Botany: Vascular, Ground tissues, secretory structures

What are vascular tissues?

- Interconnected network of cells and tissues that function for water and food transport
- Also transports hormones and signaling molecules

What does the vascular tissue compose of?

Xylem and Phloem

What is a xylem?

The tissue that conducts water in vascular plants

Aside from water, what are the function of xylems?

- Transport of solutes (translocation)
- For support
- For storage

Characteristics of the xylem cells?

Has thick, lignified cell walls

Where does the xylem given rise from and what type?

Procambium: primary xylem
Vascular cambium: secondary xylem

What are the three elements of the xylem?

Tracheary elements
Xylem fibers
Xylem parenchyma

What is the function of tracheary elements?

Conduction of water and transport of solutesW

What is the function of xylem fibers?

Supports the xylem tissue
Storage

What is the function of the xylem parenchyma?

Food storage
Translocation of various substances

What are the characteristics of the tracheary elements?

More or less elongated
Lignified secondary walls
Dead at maturity

What are the types of tracheary elements?

Tracheid
Vessel elements

What are the characteristics of tracheids?

Elongated and tapering
Several pits on common walls
Imperforate (no holes at the end)

What are the characteristics of vessel elements?

Wider than tracheids
Elongated but shorted
Perforated (connected end-to-end)
Evolves later than tracheids
Have perforations at the walls called perforation plates

What are the types of perforation plates?

Single - One large lacuna
Compound or multiple - several perforations

What are the types of compound perforation plates?

Pitted/foraminate/epheroid (circular perforations)
Reticular (net-like)
Scalariform (ladder-like)

What are the types of pitting patterns?

Scalariform - ladder-like series, pits are elongated horizontally
Opposite - oval bordered pits arranged horizontally, brick-like
Alternate pitting - pits are arranged in diagonal rows

What are the patterns of secondary wall formation?

Annular ring-like
Helical: spiral
Scalariform: ladder-like
Reticular: netted
Pitted: in areas without pitsW

What are the parts of a pit?

Torus - central thickened portion; impermeable
Margo - pit membrane around the torus in bordered pitsWh

What is cavitation?

The formation of cavities resulting from a breakage of water columns

What is embolism?

The blockage of conduit with air

What is air seeding?

External air is brought into the lumen of a dead cell from a cracked cell wall

What are the characteristics of xylary fibers?

Long cells with lignified secondary walls
Retain protoplast at maturityWh

What are the two types of xylary fibers?

Libriform
Fiber-tracheidWh

What are the possible appearances of xylem fibers?

Septate: Thin transverse walls
Gelatinous: Unlignified inner walls

What are the characteristics of xylem parenchyma?

Lignified secondary walls
Pit pairs may be bordered

What are the types of xylem parenchyma?

Axial parenchyma
Ray Parenchyma
Contact cellsW

What is an axial xylem parenchyma?

Elongated
Given rise by the fusiform initial

What is ray xylem parenchyma?

Given rise by the fusiform initialWh

What is xylem contact cells?

Parenchyma right next to the vessel elements
Gives rise to tylosesWha

What are the functions of tyloses?

Blocks the passage and spread of infectious materials
Prevents water leakage
Store resins, gums, and other ergastic substances

What is the primary xylem?

Xylem derived from the procambium

What is protoxylem?

- Earlier formed xylem
- Differentiates in parts of the primary plant that have not completed growth
- Few tracheary elements with annular/spiral thickenings
- Limited stretchabilityW

What is protoxylem lacunae?

Appears when a protoxylem are destroyedWh

What are the evidence that stretching occurs in mature protoxylem elements?

- Increase in distance between rings
- Tilting of rings
- Uncoiling of helicesW

hat is a metaxylem?

- Matures largely after elongation
- Wider tracheary elements and may contain fibers
- Tracheary elements with scalariform, reticulate, and pitted type of thickeningsW

What is centrarch?

Plants that possess a single vascular cylinder with the protoxylem at the center and is surrounded by the metaxylem

What is mesarch?

Protoxylem surrounded by the metaxylem Multiple vascular strands/bundles

What is endarch?

Metaxylems are developed to the exterior of the protoxylem

What is exarch?

Metaxylem is developed in the interior of the protoxylem

What is a fundamental tissue?

Tissues that are the foundation of the plant ontogenetically and phylogenetically

What are parenchyma cells?

