Different types of cells and tissues are present because organisms perform many specialised functions. Cells become structurally modified for particular tasks like protection, transport, support, movement and coordination, improving efficiency through division of labour in multicellular organisms.
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Meristematic cells lack vacuoles because they divide continuously and need dense cytoplasm for active metabolism. Large vacuoles would occupy space and reduce the efficiency of rapid cell division required for plant growth and tissue formation.
Plants grow after being cut because intercalary meristematic tissues remain active at nodes and internodes. These cells divide rapidly and produce new branches or shoots, helping grasses, hedges and other plants regenerate after cutting or grazing.
The increase in girth is caused by continuous division of cells in the lateral meristem. These cells form new tissues concentrically inside and outside the stem, increasing diameter, producing annual rings and strengthening the plant body over time.
Plant and animal tissues differ because plants are fixed and require support, transport and growth tissues. Animals move actively and need flexible tissues for movement, coordination and sensing. Their tissues develop differently according to nutrition methods, body structure and lifestyle.