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Plant tissues Made by: Kotánné Baló Krisztina Plant tissues Tissues are groups of cells of » similar shape, » similar structure, » and similar origin - specialized for a particular function » In plants tissues are grouped into two major categories: » meristematic and » permanent (consolidated) tissues Meristems • Where? -at the tip of the stem RESULT: GROWTH IN LENGTH -at the tip of the root RESULT : GROWTH IN THICKNESS -BETWEEN VASCULAR BUNDLES MERISTEMS Small cells with large nucleus and What are the characteristics of meristems? thin cell walls. The cells are tightly packed Because of their proliferative capacity parenchyma cells also serve as stem cells for wound healing and regeneration! Permanent tissues • Dermal tissues • Ground tissues • Vascular tissues Dermal tissue • Covers the outer surface of herbaceous plants • Features: -Its cells are closely packed -Its cells are transparent because they don’t contain chloroplasts (With one exception: guard cells) Epidermis -Covered by waxy cuticle layer against water loss, infections or damages ‘waxy bloom’ Cotton Dandelion Easter flower Epidermis Silver Lime/Linden for dispersion by wind Edelweiss - can have hairs for protecion against cold glandular hairs secrete perfume for protection against being eaten Pelargonium Stinging nettle for reducing water loss for protection against intense sunlight Mulleins Saintpaulia Rhizodermis No stomata Hairs for absorption Characteristics: No cuticle, no wax Functions of the dermal tissues • Protection • Evaporation • Gas exchange • Absorption Ground tissues • 1.Chlorenchyma: with many chloroplasts Ground tissues • 2. Storage parenchyma: with starch grains „Hot potato” Ground tissues • 3.Aerenchyma: air filled cavities and channels Ground tissues • 4.Water-storage parenchyma: mucilage bearing cells Ground tissues • 5.Storing and secreting parenchyma: latex, inclusions, anthocyanin, Tomato volatile oils Onion scale (skin) Red cabbage Colours scale (depending on the pH) Ground tissues • 6.Collenchyma (alive) • and sclerenchyma(dead): for supporting Fibers Stone cells ‘Gritty texture’ Vascular tissues • Complex, because contain a lot of cell types • are arranged in long, discrete strands called vascular bundles. -A bundle can be simple if it contains only xylem or only phloem. (Usually in roots) -A bundle can be complex if it contains both xylem and phloem with cambium between them Vascular tissues Two parts: • 1.Xylem: dead cells and vessels conducts water from the root upward to the leaves Its fibers are used in paper and furniture industry Vascular tissues • 2.Phloem: -living tissue, -carries organic nutrients(known as photosynthate), in particular, sucrose, -to all parts of the plant where needed Its fibers are used in textile industry Vascular tissues • Mixed vascular bundles in a dicot stem form a ring Mixed vascular bundles in a monocot stem have a typically scattered arrengement Summary Plant tissues meristematic Apical meristems cambium permanent Dermal tissues rhizodermis epidermis ground vascular chlorenchyma Parenchyma For starch storage Parenchyma For water storage aerenchyma Storing and secreting parenchyma Collenchyma and sclerenchyma xylem phloem