Formation of exclusive pattern during accumulation of ligno-suberic material in cell wall of Myrtaceae root tissues including epidermis, exodermis, endodermis and polyderm

Abstract

Details on localized deposition of biopolymers in cell wall have rarely been studied. Anatomical observation is important to understand tissue-specific accumulation of biopolymers and such knowledge can further clarify tissue-function. Myrtaceae roots possess alternating suberized and non-suberized cell layers known as polyderm that exist beyond the endodermis. It is important to understand firstly, where biopolymers accumulate in this tissue and secondly what mechanisms control cell wall modification. This study aims to study areas of biopolymer deposition in Myrtaceae root tissues. Root specimens were sectioned freehand or with an ultramicrotome after embedding in Technovit 7100 resin. Root sections were stained with berberine hemisulfate-aniline blue-safranin O series or just phloroglucinol and observed under a fluorescent or optical microscope. Different biopolymers accumulated alternatively on opposite sides of the cell wall in polyderm. In non-suberized tissues, lignin accumulation was dominant and its accumulation appeared to be "closed" centripetally resembling the letter "w". In suberized tissues, it resembled the letter "m". This tissue-specific accumulation pattern was common in all five Myrtaceae species. What factors could control and regulate such patterned and tissue-specific accumulation of biopolymers? Could this accumulation pattern itself be a contributing factor to its protective role? Discovery of this pattern, specific to Myrtaceae root polyderm, triggers more investigations on the effect of biotic and abiotic stress on biopolymer accumulation in it.