7: Köklər və suyun hərəkəti - Kök quruluşu və anatomiyası - Biologiya

270 milyon illik daşlaşmış ağac qıjı

Təxminən 300 milyon il əvvəl Karbon erasında yer üzündə nəhəng likopodlardan (Lycophyta bölməsi), horestaillərdən (Sphenophyta bölməsi) və ağac qıjılarından (Pterophyta bölməsi) ibarət geniş meşələr üstünlük təşkil edirdi. Yer kürəsinin kömür ehtiyatlarının çoxu bu dövrə aid kömürləşmiş bitkilərin kütləvi yataqlarından yaranmışdır. Braziliyadan gələn daşlaşmış gövdələr təxminən 270 milyon il əvvəl, dinozavrların yaşından əvvəl yaşamış nəsli kəsilmiş ağac qıjısının ( Psaronius brasiliensis ) hüceyrə təfərrüatlarını ortaya qoyur. Psaroniusun daşlaşmış gövdəsində iynəyarpaqlılara və ikibucaqlı angiospermlərə xas olan konsentrik böyümə halqaları yoxdur. Bunun əvəzinə, ksilem toxumasının damar paketlərini təmsil edən çoxsaylı qövslərdən ibarət mərkəzi stele var. Sapı əhatə edən yarpaqların əsaslarıdır. Həyatda Psaronius, yəqin ki, Yeni Zelandiyanın indiki Cyathea ağac qıjılarına bənzəyirdi.

Bitkilərdə suyun sorulmasının növləri

Bitkilər adətən aşağıdakı iki üsulla suyu udur:

Suyun aktiv udulması

Bu cür su udulması, tənəffüs kimi metabolik fəaliyyəti yerinə yetirmək üçün kök hüceyrələri tərəfindən metabolik enerjinin xərclənməsini tələb edir. Bitkidə aktiv udma iki yolla baş verir, yəni suyun osmotik və qeyri-osmotik udulması.

1. Suyun osmotik aktiv udulması: Bu tipdə suyun udulması osmoz vasitəsilə baş verir, burada su kök hüceyrəsinin konsentrasiya qradiyenti ilə kök ksileminə keçir. Osmotik hərəkət hüceyrə şirəsində məhlulun yüksək konsentrasiyası və ətrafdakı torpağın az konsentrasiyası ilə əlaqədardır.
2. Suyun qeyri-osmotik aktiv udulması: Burada suyun udulması suyun hüceyrənin konsentrasiya qradiyenti əleyhinə torpaqdan hüceyrəyə daxil olduğu yerdə baş verir. Bu, tənəffüs prosesi vasitəsilə metabolik enerjinin xərclənməsini tələb edir. Deməli, tənəffüs sürəti artdıqca suyun udulma sürəti də artacaq. Auxin böyümə tənzimləyici hormondur, bitkilərdə tənəffüs sürətini artırır və bu da öz növbəsində suyun udulma sürətini artırır.

Suyun passiv udulması

Bu cür su udulması metabolik enerjinin istifadəsini tələb etmir. Absorbsiya transpirasiya kimi metabolik fəaliyyətlə baş verir. Passiv udma, suyun udulmasının transpirasiya çəkməsi ilə olduğu bir növüdür. Bu, suyun yuxarıya doğru ksilem şirəsinə keçməsinə kömək edən gərginlik və ya qüvvə yaradır. Transpirasiya dərəcəsi daha yüksəkdir və suyun udulması daha yüksəkdir.

Suyun udulmasında kök tüklərinin rolu

Kök bəzi boruşəkilli, tük kimi və birhüceyrəli strukturlardan ibarətdir Kök tükləri. Kök sistemində kök tüklərinin çıxdığı bölgəyə deyilir Kök saç zonası. Kök tüklərinin zonası su udma fəaliyyətində iştirak edən yeganə bölgədir. Kök saç zonası su keçirən bölgədir. Kök tükləri epidermis adlanan təbəqədən əmələ gələn tüklərdir çubuqlu təbəqə.

