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PHARMACOBOTANY LECTURE 5. PLANT TISSUES III. VASCULAR TISSUES VASCULAR TISSUES Xylem • transporting water and mineral substances • from the root upwards to other plant organs Phloem • carries photosynthetic assimilates • from the leaf (=place of photosynthesis) downwards to other plant organs Vascular tissues XYLEM PHLOEM Procambium primary xylem primary phloem protoxylem protophloem metaxylem metaphloem tracheids tracheas Cellular elements: sieve cells sieve tubes xylem parenchyma cells xylem fibers companion cells phloem parenchyma cells phloem fibers Cellular elements of vascular tissues sieve tube element with companion cell PHLOEM cambiform cell phloem parenchyma phloem fiber c xylem a parenm tracheid chyma b i u m trachea element XYLEM xylem fiber XYLEM – CELLULAR ELEMENTS Tracheids / Water-conducting cells: elongated cells, pointed end walls, lignified cell walls dead cells Tracheas / Vessels: trachea elements / vessel members dead cells, end walls are perforated or disappear Xylem parenchyma cells: living, cytoplasm-containing cells, storage (transport) Xylem fibers: elongated, lignified cell walls, dead cells supporting function XYLEM sclerenchyma fibers tracheids: primary cell wall with pores end wall primary cell wall with pores total perforation tracheids xylem elements Tracheas root of liquorice (Glycyrrhiza glabra) xylem fibers CELL WALL THICKENING I. CENTRIFUGAL - new cell wall material is deposited on outer surface of primary cell wall - cells not embedded in tissues (e.g. pollen, spores, trichomes) II. CENTRIPETAL - cell wall thickening inwards, towards cell lumen (1) Evenly • only certain walls (epidermis, endodermis) • each cell wall (sclereids, sclerenchyma fibers) (2) Unevenly • Affects smaller part of cell wall: annular, spiral, reticulate, scalariform • Affects larger part of cell wall: pits, bordered pits, channels in cell wall Centrifugal cell wall thickening pollen grains and spores Centripetal cell wall thickening b: annular c: spiral d: reticulate e: pitted f: channeled 1-3.: bordered pits spiral bordered pits annular pitted cell wall bordered pits PHLOEM – CELLULAR ELEMENTS Sieve cells: elongated, cylindrical, protoplasm containing living cells, with oblique, pitted or reticulate end walls • side walls: sieve areas with pores (cell-to-cell communication) - cytoplasm strands to adjacent cells Sieve tubes: sieve tube elements, end walls: perforated sieve plate Companion cells: accompany sieve tube elements in angiosperms; living cells containing cytoplasm and nucleus Phloem parenchyma cells: living, cytoplasm-containing, storing nutrients Phloem fibers: elongated, sharply tapering ends, cellulose walls, strengthen the vascular tissue sclerenchyma cells PHLOEM sieve plate sieve element companion cell e: epidermis ek: primary cortex hr: phloem fiber h: phloem k: cambium phloem fibers of hemp Vascular tissues Cambial ring / Vascular cambium secondary xylem secondary phloem a) cellular elements – like in primary xylem phloem b) transitory elements: cambiform cells fiber tracheids divided phloem fibers divided xylem fibers supplementary fibers supplementary fibers Types of vascular tissue arrangement Procambium contiguous annular vascular tissue fascicular vascular bundles VASCULAR BUNDLE TYPES Simple Radial Collateral closed open Compound Concentric bicollateral amphicribral amphivasal phloem xylem cambium monocot stem dicot root simple vasc.bundles dicot stem phloem xylem phloem monocot root xylem 1 closed collateral 2 open collateral 3 bicollateral 4 amphivasal 5 amphicribral phloem xylem compound bundles Vascular bundles in circle – dicot plants stem of Ambrosia artemisiifolia stem of Aquilegia sp. Scattered vascular bundles – monocot plants stem of maize (Zea mays) rhizome of Iris sp. phloem xylem closed collateral bundle (Lilium) open collateral bundle (Aristolochia) vascular cambium Structure of open collateral bundle xylem: tracheid trachea sieve tube phloem companion cell parenchyma Collateral open bundles petiole of Tussilago farfara stem of Aquilegia sp. Collateral closed bundles leaf of eucalyptus Collateral closed bundles stem of maize xylem phloem cambium phloem Cucumis: bicollateral vascular bundle Polypodium rhizome cross section xylem phloem amphicribral vascular bundle Acorus calamus rhizome cross section amphivasal vascular bundle xylem phloem Bundle sheats flower of Tilia sp. leaf of oleander Thickening types of the stem Helianthus type Aristolochia type Ricinus type Tilia type stem of St. John’s wort Structure of woody stems rhytidoma Pinus fiatal ág4x phloem xylem resin duct cambium epithel cells young stem of Pinus griffithii cells of ground tissue rhizome of Tussilago farfara Root Triticum root cross section xylem bundle polyarch root Ranunculus root cross section xylem bundle phloem bundle tetrarch root aerial root of philodendron (Monstera deliciosa) xylem phloem
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