* Tissues composed of **living cells**
* Varies in morphology and physiology

What are the general characteristics of the parenchyma?

* **Have living protoplast** at maturity
* Can resume meristematic activity
* **Totipotent -** can give rise to any other cell type
* **Have thin primary cell walls** - important for wound healing, regeneration, formation of adventitious organs, union of grafts
* **NO secondary walls**
* Non-lignified
* **Unspecialized morphologically and physiologically**

Are parenchyma cells considered meristematic cells?

Yes, only if they undergo dedifferentiation

Where do parenchyma cells originate, and what parenchyma cells do they associate with?

* **Ground meristem -** gives rise to the __pith, pith ray, cortex, mesophyll, and ground tissue of reproductive structures__
* **Procambium/vascular cambium -** Gives rise to the cells __associated with primary and secondary by the procambium and vascular cambium respectively__
* **Cork cambium -** Forms the __phelloderm__

What are the structures and appearances of the parenchyma cells?

* Isodiametric
* Lobed
* Irregular/branched
* Elongated

What are parenchyma chlorenchyma cells?

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* Cells that contain chloroplast that functions in photosynthesis
* Highly vacuolated with intercellular spaces
* Found in **mesophyll** in leaves

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What are parenchyma secretory cells?

* Cells responsible for secretions
* Contains __dense protoplast,__ rich in __ribosomes, numerous golgi bodies, and massively developed ER__
* Found in secretory ducts and secretory channels

What are the types of parenchyma storage cells?

* Starch-storing - abundant amyloplasts that contains starch with little intercellular storage
* Protein and oil-storing - Stores proteins and oil bodies in seeds
* Pigment-storing - contains **chromoplast and** **anthocyanin**
* Crystal-storing - stores **crystals** for defense in flowers and fruits
* Water-storing - Stores water in succulents

What are parenchyma transfer cells?

* Cells that contain **cell wall ingrowth** that **increases surface area** of the plasma membranes
* Transports solutes over short distances

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What are parenchyma aerenchyma cells?

* Characterized to have prominent **intercellular spaces**
* Common in angiosperms in aquatic/semi-aquatic habitats
* Spaces can be caused by lysogeny or schizogeny

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What are parenchyma idioblasts?

* Specialized cells that contain certain substances
* resin, crystals, oils, pigments, tannins, and excretory structures
* Have **different morphology** relative to the cells surrounding them
* Only one or two cells in one tissue that contain the substance, unlike storage cells with multiple tissues

What are collenchyma cells?

* Living cells composed of **less elongated cells with thick primary walls**
* A simple tissue - consists of ONE single cell type

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What are the characteristics of the collenchyma cells?

* **Living protoplast**
* **Uneven thickening of primary cell wall** because of uneven deposition of pectin and hemicellulose
* **Can resume meristematic activity** by removing cell wall thickening
* **Isodiametric (cross section) and elongated (longitudinal)**
* Found in **actively growing parts or regions** because of tis plasticity
* **Chloroplast is present**
* Primary cell walls are thick but **do are NOT lignified**

What is the function of the collenchyma?

A **supporting tissue** that retains the shape of the stem and its growing parts

Where do collenchyma cells originate?

* Ground meristem
* Procambium

Where are collenchyma cells distributed?

* Peripheral - beneath the epidermis
* Continuous - form a continuous ring periclinal to the surface
* Strand - axial strands separated by parenchyma, found as bundles
* Fascicular/perivascular - found near the periphery of the epidermal cells
* Supracribal - bordering the vascular bundle at the phloem side
* Infraxylary - bordering the vascular bundle at the xylem side
* Circumfascicular - surrounds the vascular bundle
* In stems as a continuous layer
* Rarely present in roots
* In leaves, found in major veins

What are the distribution of wall thickenings of collenchyma cells?

* Lamellar/plate - Walls on the sides are thicker than walls on the top and bottom
* Angular - Thickening is found in the sides or **corners** of cells
* Lacuna - similar to angular, but **air spaces** are present
* Annular - Uniform thickening of walls

What are the characteristics of sclerenchyma cells?

* Contains **lignified, secondary walls**
* May or may not retain protoplast at maturity
* Found in mature parts of plants

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What is the function of sclerenchyma cells?

For mechanical support - enable the organs to withstand strains from pressure, weight, stretching, and bending

What are sclerenchyma fibers?