Kök tüklərinin hüceyrə divarı ikiqat membrandan ibarətdir. Pektin xarici təbəqədə, sellüloza isə hüceyrə divarının daxili təbəqəsində mövcuddur. Hüceyrə divarının altında seçici keçiricilik var sitoplazmik membran. Hüceyrə və ya sitoplazmatik membran xüsusi maddələrin hüceyrə konsentrasiyası gradientindən keçməsinə imkan verəcəkdir.

Sitoplazmatik membranın içərisində kök hüceyrələri, nüvə və vakuol və ya hüceyrə şirəsi mövcuddur. Torpaq aqreqatlarında kök tükləri tərəfindən müxtəlif mexanizmlər vasitəsilə kök ksileminə daşınan kiçik su damcıları var ki, bunlardan osmos ən çox yayılmışdır.

7: Köklər və suyun hərəkəti - Kök quruluşu və anatomiyası - Biologiya

ÇİÇƏKÇİLƏN BITKININ MORFOLOGİYASI VƏ ANATOMİYASI Aşağıdakı veb-səhifə Bitkilərin Biologiyası (BOT 1103) mühazirə kursunun birinci hissəsində verilən mühazirələrin əsasını təşkil edən qeydlərimin surətini təqdim edir. Zəhmət olmasa, öz qeydlərinizə, paylama materiallarına və dərsliyə müraciət edin (Stern, K., R., JE Bidlack, and SH Jansky. 2008. Introductory Plant Biology, McGraw-Hill. 616 s. - oxu tapşırıqları proqramda var) əlavə məlumat üçün. Bu veb-səhifəyə semestr ərzində alacağınız müxtəlif paylama materiallarında və əlaqəli materiallarda (məsələn, filmlər, diaqramlar, ümumi proqnozlar və s.) olan məlumatlar daxil deyil. Siz də bu məlumat əsasında qiymətləndiriləcəksiniz. Aşağıdakı sənəddə hər hansı bir səhv qeyd etsəniz, bunu diqqətimə çatdırsanız çox şad olaram. E-poçt ünvanı: [email protected]

KÖKLƏR: Təşkilat və Anatomiya

1. Funksiya
2. Xarici anatomiya
3. Daxili anatomiya
4. Xüsusi köklər
5. Köklər və bitki qidası

• Köklər bitkini substratda və ya torpaqda lövbərləyir.
• Köklər normal böyümə, inkişaf, fotosintez və çoxalma üçün lazım olan suyu və həll edilmiş qidaları və ya həll olunan maddələri (azot, fosfor, maqnezium, bor və s.) udur.
• Bəzi bitkilərdə köklər xüsusi funksiyalar üçün uyğunlaşdırılmışdır, bu da bitki kökləri haqqında bölmənin sonunda müzakirə ediləcəkdir.

