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 Procambium PHLOEM primary xylem protoxylem metaxylem primary phloem protophloem metaphloem tracheids tracheas xylem parenchyma cells xylem fibers Cellular elements: sieve cells sieve tubes companion cells phloem parenchyma cells phloem fibers
Cellular elements of vascular tissues PHLOEM sieve tube element with companion cell XYLEM cambiform cell phloem parenchyma phloem fiber c a m b i u m tracheid xylem parenchyma trachea element 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
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
Pitted cell wall thickening
annular bordered pits spiral
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: fiber tracheids cambiform cells divided xylem fibers divided phloem fibers supplementary fibers supplementary fibers
Types of vascular tissue arrangement Procambium contiguous fascicular annular vascular tissue vascular bundles
VASCULAR BUNDLE TYPES Simple Radial Compound Collateral Concentric closed open bicollateral amphicribral amphivasal
dicot root monocot stem dicot stem simple vasc.bundles phloem xylem phloem monocot root 1 closed collateral 2 open collateral 3 bicollateral 4 amphivasal 5 amphicribral xylem phloem xylem compound bundles
Ranunculus root cross section xylem bundle phloem bundle tetrarch root
Triticum root cross section xylem bundle polyarch root
phloem vascular cambium xylem closed collateral bundle (Lilium) open collateral bundle (Aristolochia)
Structure of open collateral bundle xylem: tracheid trachea sieve tube phloem companion cell parenchyma
xylem phloem cambium phloem Cucumis: bicollateral vascular bundle
Polypodium rhizome cross section xylem phloem amphicribral vascular bundle
Acorus calamus rhizome cross section xylem amphivasal vascular bundle phloem