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Plant Structure: Organs Organs composed of 1 or more tissues Plant organs 3 major types: roots stems leaves Flowers and fruits evolved from stems and leaves Plant Structure: Roots 4 zones of growing root Root cap : protect tip of root; secretes lubricant Root structure

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Plant Structure: Organs

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Plant structure organs l.jpg

Plant Structure: Organs

  • Organs composed of 1 or more tissues

  • Plant organs

  • 3 major types:

  • roots

  • stems

  • leaves

  • Flowers and fruits evolved from stems and leaves


Plant structure roots l.jpg

Plant Structure: Roots

  • 4 zones of growing root

  • Rootcap: protect tip of root; secretes lubricant

  • Root structure

  • Celldivision: apical meristem; production of new cells

  • Cellelongation: expansion of cells due to enlarging vacuole

  • Cellmaturation: specialization of cells

  • root hairs

  • storage

  • vascular tissue


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  • Most water absorbed by root hairs

Plant Structure: Roots

  • Uptake of water and nutrients

  • Main functions of roots

  • Anchor and support

  • Water and nutrient uptake

  • Root hairs are projections of epidermal cells

  • Substantially increase surface area of roots


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Plant Structure: Roots

  • Fibrous, multibranched roots (e.g. lettuce)

  • Dominant tap root

  • Root types

  • Tap roots used to absorb water deep in soil

  • Some tap roots used to store carbohydrates (e.g. carrots)

  • Adventitious roots

  • root-like structures arising from stems or leaves

  • e.g. prop roots (e.g. corn) and holdfasts (e.g. poison ivy)

  • Tuberous roots

  • Swollen structure on fibrous root used to store carbohydrates (e.g. sweet potato)


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  • Stem Structure

Plant Structure: Stems

  • Nodes: location of leaves on stem

  • Stems

  • Internodes: stem between leaves

  • Buds: undeveloped leaves or flowers

  • Terminal (apical)

  • axillary (lateral)

  • Apical dominance is growth inhibition caused by apical bud


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Plant Structure: Stems

  • Functions

  • Support leaves, flowers, fruits

  • Stems

  • Transport of water (xylem) and products of photosynthesis (phloem)

  • Storage of carbohydrates

  • Tubers = swollen underground stems that store carbohydrates (e.g. potato; eyes are axillary buds)

  • Corm = swollen base of stem covered in papery leaves ( e.g. crocus)

  • Bulb = cluster of fleshy leaves attached to short, thick stem with basal roots (e.g. onion)

  • Bulbils = tiny bulbs arising in leaf axils (e.g. lily)

  • Rhizome = horizontal stem below ground that produces roots and shoots at each node ( e.g. iris, ferns)


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Plant Structure: Stems

  • Examples of stems modified for storage

  • Stems


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Plant Structure: Stems

  • Stems used only for asexual reproduction

  • Stolon (or runner) = horizontal stem that arises from leaf axil and runs above ground (e.g. strawberry, spider plant)

  • Stems

  • When tip of stolon hits ground a new plant forms


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  • Sucker = stem arising from root tissue, often from cut woody plant

Plant Structure: Stems

  • Other types of modified stems

  • Spur = stem with short internodes growing from a larger branch of woody plant

  • Stems

  • Waterspout = stem that arises from latent buds in branches of woody plants


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Plant Structure: Stems

  • Other types of modified stems

  • tendrils = twining stems used to secure climbing plants to vertical surfaces (e.g. peas, grapes)

  • Stems

  • prickles = tiny, pointed projections of epidermis tissues of stems (e.g. blackberry)

  • thorns =long, pointed projections produced in leaf axils (e.g. Hawthorn)

  • cladophylls =stems modified for photosynthesis (e.g. cacti, asparagus)


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Plant Structure: Stems

  • Examples of other modified stems

  • Stems


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