Growth! The plant cell tissue systems, tissues, and cells

Transcription

1 Growth! The plant cell tissue systems, tissues, and cells 1. Review of the plant body 2. The three tissue systems 3. Tissues that make up the tissue systems 4. Cell types that make up the tissues 5. Components of a cell The plant body has a hierarchy of organs, tissues, and cells, like multicellular animals Have organs composed of different tissues, which are in turn composed of cells The basic morphology of vascular plants Reflects their evolutionary history as terrestrial organisms that draw nutrients from two very different environments: below-ground and above-ground Figure 35.2 Morphology of a flowering plant: an overview Three basic organs evolved: roots, stems, and leaves They are organized into a root system and a shoot system The plant body has a hierarchy of organs, tissues, and cells, like multicellular animals Have organs composed of different tissues, which are in turn composed of cells The basic morphology of vascular plants Reflects their evolutionary history as terrestrial organisms that draw nutrients from two very different environments: belowground and above-ground Figure 35.2 Morphology of a flowering plant: an overview Three basic organs evolved: roots, stems, and leaves They are organized into a root system and a shoot system 1

2 Roots A root Is an organ that anchors the vascular plant Absorbs minerals and water Often stores organic nutrients In most plants The absorption of water and minerals occurs near the root tips, where vast numbers of tiny root hairs increase the surface area of the root Roots cont. Gymnosperms and eudicots: taproots with lateral roots Seedless vascular and monocots: fibrous root system: spread out Many plants have modified roots: adventitious roots arise above ground from stems and even leaves Many plants have modified roots Stems (shoot system) (a) Prop roots (b) Storage roots (c) Strangling aerial roots Nodes: point of leaf attachment Internodes: segments between nodes Axillary buds can form new shoots or branches Terminal buds can lead to apical dominance (grow up!) (d) Buttress roots (e) Pneumatophores Figure 35.4 Modified shoots: Stolons, strawberry (top left); rhizomes, iris (top right); tubers, potato (bottom left); bulb, onion (bottom right) 2

3 Leaves Figure 35.5 Simple versus compound leaves Main photosynthetic organ - but in many, the stems can dominate too. Blade and petiole (monocots don t have petioles - base of the leaf forms a sheath around leaf. Leaf types: Figure 35.6 Modified leaves: Tendrils, pea plant (top left); spines, cacti (top right); succulent (bottom left); brightly-colored leaves, poinsettia (bottom right) Figure Leaf anatomy Note: Cuticle = waxy or fatty layer on outer wall of epidermal cells 3

4 Leaf types The plant cell tissue systems, tissues, and cells 1. Review of the plant body 2. The three tissue systems 3. Tissues that make up the tissue systems 4. Cell types that make up the tissues 5. Components of a cell Figure 35.7 The three tissue systems The plant cell tissue systems, tissues, and cells 1. Review of the plant body 2. The three tissue systems 3. Tissues that make up the tissue systems 4. Cell types that make up the tissues 5. Components of a cell Figure 35.7 The three tissue systems Tissue Systems Ground Tissues Parenchyma Collenchyma Sclerenchyma Figure Primary tissues, and their functions, in young stems Sclerenchyma tissue: support of mature plant parts Xylem tissue: water & mineral transport; Phloem tissue: food (sugar) transport (a.k.a. pith ray ) Collenchyma tissue: support of young, growing parts Vascular Xylem Phloem Parenchyma tissue: photosynthesis, storage, and/or secretion Dermal Epidermis Epidermal tissue: protection, control of water loss, and a variety of other functions The three tissue systems 4

5 Figure Organization of primary tissues in young stems. Note difference from root: vascular tissue is arranged in bundles, with ground tissue in center. Also note difference in arrangement of bundles between dicot and monocot. Figure Organization of tissue systems and tissues in young roots Epidermis: Dermal system, epidermal tissue Cortex: Ground system, parenchyma tissue Stele: Vascular system, xylem & phloem tissues Figure Organization of primary tissues in young roots. Note the difference between the monocot and the dicot in the arrangement of the xylem & phloem in the stele. The plant cell tissue systems, tissues, and cells 1. Review of the plant body 2. The three tissue systems 3. Tissues that make up the tissue systems 4. Cell types that make up the tissues 5. Components of a cell Tissue Systems Ground Vascular Dermal Tissues (& cell types) Parenchyma (parenchyma cells, transfer cells) Collenchyma (collenchyma cells) Sclerenchyma (fibers & sclereids) Xylem (tracheids or vessel members, also some parenchyma cells, fibers, & sclereids ) Phloem (sieve cells or sieve-tube members, also specialized parenchyma cells called companion or albuminous cells, some fibers & sclereids) Epidermis (ground cells, guard cells, trichomes, and others, also some fibers & sclereids) Three tissue systems of plants Dermal tissue - outer protective covering Epidermis/periderm analogous to skin Cuticle - waxy coating to preserve water Vascular tissue - transport system Xylem: carries water and nutrients from roots to leaves. Support and food storage too. Phloem: transport organic nutrients (sugar), amino acids, lipids, hormones etc. Ground tissue - everything else. Pith (internal to vascular), Cortex Function in storage, photosynthesis, & support 5

