Plant Tissues Midterms Reviewer PDF

Plant Tissues **1.Initials** (Meristem) - '*meristos*' meaning divided, unspecialized, undifferentiated, generate growth -cells that are actively engaged in cell division and responsible for the production of new cells. In the tip of the roots and stems. \*\*when an initial divides by mitosis, o...

Plant Tissues **1.Initials** (Meristem) - '*meristos*' meaning divided, unspecialized, undifferentiated, generate growth -cells that are actively engaged in cell division and responsible for the production of new cells. In the tip of the roots and stems. \*\*when an initial divides by mitosis, one daughter cell remains an Initial at the same location within the meristem, the other daughter cell called the [derivative] is pushed out of the meristem and either divides again or begins elongation and [*differentiation*- the process by which an unspecialized cell develops into a specialized cell]. Differentiation can sometimes be reversed [(from differentiated state to meristem again) this is called *dedifferentiation*]. This occurs during development of lateral meristem and in laboratory tissue culture. Types: a\. Apical meristem- responsible for the increase in length of stems and roots; 3 zones: protoderm, ground meristem, and procambium. b.Lateral meristem or cambia- responsible for the increase in width or diameter of stems and roots. \- Dicots generally have cambia but monocot does not. 2 types: vascular cambium, cork cambium. c.Intercalary meristem- responsible for further lengthening of stems and leaves far away from the tips of stems. **2. Permanent tissue**- tissues that attained their mature form and perform specific functions; derived from meristematic tissues. Could be simple or complex. A.*Simple* consist of only one kind of cells. **Dermal Tissue-**begins as parenchyma cells, that *protect the plant from physical damage and dessication*; help to *control the exchange of gases*. [Epidermis]- an external tissue; consist of single layer of living cells; appear cubical or rectangular; consist of ordinary epidermal cells and [*guard cells*- are kidney-shaped cells] which occur in pairs and bound [tiny openings/ pores called *stomata*]*. In plants that live more than one growing season, the epidermis of stem and roots is replaced by [ protective tissue called periderm].* [hair-like extensions called *trichomes*]. A *cuticle,* a layer outside the cell wall composed of wax and fatty substance called [*cutin* which *helps limit water loss.*] **Ground Tissues** [Parenchyma]- an internal tissue that has uniformly thin (contain less cellulose) cell walls, large intercellular spaces*;* spherical, many sided. Form Greek word *[parenchein]* means 'to pour in beside'. Function: *for food manufacturing and storage* Chlorenchyma- the specialized parenchyma. [Collenchyma]- slightly rectangular, elongated, compactly arrange; unevenly thickened (has thick cellulose layer) cell walls. Form Greek word *kolla*, meaning 'glue' Function: *provide flexible support*; *for food storage* \*\*[both parenchyma and collenchymas become ***turgid***] (swollen,enlarged) as a result of being full of water, to provide support. [Sclerenchyma]- irregular, commonly known as stone cells; dead when mature ; appear in the form of fibers/sclereids; secondary cell walls is hardened w/ **lignin** Function: *strengthening or supportive tissue* (provide rigid support) ***Fibers-*** elongated, thickened (in stem, tree trunks); ***Sclereids***-cubical, spherical (in nutshells, fruit pits; gritty, sandlike pieces in pear) **B.*Complex*** tissues consisting several kinds of cells **Vascular Tissue** [Xylem-] transport water and minerals from the roots to the leaves. 