* **Long, spindle-shaped cells**
* Contains **thick secondary walls**
* Supporting elements in parts that are **no longer elongating**
* Found in the xylem and more common in phloem

Where do sclerenchyma fibers originate?

* Procambium and vascular cambium
* Ground meristem
* Protoderm

What are the two groups of sclerenchyma fibers?

* **Xylary fibers** - fibers found in the xylem tissues; libriform (longer and thick-walled, lignified) and fiber-tracheid (shorter, thinner walls, less lignified)
* **Extraxylary fibers** - fibers located outside the xylem

What are the types of extraxylary fibers?

* **Phloem fibers** - starts as sieve-element; arise from primary phloem or as part of secondary phloem
* **Cortical fibers** - found and originate in the cortex
* **Perivascular fibers** - located in the periphery of the vascular cylinders
* **Bundle sheaths or bundle caps** - bundle sheath extensions (extend to the dermal tissues) and bundle cap (only found on the phloem)

What are sclereids?

* Arises from the **secondary sclerosis of parenchyma cells**
* Sclereids typically **are short cells with thick secondary walls**
* **Strongly lignified**
* **Provided with numerous simple pits**
* Retain **living protoplast**

What are the types of sclereids?

* **Astrosclereids**
* **Star-shaped, star-cells, with lobes or arms diverging from a central body**
* **Assumed to be for support**


* **Brachysclereids**
* **Stone cells, roughly isodiametric for strength and support**
* Thick walls made by many thin concentric layers
* **Macrosclereids**
* Elongated and rod-like
* Prevents desiccation, keep dormancy and deter herbivory
* **Osteosclereids**
* Bone-shaped
* Prevent desiccation, keep dormancy and deter herbivory
* **Trichosclereids**
* Hair-like branches projecting into intercellular spaces
* **Filiform**
* Longer slender cells

What are the origins of sclereids?

* Procambium
* Cork cambium
* Protoderm
* Ground Meristem

Where are sclereids distributed?

* Epidermis, ground tissue, and vascular tissues
* Not seen in most stems
* Most common in leaves
* **Terminal:** found at the ends of **small veins**
* **Diffuse:** sclereids dispersed throughout the tissue
* Found in fleshy regions of fruits

What is the phloem?

* Interconnected cells responsible for transfer of photosynthates
* The food-conducting tissue
* Information highways as it also transports hormones used for inter-organ communication
* Less sclerified
* Spatially associated with the phloem

Where does the phloem originate?

* Primary phloem - procambium
* Secondary phloem - vascular cambium

What are the sieve elements?

* Sieve-tube elements
* Sieve cells
* Companion cells
* Strasburger cells
* Parenchyma cells
* Sclerenchyma cells

How do sieve elements lose their organelles?

* **Selective autophagy -** disorganization/disappearance of most cellular components
* **Nuclear degeneration**
* **Pycnotic degeneration -** dense chromatin that ruptures nuclear envelope
* **Chromatolysis -** loss of sustainable contents that ruptures nuclear envelope

What are phloem sieve-tube elements?

* Only found in angiosperms
* Arranged in a vertical series to form **sieve-tubes**
* Associated with **companion cells**
* Contains **primary walls** with **sieve areas**
* Protoplast are living at maturity, but nucleus is absent

What are sieve areas?

Perforations on the primary walls made up of sieve pores

What are sieve plates?

Large sieve areas on the ends of sieve tube cells

What are the type of sieve plates?

* **Simple -** One sieve area on each end
* **Compound -** two or more sieve areas on each end

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What type of sieve plates do gymnosperms have?

Gymnosperms do not have sieve plates, but they do have sieve pores on each end

What are the types of callose?

* **Wound callose -** callose in sieve pores in response to mechanical injury
* **Definitive callose -** formed due to aging or senescence of sieve plates
* **Dormancy callose -** formed during times of dormancy; formed in the fall and removed in spring

What are p-protiens?

* Contained in the protoplast of sieve-tube elements
* Capable of forming a slime plug to prevent pathogen infection

What are the two types of plastids in the sieve-tube elements?

* p-plastid - protein-containing
* s-plastid - starch-containing

What are sieve cells?

