ROOTS. Syllabus Theme A Plant Structure and Function. Root systems. Primary Growth of Roots. Taproot system. Fibrous root system.

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Syllabus Theme A lant Structure and Function A2: Structure and function of the basic plant organs ampbell & Reece hap.

minerals occurs near the root tips Vast numbers of tiny root hairs function?

extend from the main root Fibrous root system Multiple adventitious roots of the same size (developing from the end of the

1 Syllabus Theme A lant Structure and Function A2: Structure and function of the basic plant organs ampbell & Reece hap. 35 Selected page numbers ROOTS Functions Anchors the vascular plant Absorbs minerals and water The absorption of water and minerals occurs near the root tips Vast numbers of tiny root hairs function? Often stores organic nutrients Taproot system Root systems One main root formed from the radicle Multiple lateral roots extend from the main root Fibrous root system Multiple adventitious roots of the same size (developing from the end of the stem) Multiple lateral roots branching off from the adventitious roots Taproot system Fibrous root system Many plants have modified roots What is a modified root? rop roots Storage roots Strangling aerial roots rimary Growth of Roots The root tip is covered by a root cap Function? Dermal ortex cylinder Root hair Zone of maturation Zone of elongation Apical meristem Root cap Zone of cell division Buttress roots neumatophores 1

Tissue Organization of Roots The primary growth of roots roduces the epidermis, ground tissue, and vascular tissue EUDIOT ortex cylinder Endodermis ericycle ith ylem hloem MONOOT ylem hloem

lateral root Lateral root STEMS A stem is an organ consisting of An alternating system of nodes, the points at which leaves are attached Internodes, the stem segments between nodes An axillary

loosely-arranged cells allowing oxygen to diffuse into interior of woody stem A Bud scale Many plants have modified stems This year s growth (one year old) B Leaf scar Stem D Storage leaves

2 Tissue Organization of Roots The primary growth of roots roduces the epidermis, ground tissue, and vascular tissue EUDIOT ortex cylinder Endodermis ericycle ith ylem hloem MONOOT ylem hloem ortex ith (monocots) Endodermis ericycle ylem Dermal hloem 50 µm Lateral roots Arise from within the pericycle, the outermost cell layer in the vascular cylinder ortex 1 cylinder Emerging lateral root Lateral root STEMS A stem is an organ consisting of An alternating system of nodes, the points at which leaves are attached Internodes, the stem segments between nodes An axillary bud Is a structure that has the potential to form a lateral shoot, or branch A terminal bud Is located near the shoot tip and causes elongation of a young shoot Lenticels are sites of loosely-arranged cells allowing oxygen to diffuse into interior of woody stem A Bud scale Many plants have modified stems This year s growth (one year old) B Leaf scar Stem D Storage leaves STOLONS Last year s growth (two years old) Leaf scar Scars left by terminal bud scales of previous winters Stem RHIZOMES Growth of two years ago (three years old) Leaf scar Root BULBS TUBERS Rhizome Node Root 2

rimary Growth of Shoots A shoot apical meristem Is a dome-shaped mass of dividing

leafbearing nodes Apical meristem Leaf primordia Tissue Organization of Stems In

arranged in a ring and a distinct cortex and pith hloemylem Sclerenchyma (fiber

scattered throughout the ground tissue tissue bundles 1 mm Occurs in stems and

3 rimary Growth of Shoots A shoot apical meristem Is a dome-shaped mass of dividing cells at the tip of the terminal bud Gives rise to a repetition of internodes and leafbearing nodes Apical meristem Leaf primordia Tissue Organization of Stems In gymnosperms and most eudicots The vascular tissue consists of vascular bundles arranged in a ring and a distinct cortex and pith hloemylem Sclerenchyma (fiber cells) tissue connecting pith to cortex Developing vascular strand meristems bundle ith ortex Dermal 1 mm 0.25 mm Tissue Organization of Stems In most monocot stems The vascular bundles are scattered throughout the ground tissue tissue bundles 1 mm Occurs in stems and roots of woody plants but rarely in leaves onsists of the tissues produced by the vascular cambium and cork cambium Name them! Secondary Growth 3

ambium and Secondary Tissue cambium ylinder of meristematic cells one cell thick Develops from parenchyma cells roduces Secondary xylem (wood) to the inside (inner bark) to the

plus the layers of cork cells it produces Bark onsists of all the tissues external to the vascular cambium, including secondary phloem and periderm 1 cambium Secondary Late