2 conducting cells: - *tracheids-* long cells w/ tapered ends, water-conducting cells; dead at maturity; thick 2^o^ cell wall; also has thinner regions called pits - *vessel elements-* transport water and minerals more rapidly than tracheids; dead when mature; wider, shorter, less tapered [Phloem]- transport sugars and other organic materials from leaves to roots 3 conducting cells: - *sieve-tube elements -*remain alive and active at maturity; conduct organic nutrients - *sieve plate-* cell wall of sieve tubes w/ membrane-lined pores that allow materials to pass from cell to cell w/out crossing the plasma membrane and cell walls - *companion cells-* adjacent of sieve tube, has nucleus that can supply proteins for sieve tube when mature [the contents transported by xylem and phloem is called **sap**] Plant Organs **Organ** - is consists of several types of tissues adapted as a group to perform particular function *Root System* - consists of all the roots; belowground *Shoot System* - consists of stems, leaves, and reproductive structures; aboveground Shoot - any individual stem and its leaves, any reproductive structures. A [shoot that has leaves but no reproductive structures is called ***vegetative shoot.***] **Embryonic 'organs'/structures:** 1.Cotyledons- 'seed leaves'; the largest most visible part of the embryo; thickened or fleshy; store food for the germinating seed 2\. Radicle- the embryonic root 3\. Plumule- embryonic shoot; give rise to epicotyl;portion of the embryonic stem located over the cotyledon 4\. Hypocotyl- embryonic stem; under the cotyledon and above the radical Endosperm- a storage tissue that surrounds the embryo; provide nourishment to the developing embryo Germination- the process of sprouting; initiated by temperature, water, light by triggering production of hormone Monocots- orchids, lilies, palms, onions, grass family Dicots- beans, peas, sunflowers, roses, oak tree **Annuals-** plant that completes its life cycle during a single growing season Ex. Marigolds, beans, corn **Biennials**- requires two growing seasons to complete its life cycle; typically herbaceous Ex. Carrots, beets, cabbage **Perrennial**- a plant that grows for many years **Roots** \- Anchor a plant in the ground and absorb water and dissolved nutrients from the soil \- produce hormones and other substances that regulate plant's development and structure Types: 1.Taproot \- Has lateral roots \- For dicots and gymnosperm 2\. Fibrous root (Adventitious) \- For monocots and seedless vascular plants Root Cap - protects cells of the root apical meristem as the root pushes between soil particles - produce *mucigel* (slimy polysaccharide that lubricates the passage of root through the soil) D:\\MARA FILES\\biology\\PLANT organs\\root (1).gif **Specialized Roots** Buttress- on bigger forest trees Climbing aerial roots- orchids Pneumatophores (air roots)- mangroves Contractile roots- in lilies Parasitic Roots (*Haustoria*)  **Stem** - produce leaves, branches and flowers; hold leaves up in the sunlight - transport substances between roots and leaves Parts: 1. Nodes- where leaves are attached 2. Internode- regions between the nodes 3. Buds- contain undeveloped tissue that can produce new stems and leaves **Monocot Stems** **Dicot Stems** -vascular bundles are scattered throughout -vascular bundles are arranged in a the stem cylinder/ringlike -phloem faces the outside, xylem faces -[parenchyma cells inside this ring is] the center [called as **pith**] -distinct epidermis -ground tissue consist mainly of parenchyma **Primary Growth of Stems**- the increase *in length;* produced by cell divisions in the apical meristem; takes place in all **seed plants.** **Secondary Growth of Stems-** the increase *in width;* takes [place in lateral meristematic tissues called the vascular cambium and cork cambium]; for **conifers and dicots**. **Vascular cambium**- type of lateral meristematic tissue that produces vascular tissues and increases the thickness of stems over time. **Cork cambium-** produces the outer covering of stems a. Formation of the Vascular Cambium- giving rise to new layers of xylem and phloem resulting to a wider stem\-\--continuous production of vascular tissues will result to a thicker stem b. Formation of Wood*(layers of xylem)*- as woody stems grows thicker, the older xylem near the center of stem no longer conducts water but become a **heartwood-**usually darkens w/ age. **Sapwood** surrounds the heartwood which is active in fluid transport and therefore lighter in color. c. Formation of Bark- include all of the tissues outside the vascular cambium (phloem, cork cambium, cork) **Modified Stems** Tuber- a stem usually growing underground that stores food. Ex. Potato