Plant Form and Function Structure, Growth, and Development

The plant body has a hierarchy of organs, tissues, and cells There are three basic plant organs: Roots Stems Leaves

Roots Multicellular organs with important functions Anchoring the plant Absorbing minerals and water Storing organic nutrients Type Fibrous Roots Tap Roots Mycorrhizae fungus that forms a symbiotic relationship with some plants

Shoot System: Stems and Leaves Reproductive shoot (flower) Shoot System: Stems and Leaves Apical bud Node Internode Apical bud Stems – function primarily to display the leaves. Terminal Bud – area of growth at the top end of stem Axillary Buds – area of growth located in the V area between the leaf and the stem (branches) Leaves – main photosynthetic organ in plants Shoot system Vegetative shoot Blade Leaf Petiole Axillary bud Stem Taproot Lateral branch roots Root system

There are three basic groups of plant tissues: Dermal Tissue Single layer of closely packed cells Protects plant against water loss and invasion by pathogens and viruses Cuticle – waxy layer in leaves Vascular Tissue Xylem and phloem Ground Tissue Any tissue that’s not Dermal or Vascular tissue Pith – ground tissue located inside vascular tissue Cortex – ground tissue located outside the vascular tissue

5 Major Cell Types Parenchyma Collenchyma Sclerenchyma Xylem Phloem Most abundant present throughout plant most metabolism (photosynthesis) Collenchyma Grouped in cylinders, supports growing parts of plant Strings of celery (vascular tissue) is supported by collenchyma cells Sclerenchyma Exists in parts of the plant that are no longer growing Tough cell walls utilized for support Xylem Phloem

Parenchyma cells in Elodea leaf, with chloroplasts (LM) 60 µm Fig. 35-10a Figure 35.10 Examples of differentiated plant cells Parenchyma cells in Elodea leaf, with chloroplasts (LM) 60 µm

Collenchyma cells (in Helianthus stem) (LM) Fig. 35-10b 5 µm Figure 35.10 Examples of differentiated plant cells Collenchyma cells (in Helianthus stem) (LM)

Sclereid cells in pear (LM) Fig. 35-10c 5 µm Sclereid cells in pear (LM) 25 µm Cell wall Figure 35.10 Examples of differentiated plant cells Fiber cells (cross section from ash tree) (LM)

Vessel Tracheids Pits Tracheids and vessels (colorized SEM) Fig. 35-10d Vessel Tracheids 100 µm Pits Tracheids and vessels (colorized SEM) Figure 35.10 Examples of differentiated plant cells Perforation plate Vessel element Vessel elements, with perforated end walls Tracheids

longitudinal view (LM) 3 µm Fig. 35-10e Sieve-tube elements: longitudinal view (LM) 3 µm Sieve plate Sieve-tube element (left) and companion cell: cross section (TEM) Companion cells Sieve-tube elements Plasmodesma Sieve plate Figure 35.10 Examples of differentiated plant cells 30 µm 10 µm Nucleus of companion cells Sieve-tube elements: longitudinal view Sieve plate with pores (SEM)

Meristems generate cells for new organs Apical meristems Are located at the tips of roots and in buds of shoots. Sites of cell division that allow plants to grow in length (primary growth) Lateral meristems results in growth which thickens the shoots and roots (secondary growth)

Primary Growth lengthens roots and shoots Cortex Vascular cylinder Epidermis Key to labels Zone of differentiation Zone of cell division Includes apical meristem New cells produces Root cap is located in root Zone of elongation Elongation of cells Zone of maturation Cell differentiation Cell become functionally mature Root hair Dermal Ground Vascular Zone of elongation Apical meristem Zone of cell division Root cap 100 µm

Secondary Growth add girth to stems and roots in woody plants Two lateral meristems Vascular cambrium Produces secondary xylem (wood) Secondary phloem Cork cambrium Produces tough covering that replaces epidermis early in secondary growth Bark includes all the tissues outside the vascular cambrium.

Growth, morphogenesis, and differentiation produce the plant body development of body form and organization. This is the process of cell specialization