United States Department of Agriculture, ARS, SWC, Mineral Nutrition Laboratory, Beltsville, Maryland 20705.
Plant Physiol. 1967 Oct;42(10):1427-32. doi: 10.1104/pp.42.10.1427.
Tomato plants in solution culture were treated with 0 to 50 mum Mn, Co, or Zn in the presence of 5 mum Fe. Stem exudates were analyzed to determine quantities and forms of the metals translocated.Mn had no effect on exudate volume. Co and Zn at 5 mum and above depressed exudate volumes. Nutrient Mn was concentrated 2 to 5 times in the exudates. Co and Zn concentrations were between 1 and 3.Tomato roots treated with 0 to 10 mum Mn released into the exudate an average of 29% of the Fe they absorbed. They released 21% of the absorbed Fe when treated with 50 mum Mn. On 50 mum Co or Zn, the roots released only about 1% of the absorbed Fe.The exudates contained 12 to 47 mum citrate, which was usually considerably in excess of Fe. Electrophoresis of exudate revealed Fe as the only metal in anionic form. Mn, Co, and Zn migrated as cations.The concentration of Ca was >3 mm and Mg >1.5 mm in the exudates. Estimates based on metal-citrate equilibrium constants and constants of metal displacement caused by Ca and Mg confirmed that Mn, Co, and Zn were transported predominantly as inorganic cations in the stem exudates.
在含有 5 微米铁的情况下，将番茄植株置于溶液培养中，用 0 至 50 微米锰、钴或锌处理。分析茎分泌物以确定转运的金属的数量和形式。
锰对分泌物体积没有影响。5 微米及以上的钴和锌会抑制分泌物体积。营养锰在分泌物中浓缩 2 到 5 倍。钴和锌的浓度在 1 到 3 之间。
用 0 至 10 微米锰处理的番茄根平均将其吸收的铁的 29%释放到分泌物中。当用 50 微米锰处理时，它们释放了吸收的铁的 21%。在 50 微米的钴或锌上，根仅释放了吸收的铁的约 1%。
分泌物中含有 12 至 47 微米的柠檬酸，通常远远超过铁。分泌物的电泳显示铁为唯一的阴离子形式的金属。锰、钴和锌作为阳离子迁移。
分泌物中的钙浓度>3 毫米，镁>1.5 毫米。基于金属-柠檬酸平衡常数和钙和镁引起的金属置换常数的估计，证实锰、钴和锌在茎分泌物中主要作为无机阳离子运输。