Bulb- made up of a central stem, surrounded by a short thick leaves. Ex. Onion Corn- looks similar to the bulb but is a thickened stem that stores food Rhizome- a horizontal, underground stem. Ex. Stem of a ginger Stolon- in strawberries **Leaves** -Photosynthesis aided by specialized ground tissues: *mesophyll* (palisade, spongy), *stomata* that allow CO2 and O2 to diffuse in and out of the leaf, *guard cells* that control the opening and closing of stomata. -Transpiration-is the loss of water from a plant through its leaves -Gas Exchange Development - From leaf primordia that emerge from shoot apical meristem---leaf buttress - Petiole- has 2 small leaflike flaps called *stipule* that are attached at the node. - Blade *Margin*-edge of leaf blade Some leaves known as sessile, lack petiole and are attached directly to stem. Venation-veins pattern (parallel, netted) Internal Morphology Epidermis - protects the leaf from water loss, abrasions, and the entry of fungi and bacteria that cause disease - Regulates exchange of gases (by trichomes) - stomata and guard cells- where exchange of gases and transpiration happens. Mesophyll - Chlorenchyma ground tissue - *mesos* (middle); *phyllon* (leaf) - carry out photosynthesis (in palisade) - Palisade and Spongy Vascular Tissue (leaf vein) - Netted venation- dicots and ferns - Parallel venation- monocots and gymnosperm Forms under the influence of auxin. Types: Simple Leaf - Consist of single, undivided blade; deeply lobed Compound Leaf - The blade is divided into leaflets **Deciduous plant-** those that lose their leaves at certain seasons of the year (maple and sycamore); have *abscission zones*- an area where the leaves separate from the plant Modified Leaves: Bract- in poinsettia Tendril Spine *Hydangea macrophylla* Window leaves- in cacti species Venus flytrap- insect-eating leaf Pitcher leaf Prickles- in *Solanum hirtum* Floating leaves - in lilies; stomata are in the bottom Drought-tolerant leaves - of xerophytes in the dessert **Reproductive Structures** **Cones/Strobili** \- in Gymnosperm - have spore-producing leaves called *sporophyll* that produce *sporangia---spore---gametophyte* ***Flowers*** - in Angiosperm (258,000 species) - bear enclosed seeds - [stamen (male)]; [carpel (female)] - monoecious; dioecious Parts: 1\. Peduncle - stem/ base of the flower 2\. Receptacle - swollen tip of peduncle w/c bears other floral parts 3\. Sepals (calyx) - protect the flower bud before it opens 4\. Petals (corolla) -- colorful; attract pollinators 5\. Stamen (androecium) - pollen-producing/ male part; has 2 parts: *filament, anther* (pollen sac) Carpel (gynoecium)- the ovule-bearing/ female part Composed of: a\. Stigma- provides sticky surface for pollen b\. Style- connecting stigma and ovary c\. Ovary- contain one or more ovules *Inflorescence* - group of flowers a. Panicle e. Corymb b. Spike f. Simple Umbel c. Raceme g. Compound Umbel d. Catkin h. Composite/head *Flowers could be:* Complete- contain all parts Incomplete- lack one or more parts Perfect- if monoeciuos/bisexual Imperfect- if dioecious/unisexual Regular/actinomorphic- radial symmetry Irregular/zygomorphic- bilateral symmetry Growth and Development **Life Cycle of Gymnosperms** -takes place in cones where seeds are located: a.)pollen cones b.)seed cones a.**)Pollen cones**- also called male cones that produce the male gametophytes which are called *pollen grains* b.)**Seed cones**-where *ovule* is located that produce female gametophytes; larger than pollen cones **Pollination**- takes 2 years to complete---as male cone release enormous numbers of pollen grains which then carried by the wind--- **Fertilization and Development-** if a pollen grain lands near an ovule, the grain splits open and begins to grow a structure called a *pollen tube*---once the pollen reaches the female gametophyte, one sperm nucleus disintegrates, and the other fertilizes the egg contained within the female gametophyte\-\-- **Life Cycle of Angiosperms** -takes place within the flower **Pollination**- most angiosperms are pollinated by animals (insects, birds, bats) **Fertilization**- occurs by a *double fertilization* between male and female gametophyte. First, one of the sperm nuclei