell sap and soluble N per unit fresh weight, but is inversely correlated with peroxidase activity. Cell size increases from apex to base of plants.The peroxidase activity of pith explants is electrophoretically resolvable into 2 isoperoxidases, moving anodically at pH 9.0. During in vitro culture, this activity rises, due to the formation of several new isozymes moving toward the cathode. The appearance of these isozymes occurs most rapidly in apical and extreme basal explants.
取自成熟烟株不同部位的烟髓外植体在体外生长势表现出明显的梯度；最顶端和最基部的外植体生长势最强，距离顶端约 75 厘米处的外植体生长势最弱。强烈生长的基部外植体产生的愈伤组织比来自更顶端的外植体产生的愈伤组织更硬更紧实。生长势的梯度与 RNA、细胞溶质蛋白和单位鲜重可溶性氮的梯度直接相关，但与过氧化物酶活性呈负相关。细胞大小从植株的顶端到基部逐渐增大。髓外植体的过氧化物酶活性可电泳分离为 2 种同工酶，在 pH9.0 时向阳极移动。在体外培养过程中，由于形成了几种向阴极移动的新同工酶，该活性增加。这些同工酶的出现速度最快的是顶端和最基部的外植体。
