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Plant Tissues Chapter 28
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Monocots and Dicots 1 cotyledon 2 cotyledons 4 or 5 floral parts
Netlike veins Parallel veins 3 pores 1 pore Vascular bundles in ring Vascular bundles dispersed
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Meristems Apical responsible for primary growth stems, roots lengthen
Lateral responsible for secondary growth increases width
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Apical Meristems Apical meristems
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Apical Meristems Shoot apical meristem Root apical meristem
activity at meristems Apical Meristems new cells elongate and start to differentiate into primary tissues Shoot apical meristem new cells elongate and start to differentiate into primary tissues Root apical meristem activity at meristems
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Apical Meristem Produces 3 types of specialized tissue common to the stems, branches, leaves and roots Dermal tissue meristematic forms outer protective covering non-woody plants epidermis woody plants periderm root hairs
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trichomes found in stems, leaves and reproductive organs protect plants from too much sun conserve moisture leaves cuticle lower epidermis contains guard cells stomata
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photosynthetic cell leaf surface cuticle epidermal cell 8
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Apical Meristem Ground tissue ground meristem fill interior of plant
5 types Parenchyma pliable, alive most abundant rapidly goes through mitosis perform the most metabolic functions
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fibers of sclerenchyma
vessel of xylem parenchyma phloem simple and complex tissues inside the stem stem epidermis 10
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Apical Meristem Collenchyma cells elongate stretchable tissue
thicker walls contain pectin alive at maturity Schlerenchyma dead at functional maturity lined with lignin acts like cement used for support 2 types fibers sclereids
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lignified secondary wall
collenchyma parenchyma lignified secondary wall 12
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Water-conducting cells of the xylem are dead at functional maturity
There are two types of water-conducting cells Tracheids are long, thin cells with tapered ends that move water Vessel elements align end to end to form long micro-pipes 13
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100 m Vessel Tracheids Pits Tracheids and vessels (colorized SEM)
Figure 28.9d Exploring examples of differentiated plant cells (part 4: water-conducting cells of the xylem) Perforation plate Vessel element Vessel elements, with perforated end walls Tracheids 14
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Sugar-conducting cells of the phloem are alive at functional maturity
In angiosperms, sugars are transported in sieve tubes, chains of cells called sieve-tube elements Sieve plates are the porous end walls that allow fluid to flow between cells along the sieve tube Sieve-tube elements lack organelles, but each has a companion cell whose nucleus and ribosomes serve both cells 15
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longitudinal view (LM) 3 m
Sieve-tube elements: longitudinal view (LM) 3 m Sieve plate Sieve-tube element (left) and companion cell: cross section (TEM) Companion cells Sieve-tube elements Plasmodesma Sieve plate Figure 28.9e Exploring examples of differentiated plant cells (part 5: sugar-conducting cells of the phloem) 30 m Nucleus of companion cell 15 m Sieve-tube elements: longitudinal view Sieve plate with pores (LM) 16
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Plant Tissues Ground tissues 17
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Apical Meristem Vascular tissue procambium
gives rise to vascular tissue transports water and nutrients provides support 2 main types
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Xylem Conducts water and dissolved minerals
Conducting cells are dead and hollow at maturity vessel member tracheids 19
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Phloem Transports sugars Main conducting cells are sieve-tube members
Companion cells assist in the loading of sugars sieve plate sieve-tube member companion cell 20
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Vascular Tissues Vascular tissues 21
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Lateral Meristems Lateral meristems add thickness to woody plants, a process called secondary growth There are two lateral meristems vascular cambium adds layers of vascular tissue called secondary xylem (wood) and secondary phloem cork cambium replaces the epidermis with periderm, which is thicker and tougher 22
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3 Vegetative Organs (1) Root system anchor plants
absorbing minerals and water root hairs produce hormones store food (carbohydrates)
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Root Structure Root cap covers tip Apical meristem produces the cap
Cell divisions at the apical meristem cause the root to lengthen Farther up, cells differentiate and mature