1. Kök qapağı
2. Hüceyrə bölünməsi bölgəsi
3. Uzatma bölgəsi
4. Fərqlənmə və ya yetkinləşmə bölgəsi

• Kök qapağı
  • hər bir kökün ucunda parenxima hüceyrələrinin yüksük şəkilli kütləsi
  • kökü mexaniki zədələrdən qoruyur
  • Diktiosomlar və ya Golgi cisimləri selikli sürtkü (mucigel) buraxır.
  • hüceyrələr bir həftədən az davam edir, sonra ölür
  • cazibə qüvvəsinin qavranılmasında əhəmiyyətli ola bilər (yəni, geotropizm və ya qravitropizm)
  • amiloplastlar (həmçinin statolitlər adlanır) hüceyrələrin dibində yığılmış kimi görünür, ola bilsin ki, bitkinin nişasta ilə yüklü orqanellələrin bu çöküntüsünü hiss etməsi və bunu aşağı istiqamət kimi şərh etməsi mexanizmi var.
  • Apikal meristem - hüceyrələr gündə bir və ya iki dəfə bölünür.
  • Keçid meristemləri kök və tumurcuqların uclarından əmələ gəlir. Bunlara daxildir:
    • protoderm (epidermi əmələ gətirir)
    • torpaq meristemi (yer toxumasını əmələ gətirir)
    • prokambium (ilkin floem və ksilem əmələ gətirir).
    • hüceyrələr daha uzun və geniş olur
    • root hairs develop as protuberances from epidermal cells
    • increase the surface area for the absorption of water
    • cuticle exists on root but not on root hairs
    • A. epidermis (outermost layer of cells forming the initial covering on a root).
    • B. cortex (ground tissue that surrounds the vascular cylinder or stele).
    • C. endodermis with Casparian strip (regulates the flow of water and dissolved substances).
    • D. primary xylem (water-conducting tissue found in the vascular cylinder or stele)
    • E. primary phloem (food-conducting tissue found in the vascular cylinder or stele)
    • The ring of cells beneath the endodermis would be the pericycle (the origin point for the production of lateral roots)
    • The band of tissue between the phloem and xylem are remnants of procambium which could lead to the production of the vascular cambium and secondary growth, especially in a woody dicot root.

    

    • Food storage (Carbohydrates)
      • manioc or cassava => the source of starch for making tapioca pudding
      • sugar beets => sucrose
      • Historical FYI: the original Jack O'Lanterns were carved out of rutabagas, turnips, and white potatoes. Americans introduced the practice of using the pumpkin of this purpose.
      • velamen roots of orchids: a thick epidermis to prevent water loss.
      • prop roots of corn for support
      • adventitious roots of ivies, aid in climbing
      • mycorrhizae or "fungus roots" where a symbiotic relationship forms between a plant and a fungus. In this partnership the fungus provides protection against some types of pathogens and increase the surface area for the absorption of essential nutrients (e.g. phosphorous) from the soil. The plant in return provides food for the fungus in the form of sugar and amino acids.
      • Legumes (e.g., pea, beans, peanuts) form root nodules. Mutualism between a plant and bacteium which allows for the fixation of atmospheric nitrogen to form that the plant can utilized. The bacterium is reward with food and a place to live

      V. ROOTS AND PLANT NUTRITION

      • Plants require large amounts of carbon, hydrogen, and oxygen. Majority arrives to the plant in the form of carbon dioxide and water.
      • Other elements are essential for growth include the macronutrients and micronutrients.
      • Soil is the source of minerals or nutrients used by plants.
      • nitrogen (proteins, nucleotides)
      • phosphorous (ATP, nucleic acids)
      • potassium (movement of materials across membranes)
      • calcium (associated with increasing sensitivity of tissues to different plant hormones)
      • magnesium (chlorophyll, assists functioning of certain enzymes).
      • sulfur (component of cysteine, an amino acid. sulfide bonding in proteins).
      • iron (electron transport system in photosynthesis and respiration)
      • boron
      • manganese
      • sink
      • copper (cytochromes in electron transport systems)
      • molybdenum (necessary for normal functioning of nitrate assimilation)
      • chlorine
      • For example, sodium/chlorine causes wilting (salt run off from streets that are treated to remove ice).
      • Excessive amounts of boron, copper, manganese, aluminum are toxic to plants.
      • Plant nutrition is linked to the chemical and physical attributes of the soil the plant is growing in.
      • Soil Particles - SAND, SILT, and CLAY - mix some soil in a jar with water, and allow it to settle out overnight. The sand will be on the bottom, the silt will be next, and the clay will be on top. Clay is the final product of weathering and is composed of the smallest particles. Loams contain approximately equal amounts of sand, silt, and clay. Cation exchange from the surface of negatively-charged clay particles to the plant is facilitate by trading a cation for a hydrogen ion. Anions do not attach to clay and are frequently leached from the soil before the plant can obtain them (sulfates and nitrates).
      • Humus is the decomposing organic matter in soil. Amount varies along a continuum MINERAL SOILS (1-10% humus) To ORGANIC SOILS (about 30 % humus).
      • Air -About 25-50% of the volume of soil is air. The amount of air is higher in sandy soils than in clay soils.
      • Water - Soil contains chemically bound (locked to minerals and clay particles - unavailable to plants) and unbound water (available to plants).

