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Plant tissues & organs - Coggle Diagram
Plant tissues & organs
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Mesophyll tissue
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spongy mesophyll tissue function = gaseous exchange - CO2 for photosynthesis & release O2 from respiration
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Epidermal tissue
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consists of flattened cells that (apart from guard cells) lack chloroplasts & form protective covering over leaves, stems & roots
some epidermal cells have walls impregnated with a waxy substance - forms waxy cuticle - important to plants living in dry places as reduces water loss
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Xylem tissue
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lignin can be deposited in rings, coils or spirals
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Phloem tissue
phloem sieve tubes transfer products of photosynthesis (mainly sucrose sugar) & amino acids, in solution from leaves to parts of plant that don't photosynthesise
sieve tubes lose most their organelles & sieve plates develop between them - phloem sap flows through the pores in sieve plates
companion cells retain their organelles & continue to metabolic functions to provide ATP for active loading of sugars into the sieve tubes
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Meristematic tissue
as most plant cells mature they develop a large vacuole & rigid cellulose cell wall - prevents the dividing
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meristematic tissue contains stem cells - from this tissue all other plant tissue are derived by differentiation
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Parenchyma, Sclerenchyma & collenchyma
parenchyma
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in aquatic places, arenchyma tissue is parenchyma tissue with air spaces to keep plants buoyant
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collenchyma
have thick cell walls & they strengthen vascular bundles & outer parts of stems, whilst also allowing some flexibility in these regions
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