Lactuca sativa cv. Baijianye seedlings do not normally produce lateral roots, but removal of the root tip or application of auxin, especially indole‐butyric acid, triggered the formation of lateral roots. Primordia initiated within 9 h and were fully developed after 24 h by activating the pericycle cells opposite the xylem pole. The pericycle cells divided asymmetrically into short and long cells. The short cells divided further to form primordia. The effect of root tip removal and auxin application was reversed by 6‐benzylaminopurine at concentrations >10−8 M. The cytokinin oxidase inhibitor N1‐(2chloro4pyridyl)‐N2‐phenylurea also suppressed auxin‐induced lateral rooting. The elongation of primary roots was promoted by L‐&agr;‐(2‐aminoethoxyvinyl) glycine and silver ions, but only the latter enhanced elongation of lateral roots. The data indicate that the induction of lateral roots is controlled by basipetally moving cytokinin and acropetally moving auxin. Lateral roots appear to not produce ethylene.

中文翻译：

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莴苣侧根的萌生和伸长

莴苣 cv. 白尖叶幼苗通常不产生侧根，但去除根尖或施用生长素，尤其是吲哚-丁酸，引发了侧根的形成。原基在 9 小时内启动，并在 24 小时后通过激活木质部极对面的周轮细胞完全发育。周环细胞不对称地分为短细胞和长细胞。短细胞进一步分裂形成原基。去除根尖和施用生长素的效果被浓度 > 10-8 M 的 6-苄氨基嘌呤逆转。细胞分裂素氧化酶抑制剂 N1-(2chloro4pyridyl)-N2-phenylurea 也抑制了生长素诱导的侧生根。L-&agr;-(2-氨基乙氧基乙烯基)甘氨酸和银离子促进了初生根的伸长，但只有后者增强了侧根的伸长。数据表明侧根的诱导受基叶移动的细胞分裂素和顶叶移动的生长素控制。侧根似乎不产生乙烯。