      STEMS: Organization and Anatomy

      • Stems support leaves and branches.
      • Stems transport water and solutes between roots and leaves.
      • Stems in some plants are photosynthetic (e.g., cacti - leaves are reduced to spines to protect against herbivory and reduce water loss).
      • Stems may store necessary materials for life (e.g., water [cactus, miscellaneous succulents] starch, sugar [sugarcane]).
      • In some plants, stems have become adapted for specialized functions, which will be discussed at the end of the section on plant stems.

      REFER TO FOLLOWING DIAGRAM OF A WOODY DICOT STEM:

      FYI: Apical dominance refers to the suppression of growth by hormones produced in the apical meristem. The Christmas tree pattern of pines indicates strong apical dominance. Bushy plants have weak apical dominance. If apical meristem is eaten or destroyed, plants may become bushy.

      III. INTERNAL ANATOMY IN FLOWERING PLANTS

      Dicotyledon (two seed leaves) and Monocotyledon (one seed leaf) flowering plants.

      • no vascular or cork cambium (secondary growth is rare)
      • vascular tissue in bundles (primary phloem, primary xylem, procambium, and sclerenchyma fibers) and distributed randomly through the ground tissue
      • ground tissue not divided into pith and cortex
      • intercalary meristems at base of nodes allow for elongation of stem (e.g., grass, bamboo) among some monocots
      • some secondary growth may or may not develop
      • vascular tissue in bundles (primary phloem, primary xylem, procambium, and sclerenchyma fibers) but arranged in a circular pattern when stem is observed in cross section
      • ground tissue is divided into pith and cortex
      • woody dicot stems start out like that in herbaceous dicots, but these develop secondary growth
      • lateral meristems allow the stem to increase in girth or diameter
      • lateral meristems: vascular cambium and cork cambium (phellogen)
      • Further discussion of secondary growth appears in a later section on secondary growth.
      • Rhizomes - horizontal stems that grow below the ground with adventitious roots examples are irises, grasses.
      • Stolons or runners - horizontal stem that grows above the ground with long internodes examples are strawberry, airplane plants.
      • Tubers - accumulation of food at the tips of underground stolons, after the tuber matures the stolon dies, the "eyes" of a potato are the nodes of a starch-ladened stem.
      • Rosette - stem with short internodes and leaves attached at nodes
      • Bulbs - large buds with a small stem at the lower end surrounded by numerous fleshy leaves, adventitious roots at base examples include onion, tulip, lily.
      • Corms - resemble bulbs but composed entirely of stem tissue surrounded by a few papery scale like leaves, food storage organs with adventitious roots at the base of corms examples include crocus and gladiolus.
      • Cladophylls - leaf-like stems examples include butcher's broom, asparagus.
      • Cacti - stout fleshy stems that are modified for food and water storage and photosynthesis.
      • Thorns - honey locust (modified stem), black locust and some species of Eyforbiya ( spines are stipules), roses (thorn or prickles arise from epidermis).
      • Tendrils - for climbing for example, grape and Boston ivy (English ivy - adventitious roots not stem).

      SECONDARY GROWTH IN STEMS AND ROOTS In woody plants, most of which are dicots, secondary growth may occur in the roots or the stems. As the plant develops functional lateral meristems, that is, the vascular cambium and cork cambium (the phellogen), the diameter of roots and stems increases as new tissues are produced. This increase in girth causes irreparable damage especially to the epidermis, phloem, and associated tissues.

      Please refer to the flow charts of primary and secondary growth in stems and roots that were handed out in lab. Vascular cambium produces secondary phloem and xylem. The study of woody plant growth over time by examining the annual rings created by secondary xylem is known as Dendrochronology .