* Found in gymnosperms and are less specialized
* Elongated and tapered at the end
* Lack companion cells, but have strasburger cells
* NO callose deposition
* NO sieve plates
* Protoplast is living, but NO nucleus
* NO p-proteins and s- and p- plastids

What are companion cells?

* **Nucleated life support system** for the sieve tubes in angiosperms
* Assists in giving ATP to the sieve-tub elements
* Elongated and smaller than the sieve-tubes
* Primary wall with living protoplast
* Neither sclerified nor lignified
* Collapse when sieve-tube dies

What are strasburger cells

* Like companion cells, but are for sieve cells in gymnosperms
* Numerous branched plasmodesmata
* Living at maturity with numerous cell components

Where are phloem parenchyma found?

* In the primary phloem and secondary phloem as axial parenchyma cells and ray parenchyma cells
* Cells in contact of sieve-tubes are NOT lignified, while those near fibers ARE lignified

What is the primary phloem?

The phloem initiated in the embryo that differentiates in thee procambium

What is the protophloem?

* The first functional food conducting tissue that is to be replaced by the metaphloem
* The precursory phloem cells in gymnosperms
* In angiosperms, these are narrow and inconspicuous

What is the metaphloem?

* Sieve elements that are longer and wider
* Companion cells are present
* Matures after growth in length
* Become inactive after secondary phloem differentiates

What is the secondary phloem?

* The phloem that differentiates from the vascular cambium

What are the two systems of the secondary phloem?

* **Axial system**
* includes the __sieve tube elements, companion cells, parenchyma cells and fibers__ in angiosperms
* Gymnosperms contain the __sieve cells and parenchyma cells__ only
* **Radial system**
* Composed of the __ray parenchyma cells risen by ray initials__
* Continuous with the xylem ray system
* in gymnosperms, the ray is __uniseriate and contain both parenchyma and strasburger cells__
* in angiosperms, __sclereids, secretory elements, and crystal-forming cells are present__

What causes a phloem to be non-conducting?

* Sieve elements may cease to function due to
* Sieve element breakdown
* Dilatation
* Sclerefication
* Formation of crystals
* Formation of definitive callose
* Tylosoids may invade the space of dead sieve elements
* Deposition or accumulation of crystals and tannins

What is secretion?

* The separation of substances from the **protoplast**
* Involves the removal of materials from the cells and accumulation fo secreted materials

What are primary metabolites?

* Metabolic
* Secretion that has a function involved in cell plant growth
* Hormones, enzymes, RNAs, sugars, photosynthates, amino acids

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What are secondary metabolites?

* Non-metabolic
* Non-functional, but still are used for defense and protection
* Alkaloids, terpene, tannins and resins, oxalate crystals

What are the two types of secretion?

* **Merocrine** - secreted without major damage to the secreting cell
* **Granulocrine** - attained through the fusion of secretory vesicles
* **Eccrine** - ions directly pass through the plasma membrane through active or passive diffusion
* **Holocrine** - secreted only upon degeneration or death of secretory cells

What are salt glands?

* Regulate the salt content of plant shoots
* An active process via holocrine secretion
* Secreted by trichomes in leaves and stems

What are hydathodes?

* Structures that **secrete dissolved substances** from the inside of the leaf to the surface known as **guttation**
* Caused by the **loose arrangement of parenchyma cells**
* The dew found on grass tips
* Can be **passive**
* Water is released from the tracheary elements, and passes through the intercellular spaces of the epithem to be secreted via the open stomata
* Can be **active**
* Water is actively exuded by secretory cells which are not connected to the tracheary elements

What are nectaries?

* Structures that **secrete nectar** through **stomatal pores and glandular trichomes**
* Cells may be restricted to the epidermis or may be several layers deep
* Includes the **alluring glands** of carnivorous plants
* May be **floral nectaries**
* Directly involved in sepals, petals, stamen, ovaries, or receptacle
* attract pollinators
* May be **extrafloral nectaries**
* Attracts insects that prey on or exclude the plant’s herbivores

What are colleters?

* The sticky secretions which dry and fall off
* Provide defense against insects and fungi by producing terpenes
* Emergence of the epidermis and NOT by trichomes

What are osmophores?

* Special glands that **secrete volatile substances**
* Known as **floral fragrance glands** that attracts pollinators

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What are glandular secretory structures?

* Functions as **deterrent from herbivores,** while some **attract pollinators**
* Lipophilic-secreting glands