6 Figure 35.8 The three tissue systems of a plant Dermal Tissue Plant Cell Types Epidermis Guard Cells Trichomes (appendages). Can be on roots (facilitate absorption), or on hairy leaves - reduce solar radiation in xerophytes). Some secrete salts (in halophiles) These cells provide mechanical protection Many are covered with a cuticle (cutin and wax) to minimize water loss Figure 35.8 The three tissue systems of a plant Ground Tissue pith cortex Plant Cell Types Epidermis Guard Cells Ground tissue Parenchyma: photosynthesis and metabolism (storage and secretion ). Collenchyma: support (flexible) Sclerenchyma: storage, support (firm), protection Parenchyma cells Alive at maturity No secondary walls Site of most plant metabolism Play a role in wound healing and regeneration Collenchyma cells Living at maturity No secondary cell walls or lignin Provide flexible support to growing parts of plant 6

7 Figure 35.8 The three tissue systems of a plant Sclerenchyma cells Thick secondary walls, usually with lignin Usually dead at maturity Usually specialized for support and strengthening of parts that have ceased elongating. Sclereids impart hardness to seed coats, shells of nuts (give pears their grit) Fibers are usually long, slender, tapered (hemp and flax fibers) Vascular Tissue Plant Cell Types Epidermis Guard Cells Ground tissue Parenchyma: photosynthesis and metabolism Collenchyma: support Scelerenchyma: support, storage, protection Vascular tissues Xylem: water and nutrients from roots. Also support and food storage Tracheids, vessel elements Phloem: sugars from leaves Sieve-tube members, companion cells Xylem cells Dead at maturity Tracheids found in all vascular plants Long and thin with tapered ends Lignin for structural support Less specialized than vessel elements ( safer though) Vessel elements found mainly in angiosperms (flowering plants) Generally wider, shorter, and less tapered than tracheids Has perforations for more efficient water flow - but perforations are open systems and can be less safe. Figure 35.8 Water-conducting cells of xylem tissue Phloem Primary and secondary phloem. Primary phloem is often destroyed during elongation of the organ. Principal conducting cells are the sieve elements ( with pores ) 7

8 Figure 35.9 Food-conducting cells of the phloem tissue Sieve-tube members Alive at maturity, but Lack nucleus, ribosomes, organelles (highly specialized like human red blood cells!) Served by nucleus etc. of adjacent companion cells Connected via plasmodesmata Figure Leaf anatomy Note: Cuticle = waxy or fatty layer on outer wall of epidermal cells Plant Growth 1. Meristems and overview of plant growth 2. Apical meristems and primary growth 3. Lateral meristems and secondary growth Remember: A major adaptation of land plants is the meristem a region of perpetual cell division that allows the plant to grow rapidly There are two types of meristems: Apical and lateral. Apical meristems lengthen the plant ( primary growth ). Lateral meristems thicken the plant with bark and wood ( secondary growth ). Figure Locations of major meristems Figure Illustration of primary and secondary growth: Morphology of a winter twig 8

9 Plant Growth Figure Primary growth of a root. Notice that the apical meristem produces three primary meristems, which produce the three primary tissue systems (dermal, ground, and vascular). 1. Meristems and overview of plant growth 2. Apical meristems and primary growth 3. Lateral meristems and secondary growth Figure Organization of primary tissues in young roots. Note the difference between the monocot and the dicot in the arrangement of the xylem & phloem in the stele. Figure The formation of lateral roots. Lateral roots arise from the pericycle the outermost cell layer of the stele. Figure Primary growth of a root. Notice that the apical meristem produces three primary meristems, which produce the three primary tissue systems (dermal, ground, and vascular). Figure The terminal bud and primary growth of a shoot. Just like in the root, the apical meristem produces three primary meristems, which develop into the three tissue systems. 9

10 Figure Organization of primary tissues in young stems. Note difference from root: vascular tissue is arranged in bundles, with ground tissue in center. Also note difference in arrangement of bundles between dicot and monocot. Plant Growth 1. Meristems and overview of plant growth 2. Apical meristems and primary growth 3. Lateral meristems and secondary growth Remember: Secondary growth happens at the 2 lateral meristems The interior lateral meristem, called the vascular cambium, produces secondary xylem (to the interior) and phloem (to the exterior). Figure Locations of major meristems Vascular cambium: Figure Secondary growth of a stem (Layer 1) Fusiform initials make cells elongated vertically, form secondary xylem (to inside) and secondary phloem (to the outside) Ray initials make cells elongated horizontally-transfer water and nutrients, store starch The exterior lateral meristem, called the cork cambium, produces cork cells to the exterior. Figure Secondary growth of a stem (Layer 2) Figure Secondary growth of a stem (Layer 3) Cork cambium: meristem for tough thick covering - replaces epidermis. Forms from cortex to fill in gaps as epidermis is stretched and broken by lateral expansion of stem Rays maintain connectivity between secondary xylem and secondary phloem, allow exchange of nutrients and water, store starch and organic nutrients 10

11 Anatomy of a three-year-old stem. How can you tell the stem is 3 years old? Secondary growth of a stem. How many years old is it? Notes: Wood = secondary xylem, or everything on the interior side of the vascular cambium Bark = everything exterior of the vascular cambium, including the secondary phloem and the periderm (cork cambium + cork) Also remember: Secondary growth happens in roots too. Figure Anatomy of a tree trunk A summary of primary and secondary growth in a woody stem Oldest xyelm nonfuctional Oldest phloem sloughed off Oldest xyelm nonfuctional Oldest phloem sloughed off 11