Nishiwaki M, Fujino K, Koda Y, Masuda K, Kikuta Y
Crop Physiology Laboratory, Graduate School of Agriculture, Hokkaido University, Sapporo, Japan.
Planta. 2000 Oct;211(5):756-9. doi: 10.1007/s004250000387.
Seedlings of carrot (Daucus carota L. cv. Red Cored Chantenay) formed somatic embryos when cultured on medium containing abscisic acid (ABA) as the sole source of growth regulator. The number of embryos per number of seedlings changed depending on the concentration of ABA added to the medium, with a maximum embryo number at 1 x 10(-4) M ABA. Seedling age was critical for response to exogenous ABA; no seedling with a hypocotyl longer than 3.0 cm was able to form an embryo. Removal of shoot apices from seedlings completely inhibited the embryogenesis induced by application of exogenous ABA, suggesting that the action of ABA requires some substance(s) that is translocated basipetally from shoot apices through hypocotyls. Histologically, somatic embryos shared common epidermal cells and differentiated not through the formation of embryogenic cell clumps, but directly from epidermal cells. These morphological traits are distinct from those of embryogenesis via formation of embryogenic cell clumps, which has been found in embryogenic carrot cultures established using 2,4-dichlorophenoxyacetic acid or other auxins. These results suggest that ABA acts as a signal substance in stress-induced carrot seedling somatic embryogenesis.
将胡萝卜（Daucus carota L. cv. Red Cored Chantenay）幼苗培养在以脱落酸（ABA）作为唯一生长调节剂来源的培养基上时，会形成体细胞胚。每株幼苗的胚数会因添加到培养基中的ABA浓度而异，在1×10⁻⁴ M ABA时胚数最多。幼苗年龄对外源ABA的反应至关重要；下胚轴长于3.0 cm的幼苗无法形成胚。从幼苗上去除茎尖完全抑制了外源ABA诱导的胚胎发生，这表明ABA的作用需要一些从茎尖通过下胚轴向基部转运的物质。组织学上，体细胞胚共享共同的表皮细胞，且不是通过形成胚性细胞团分化，而是直接从表皮细胞分化而来。这些形态特征与通过形成胚性细胞团的胚胎发生不同，后者已在使用2,4 - 二氯苯氧乙酸或其他生长素建立的胚性胡萝卜培养物中发现。这些结果表明，ABA在胁迫诱导的胡萝卜幼苗体细胞胚胎发生中起信号物质的作用。
