The process of differentiation gestation fertilisation growth( differentiation, gestation, fertilisation, growth ) is said to occur in a cell when some genes organelles enzymes ATPases( genes, organelles, enzymes, ATPases ) become more expressed and other become less expressed. The overall structure of the cell may change degrade become cancerous( change, degrade, become cancerous ) and the cell becomes specialised a stem cell a zygote a neurone( specialised, a stem cell, a zygote, a neurone ) to fulfil a certain role more efficiently with more protein synthesis with less protein synthesis in insulation( more efficiently, with more protein synthesis, with less protein synthesis, in insulation ). A group of such cells is called a tissue an organ a species a collection( a tissue, an organ, a species, a collection ).

The xylem vessel constitutes part of the vascular bundle package tube vein( bundle, package, tube, vein ) and is formed of dead cell remnants living cells extracellular matrix collagen( dead cell remnants, living cells, extracellular matrix, collagen ) joined end-to-end. The cell walls cytoplasm surface membranes( walls, cytoplasm, surface membranes ) are fortified with lignin lining cholesterol starch( lignin, lining, cholesterol, starch ) to make the xylem waterproof water soluble semi-permeable an active transporter( waterproof, water soluble, semi-permeable, an active transporter ) and strong flexible bendy variable( strong, flexible, bendy, variable ). The cell walls at the ends of the cells break down fuse swell bud off( break down, fuse, swell, bud off ), giving rise to a long, hollow tube.