5 mm Bark Secondary xylem cambium rimary phloem 4 First cork cambium Growth ork 6 Secondary xylem (two years of production) cambium 5 Most recent cork cambium 9 Bark 7 ork 8

water and nutrients laterally) Also store starch cambium As a tree or woody shrub ages The older layers of secondary xylem, the heartwood, no longer transport water and

4 ambium and Secondary Tissue cambium ylinder of meristematic cells one cell thick Develops from parenchyma cells roduces Secondary xylem (wood) to the inside (inner bark) to the outside ork ambium and the roduction of eriderm The cork cambium Gives rise to the secondary plant body s protective covering, the periderm eriderm onsists of the cork cambium plus the layers of cork cells it produces Bark onsists of all the tissues external to the vascular cambium, including secondary phloem and periderm 1 cambium Secondary Late wood xylem Early wood ork cambium ork eriderm ith rimary xylem cambium rimary phloem ortex 2 hloem ray 3 ylem ray Growth rimary xylem 0.5 mm ylem ray 0.5 mm Bark Secondary xylem cambium rimary phloem 4 First cork cambium Growth ork 6 Secondary xylem (two years of production) cambium 5 Most recent cork cambium 9 Bark 7 ork 8 Layers of periderm cambium appears as a ring, with regions of dividing cells fusiform initials produce xylem and phloem tissue cells ray initials produce vascular rays (move water and nutrients laterally) Also store starch cambium As a tree or woody shrub ages The older layers of secondary xylem, the heartwood, no longer transport water and minerals Is darker has resin that protects against fungi/insects loser to the centre of the stem The outer layers, known as sapwood Still transport materials through the xylem Is lighter loser to the vascular cambium 4

Growth ring LEAVES Secondary xylem ray Heartwood Sapwood cambium The main

Layers of periderm In classifying angiosperms Taxonomists may use leaf

leaf etiole Leaflet etiole Leaflet etiole Monocots and dicots Differ in the

veins Most dicots Have branching veins (net veined) innately palmately Leaf

stem may be Alternate (one leaf at each node) Opposite (two leaves at each node)

5 Growth ring LEAVES Secondary xylem ray Heartwood Sapwood cambium The main photosynthetic organ of most vascular plants Leaves generally consist of Bark Layers of periderm In classifying angiosperms Taxonomists may use leaf morphology as a criterion Simple leaf ompound leaf Double (bipinnately) compound leaf etiole Leaflet etiole Leaflet etiole Monocots and dicots Differ in the arrangement of veins, the vascular tissue of leaves Most monocots Have parallel veins Most dicots Have branching veins (net veined) innately palmately Leaf venation Leaf arrangement Many plants have modified leaves Leaf arrangement on a stem may be Alternate (one leaf at each node) Opposite (two leaves at each node) Whorled (three or more leaves at each node) Tendrils Spines Storage leaves Bracts Reproductive leaves 5

6 Tissue Organization of Leaves The epidermal barrier Has stomata gaseous exchange and transpiration oated by a waxy cuticle why? The ground tissue - mesophyll Is sandwiched between the adaxial and abaxial epidermis The vascular tissue Is continuous with the vascular tissue of the stem to labels Dermal Sclerenchyma uticle fibers Stoma Adaxial epidermis alisade mesophyll Bundlesheath cell Spongy mesophyll Abaxial epidermis Guard cells uticle ylem Vein hloem Guard cells (a) utaway drawing of leaf tissues MONOOTS annot distinguish between palisade parenchyma and spongy mesophyll resence of bulliform cells (mainly grasses) hotosynthesis and leaf structure Broad, flattened leaf blade Stomata Transparent epidermis Air spaces in mesophyll tissue 6

Plants. Tissues, Organs, and Systems

Plants. Tissues, Organs, and Systems Plants Tissues, Organs, and Systems Meristematic cells Specialized cells that are responsible for producing specialized cells, they produce three types of tissue in the body of a plant. Meristematic Cells