fuses with the egg nucleus to produce a diploid zygote---the zygote will grow into a new plant embryo. Second, the other sperm nucleus fuses with two sperm nuclei in the embryo sac to form a triploid cell---this cell will grow into a food-rich tissue known as **endosperm** which nourishes the seedling as it grows. ***Seed Dormancy***- a period of time during which a plant embryo is alive but not growing. Environmental factors such as temperature and moisture can cause seed to end dormancy and germinate. ***Seed Germination***- is the early growth stage of the plant embryo **Fruits** - Protects the developing embryo (seeds) from drying out - Protect from disease and herbivores - promote seed distribution - provide ready-made fertilizer for the germinating seed **Parts:** 1. Pericarp -- consists exocarp (skin), mesocarp, endocarp **Types:** 1. Simple - developed from one carpel/ fused carpels 2. Aggregate -- originate from one flower that has many 3. Multiple -- from carpels of more than one flower in a single ***Simple fleshy fruits** --* one or more layer of pericarp become soft during ripening 1\. Berries- may originate either from one carpel or several carpels; may have 1/multiple,seeds Ex. Tomatoes, grapes, bananas, guava, mangosteen, blueberries, cranberries 2.Hesperidia -- w/ leathery skin or exocarp that produces pungent, acidic oils; inner ovary produces sacs that fill w/ juice *Include*:Grapefruit, Lemons, oranges, limes, tangerines, kumquats, grapefruit 3\. Pepos - has thick rind/ exocarp; mesocarp and endocarp may not be distinc; a modified berry *members*: Pumpkin ,Watermelon, Cantaloupes, Cucumber, squashes 4\. Drupes -- develop from flowers w/ Superior ovaries and one ovule; has hard endocarp known as pit, attached to a single seed Ex.Olives, Almonds, coconuts, avocado,peaches, cherries 5\. Pomes -- resemble berries but the bulk of the fleshy fruit comes from an enlarged receptacle Ex. Apples , pears  ***Simple dry fruit*** - are either dehiscent or indehiscent [*dehiscent* -] splits open at maturity to shed seeds 1.Follicles- have single carpel that split along one seam to release seeds Ex.Milkweed, Columbine, magnolias 2\. Legumes -- at maturity, has two seams that split the fruit into two halves Legume family (*Fabaceae*): beans, peanuts, peas 3\. Siliques -- consist of two carpels that split into two halves, with the seeds found on a central partition within the halves Mustard family (*Brasicaceae*): Shepherd's purse, Cabbage, radish 4.Capsules -- develop from two carpels; split along the seams between the carpels or split within carpel Ex. Poppies, Irises, Orchids, Yucca, snapdragons Indehiscent -- remain closed at maturity 1.Nuts- have stony pericarps as shell; originate from compound carpels Ex: Acorns, Hickory nuts, Chestnut, hazelnut 2\. Schizocarp- have hard, thin pericarp which opens into two or more parts Parsley family (*Apiaceae*): Parsley, Carrots ,Celery, Maple (Aceraceae) 3\. Achenes -- attached to pericarp at the root end; form from single carpel Ex: Sunflower, buttercups 4\. Samaras -- w/ hard, thin, elongated pericarps that produce wings around the single seed Ex: Ash and elm trees 5\. Caryopses (singular, *caryopsis*)- grain; has dry, hard pericarp Members of grass family (Poaceae): Corn, rice Plant Hormones **Hormones** \- Organic compounds produced in low concentration in one part (source) of plant and transported to another part (target) \- Cause physiological or developmental responses \- Also called plant growth regulators 1. **Promoters of Growth** - ***Auxin***- from '*auxein'*, to increase by Fritz Went 1926. ex. Indoleacetic acid (IAA); involved in the response of stems to gravity. Made from amino acid and bases synthetic auxins: Napthaleneacetic acid (NAA)- [to stimulate and inhibit growth] 2,4-dicholorophenoxyacetic acid (2,4=D)- used as weed killer - ***Gibberellins*-** ex. [Gibberellic acid] (GA) GA3- present in newly developing plant organs; from a fungus- *Gibberella fujukuroi (*linking five-carbon isoprenoid units*)* - ***Cytokinins (**from cytokinesis**)***- derivative of purine adenine. ex. ***Zeatin**-* extracted from corn kernels*;* used in plant tissue cultures for production of shoot buds; made from