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Reproductive shoot (flower) Terminal bud Node Internode Terminal bud Vegetable shoot Leaf Shoot system Blade Petiole Axillary bud Stem Taproot Lateral roots Root system Roots Functions of roots: Anchoring the plant Absorbing minerals and water Often storing organic nutrients Root Hairs Prop roots. Storage roots. “Strangling” aerial roots. Buttress roots. Pneumatophores. Stems Stem Nodes points at which leaves are attached Internodes stem segments between nodes axillary bud has the potential to form a lateral shoot, or branch terminal bud located near the shoot tip causes elongation of a young shoot Stolons. Storage leaves Stem Roots Bulbs. Tubers. Rhizomes. Node Rhizome Root Leaves Leaf main photosynthetic organ consist of A flattened blade and a stalk petiole Monocots parallel veins Eudicots branching veins Simple leaf Petiole Axillary bud Leaflet Compound leaf Petiole Axillary bud Doubly compound leaf Leaflet Petiole Axillary bud Tendrils. Spines. Storage leaves. Bracts. Reproductive leaves. Plant Tissues Dermal Epidermis (nonwoody) Periderm (woody) Vascular Xylem Water & dissolved minerals Upward from roots to shoots Phloem organic nutrients Transports from location made to where they are needed Ground tissues Storage, photosynthesis, & support Dermal tissue Ground tissue Vascular tissue Some major types of plant cells: Parenchyma Collenchyma Sclerenchyma Water-conducting cells of the xylem Sugar-conducting cells of the phloem WATER-CONDUCTING CELLS OF THE XYLEM PARENCHYMA CELLS Vessel Parenchyma cells in Elodea leaf, with chloroplasts (LM) Tracheids 100 µm 60 µm Pits COLLENCHYMA CELLS 80 µm Cortical parenchyma cells Tracheids and vessels (colorized SEM) Vessel element Vessel elements with perforated end walls Tracheids SUGAR-CONDUCTING CELLS OF THE PHLOEM Collenchyma cells (in cortex of Sambucus, elderberry; cell walls stained red) (LM) Sieve-tube members: longitudinal view (LM) SCLERENCHYMA CELLS 5 µm Companion cell Sclereid cells in pear (LM) Sieve-tube member Plasmodesma 25 µm Sieve plate Cell wall Nucleus Cytoplasm Companion cell 30 µm 15 µm Fiber cells (transverse section from ash tree) (LM) Sieve-tube members: longitudinal view Sieve plate with pores (LM) Meristems Apical meristems located at the tips of roots and in the buds of shoots elongate shoots and roots primary growth Lateral meristems add thickness to woody plants secondary growth two types: vascular cambium adds layers of vascular tissue secondary xylem (wood) secondary phloem cork cambium replaces the epidermis with periderm thicker and tougher Primary growth in stems Shoot apical meristems (in buds) Epidermis Cortex Primary phloem Primary xylem Vascular cambium Lateral meristems Cork cambium Pith Secondary growth in stems Periderm Cork cambium Pith Cortex Primary phloem Primary xylem Root apical meristems Secondary xylem Secondary phloem Vascular cambium Terminal bud Bud scale Axillary buds Leaf scar This year’s growth (one year old) Node Stem Internode One-year-old side branch formed from axillary bud near shoot apex Leaf scar Last year’s growth (two years old) Scars left by terminal bud scales of previous winters Growth of two years ago (three years old) Leaf scar Primary Growth of Roots Zone of cell division Zone of elongation Zone of maturation Cortex Vascular cylinder Epidermis Key Root hair Dermal Zone of maturation Ground Vascular Zone of elongation Apical meristem Root cap 100 µm Zone of cell division Apical meristem Leaf primordia Developing vascular strand Axillary bud meristems 0.25 mm Phloem Xylem Sclerenchyma (fiber cells) Ground tissue Ground tissue connecting pith to cortex Pith Epidermis Key Cortex Epidermis Vascular bundles Dermal Vascular bundles Ground 1 mm A eudicot (sunflower) stem. Vascular bundles form a ring. Ground tissue toward the inside is called pith, and ground tissue toward the outside is called cortex. (LM of transverse section) Vascular 1 mm A monocot (maize) stem. Vascular bundles are scattered throughout the ground tissue. In such an arrangement, ground tissue is not partitioned into pith and cortex. (LM of transverse section) Key to labels Guard cells Dermal Stomatal pore Ground Vascular Cuticle Sclerenchyma fibers Epidermal cells 50 µm Surface view of a spiderwort (Tradescantia) leaf (LM) Stoma Upper epidermis Palisade mesophyll Bundlesheath cell Spongy mesophyll Lower epidermis Guard cells Cuticle Vein Xylem Phloem Cutaway drawing of leaf tissues Guard cells Vein Air spaces Guard cells 100 µm Transverse section of a lilac (Syringa) leaf (LM) Morphogenesis and Pattern Formation Pattern formation development of specific structures in specific locations determined by positional information signals indicating to each cell its location Ex. Polarity
