Mobility of boron in higher plants

硼是高等植物必需的营养元素之一。从培养基中撤出该元素后，立即会导致新叶和根尖的畸形。在开花和种子发育的生长阶段，对这种元素的需求是突出的。因此，与营养生长相比，缺硼对种子产量的影响更为严重。这在一定程度上是因为它在植物体内的流动性很差，即一旦元素被运送到目的地，它的再动员很少发生。因此，需要持续供应。作者利用稳定的B同位素来描述B的再动员作用。6周龄的向日葵植株有16~20片叶，在2.8 mmolm^~(-3)~(-3)的浓度下，用10B标记的硼酸饲喂3或6天，新施的B主要被输送到第2和第3叶，但对中年最大的叶片的转运较少。这表明S优先向发育较晚的叶片输送该元素。而B含量最高的部位是第一片叶。此外，在6-d^&lt；10&gt；B标记植株的第一片和第二片叶片中，有很大程度的检测到由^&lt；10.8&gt；B组成的老B。这些结果表明，一些B从植株的下部运输到最年轻的叶片。根B库参与了B从根到地的运输，并对其进行了表征。

Boron is one of the essential nutritional elements for higher plants. Malformation of new leaves and root tips are brought about immediately after withdrawal of this element from culture media. Requirement for this element is outstanding at growth stages of flower set and seed development. Therefore, B deficiency has a serious effect on seed yield compared with the effect on vegetative growth. This is partly due to its poor mobility in a plant body, that is, once the element is delivered to its destination, remobilization of it seldom occurrs. Therefore, continuous supply is needed. The author would like to depict the remobilization of B employing a stable isotope of B,^<10>B. Six-week old sunflower plants having 16 to 20 leaves were fed with 10B labeled boric acid at 2.8 mmol m^<-3> for 3 or 6 d. The newly-applied B was mainly transported to the 2nd and 3rd leaves, but not so much to the middle-aged largest leaves. This indicate s preferential delivery of the element to younger developing leaves. However, the highest B concentration was always detected in the first leaves. Furthermore, in the first and second leaves of the 6-d ^<10>B-labelled plants, old B which is composed of ^<10.8>B was detected to a significant extent. These results suggest that to the youngest leaf some of the B is transported from the lower parts of the plants. The root B pool which is involved in B transport from roots to shoots was also characterized.