Due to the deficiency of Magnesium brown bast disease will appear on the bark as necrocis (dead tisue on bark). Magnesium is the carrier of phosphurous from the root to leaf through zylem which is a need for flowers. Magnesim is the metalic constitent of chlorophyll. For photosynthesis oxygen and hydrogen from soil and the carbon from carbon di oxide available in the air are required to prepare carbohydrates with the help of sunshine. This carbohydrates are flowing through phloem from leaf to root. Phospharous is the main item to grow roots. The cross section of tree is available in this page.
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My findings other than this will be published after November due to the International work shop on Brown bast/TPD with the participation of IRRDB, ANRPC and RRII.