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Root Structure 3 zones Cell division Provide cells for next zone
Elongation Cells lengthen as they specialize Maturation Fully differentiated cells Root hairs form
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Root: Internal Structure
Outermost layer is epidermis Root cortex is beneath the epidermis made of parenchyma cells contain starch granules function as food storage leucoplast air passes through
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Internal Structure of a Root
Endodermis boundary between cortex and vascular cylinder bordered with lignin and suberin called casparin strip controls the movement of water and dissolved substances into the vascular cylinder
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Internal Structure of a Root
Vascular cylinder pericycle 1st layer gives rise to lateral roots dicots - star shaped monocots - circle new lateral root
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A taproot, the main vertical root
Tall, erect plants with large shoot masses have a taproot system, which consists of A taproot, the main vertical root Lateral roots branching off the taproot Small or trailing plants have a fibrous root system, which consists of Adventitious roots that arise from stems Lateral roots that arise from the adventitious roots and form their own lateral roots 29
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Stems (2) Shoot system (stems)
Stems are covered in epidermis and contain vascular bundles that run the length of the stem Lateral shoots develop from axillary buds on the stem’s surface carry out reproductive functions
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Stems Vascular bundles Xylem faces outward Phloem faces inward
Meristem tissue between Herbaceous stems only have primary growth Woody stems have secondary growth bark thicker, tougher layers of vascular tissue wood secondary xylem accumulates over the years
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Secondary Growth Occurs in all gymnosperms, some monocots, and many dicots A ring of vascular cambium produces secondary xylem and phloem Wood is the accumulation of these secondary tissues, especially xylem
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Secondary Growth Secondary growth
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Annual Rings Annual rings
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Annual Rings Narrow annual rings mark severe drought years 1587–1589
1606–1612
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Stolon Rhizome Root Rhizomes Stolons Tubers
Figure 28.6 Evolutionary adaptations of stems Tubers 36
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Adapted for Photosynthesis
(3) Leaves main photosynthetic structure Leaves are usually thin high surface area-to-volume ratio promotes diffusion of carbon dioxide in, oxygen out Leaves are arranged to capture sunlight are held perpendicular to rays of sun arranged so they don’t shade one another
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Leaf Structure Leaf organization
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Leaf Structure UPPER EPIDERMIS cuticle PALISADE MESOPHYLL xylem SPONGY
phloem LOWER EPIDERMIS one stoma CO2 O2
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Tissue Organization of Leaves
The epidermis in leaves is interrupted by stomata allow CO2 and O2 exchange between the air and the photosynthetic cells in a leaf Each stomatal pore is flanked by two guard cells regulate its opening and closing The ground tissue in a leaf, called mesophyll composed of parenchyma cells sandwiched between the upper and lower epidermis 40
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Mesophyll A type of parenchyma tissue Two layers in dicots
Palisade mesophyll elongated columnar cells packed tightly together photosynthetic layer Spongy mesophyll irregular cells bound by air spaces loosely packed increases amount of surface area for gas exchange contains bundle sheath surround veins (vascular tissue) separates from rest of mesophyll
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(a) Cutaway drawing of leaf tissues
Dermal Ground Sclerenchyma fibers Cuticle Vascular Stoma Upper epidermis Palisade mesophyll Spongy mesophyll Figure 28.17a Leaf anatomy (part 1: cutaway drawing of leaf tissues) Lower epidermis Bundle- sheath cell Cuticle Xylem Vein Phloem Guard cells (a) Cutaway drawing of leaf tissues 42
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(b) Surface view of a spiderwort (Tradescantia) leaf (LM) Dermal
Guard cells Stomatal pore 50 m Epidermal cell (b) Surface view of a spiderwort (Tradescantia) leaf (LM) Figure 28.17b Leaf anatomy (part 2: surface view of a leaf of a spiderwort, Tradescantia, LM) Dermal 43
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(c) Cross section of a lilac (Syringa) leaf (LM)
Upper epidermis Palisade mesophyll Spongy mesophyll Lower epidermis 100 m Figure 28.17c Leaf anatomy (part 3: cross section of a leaf of a lilac, Syringa, LM) Dermal Vein Air spaces Guard cells Ground (c) Cross section of a lilac (Syringa) leaf (LM) 44
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Spines Tendrils Storage leaves Stem Reproductive leaves Storage leaves
Figure 28.7 Evolutionary adaptations of leaves Storage leaves Stem Reproductive leaves Storage leaves 45
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