Cole crops are the plants related to the genus Brassica and more specifically with the mustard family. The prominent members of this group are cauliflower, mustard, kale, Brussels's sprouts, broccoli and Kohlrabi This family is also known as cruciferous vegetables.
Boron is a vital micronutrient for the growth phase of plants. Gardeners and farmers are often face challenges with the deficiency of this nutrient which results in the lower fertilization and eventually production of fruits. The quantity of boron in a normal soil is limited (approximately 2 lb per acre to 20 lb per acre)
Boron plays a complex role in the growth stage of the plants. Boron is responsible for the transportation of sugars and carbohydrates in the plant. It also manages the delicate balance of starch and sugar in plant. This micronutrient plays a pivotal role in cell division, protein formation and nitrogen metabolism of cell. And hence directly influence seed formation and pollination. Over all boron is responsible for the structural integrity of cell wall in plants.
Cole crops needed very high amounts of boron in order to produce a good harvest. In acidic soils (pH less than 7 is considered acidic), boron is usually scarce. So in such case cruciferous vegetables shows crack, corky stem, petioles and midribs. Other symptoms are brown. Other symptoms included death of growing tips which later spread into the and killed the tips of lateral shoots too.
The deficiency of can be controlled by application of borax or sodium tetra borate at 20 kg ha. In case of acute deficiency, foliar spray of 0.25 to 0.50 per cent solution of boric acid is advocated.
To understand more about boron deficiency check the link http://www.spectrumanalytic.com/support/library/ff/B_Basics.htm