amino acids and bases 2. **Growth Inhibitors** - ***Ethylene (***gas)- combustion product of kerosene; initiate a growth [maneuver called **triple response**]: a. Slowing of stem or root elongation b. a thickening of the stem or root c. curving to grow horizontally - ***Abscisic acid (ABA)***- stress hormone; synthesized in leaves, stems, roots, and green fruits - **Signal-transduction pathway**- series of events that stimulates or inhibits cellular response to hormone; consists of molecule (proteins, ions) interaction. Plant Responses **Tropism**- growth responses/movement to external stimuli **1.Phototropism**- it in response to light stimulus; [Blue light] absorption controls the growth of stems and the opening of stomata. *Phototropin*- flavin-containing protein that absorbs blue light. Absorption of red and far-red light determines when seed germination, stem and root growth, and flowering occur. This is initiated by *Phytochrome-* absorbs red light. Photomorphogenesis- the effect of light on plant growth and development Photodormant seeds- requires light for dormancy activation Positive phototropism- growth towards light Negative phototropism- growth away from light **2. Gravitropism -- response to gravity.** Positive gravitropism- root grow *toward gravity*; Negative gravitropism- when shoot grow *away from gravity* **3.Thigmotropism**- a mov't in response to touch (ex. Tendrils curl around objects they encounter because of a touch response. **4.Photoperiodism-** a physiological response prompted by changes in the length of day and night **SDP**- short- day plant; plants that flower only when the day length is shorter than a critical length. **LDP**- long-day plant ; flowers only when the day length is longer than critical **DNP**- day-neutral plant; flowers regardless of the day length. Other observable tropisms require further study: - Hydrotropism- growth towards or away from water - Heliotropism- or sun tracking; flowers or leaves that either follow the Sun or avoid the Sun throughout the day - Chemotropism- growth toward or away from a chemical stimulus Plant Nutrition **soil layers, minerals, soil solution, rhizosphere, nutrients** **Soil** - composed of mineral and organic matter - supports life - interaction of biotic and abiotic occur - has lichens, algae, mosses that supports the growth of bacteria and fungi **Types:** **Organic Soil** **- has greater than 12-20% organic carbon content** **Mineral Soil** **- has less than 12-20% organic carbon content** **organic acid excreted by microorganisms promote the dissolution of rock into smaller particles** **Surface soil \--Subsurface \--Rhizosphere \--Deep Soil** - **The rate of development of a typical soil profile is usually very slow (2000-20,000 yrs.)** **Profile - vertical cut of soil body** **Horizon -- layer; has its own thickness, consistency, composition and chemistry** **Horizon O** **- organic/surface layer** **- consist of partially decomposed organic material** **Horizons A, E, B, C - mineral layers** **A - zone of maximum biological activity** **Soil Solution** **water + dissolved materials** **either:** - **well drained - has higher oxygen concentration** - **waterlogged soil -- lower oxygen concentration; can become anoxic quickly** **Nutrient Status** - **organic-rich surface layers, around the rhizosphere** - **in some soil, the availability of phosphorus and nitrogen limit microbial productivity.** **Rhizosphere** - **area around the roots of plants** - **nitrogen fixers and nitrifying bacteria are concentrated** - ***Nitrosococcus, Nitrosolobus, Nitrospina, Cyanobacteria* are common** **17 chemical elements** - **Macronutrients- elements that are used in large amounts for producing the body of the plant and for carrying out essential physiological processes** - **Micronutrients- necessary cofactors for enzymes and are therefore recycled by the plant.** **Cl, Fe, B, Mn, Zn, Cu, Mo, Ni** **Nitrogen Fixation- the conversion of nitrogen gas into nitrate or ammonium** **Some nitrogen --fixing bacteria are free-living but most form mutualistic associations with certain plants (legumes- in root nodules) which then add nitrogen back to the soil. Legumes take less nitrogen from the soil.**