      Keep in mind that the periderm arises from the growth and production of cork (dead and suberized at maturity) and parenchyma (lenticels - allows for gas exchange) from the cork cambium . The periderm replaces the outer covering of the plant as it increases in girth. The bark includes the periderm and any other tissue (living or dead) from the outermost part of the tree to the cylinder of the vascular cambium in the stem and the root.

      LEAVES: Organization and Anatomy

      • Leaves are the solar energy and CO₂ collectors of plants.
      • In some plants, leaves have become adapted for specialized functions, which will be discussed at the end of the section on plant leaves.
      • Leaves possess a blade or lamina, an edge called the margin of the leaf, the veins (vascular bundles), a petiole, and two appendages at the base of the petiole called the stipules.
      • Arrangement of leaves on a stem = phyllotaxy.
        • whorled - three or more leaves at a node.
        • opposite - two leaves attached at the same node.
        • spiral or alternate - one leaf per node.
        • Simple leaf = undivided blade with a single axillary bud at the base of its petiole.
        • Compound leaf = blade divided into leaflets, leaflets lack an axillary bud but each compound leaf has a single bud at the base of its petiole.
          • pinnately-compound leaves: leaflets in pairs and attached along a central rachis examples include ash, walnut, pecan, and rose.
          • palmately-compound leaves: leaflets attached at the same point at the end of the petiole examples of plants with this leaf type include buckeye, horse chestnut, hemp or marijuana, and shamrock.
          • Netted-venation = one or a few prominent midveins from which smaller minor veins branch into a meshed network common to dicots and some nonflowering plants.
            • Pinnately-veined leaves = main vein called midrib with secondary veins branching from it (e.g., elm).
            • Palmately-veined leaves = veins radiate out of base of blade (e.g., oak, maple).
            • Epidermis = single layer of epidermal cells (containing no chloroplasts) that interlock with one another on the upper (adaxial - toward the leaf axis) and lower (abaxial - away from the leaf axis) side of the leaf blade the outer surface is often coated with a waxy substance called cutin to form the cuticle (to prevent excessive water loss) and the hair-like structures called trichomes.
            • In the epidermis are pores called stomata (pl.), stoma (singular), which allow for gas exchange. Stomata are formed by two guard cells, which regulate the opening and closing of such pores. In dicots, guard cells tend to be sausage-shaped, whereas in monocots, these tend to be shaped like a bone or a fattened capital letter I. Guard cells possess chloroplasts. When water is pumped into the guard cells, these tend to bend away from one another creating the opening when water is pumped out of these cells, the cells become more cylindrical in shape and the stomata close.
            • Beneath the upper layer of epidermis, are a rows of vertically-positioned chlorenchyma cells that form the palisade mesophyll. Just below this layer exists bag-like chlorenchyma cells that are loosely packed together which form the spongy mesophyll. The chloroplasts in these two layers of mesophyll are responsible for photosynthesis. Beneath the lower most portion of the mesophyll is the lower epidermis.
            • Veins = vascular bundles xylem (water-conducting tissue) oriented towards the upper side of the leaf, containing phloem (food-conducting tissue) oriented towards the lower side of the leaf, sclerenchyma fibers, and parenchyma tissue (which may form a bundle sheath surrounding the vein).
            • Collenchyma may be present in the midrib of the leaf or in the petiole just below the epidermis. Collenchyma serves as strengthening tissue to assist leaves in supporting their own weight and to prevent damage due to motion caused by the wind.
            • Many plants are deciduous (able to loose their leaves during cold or dry seasons).

            IV. SPECIALIZED LEAVES

            • Cotyledons: embryonic or "seed" leaves. First leaves produced by a germinating seed, often contain a store of food (obtained from the endosperm) to help the seedling become established.
            • Tendrils - blade of leaves or leaflets are reduced in size, allows plant to cling to other objects (e.g., sweet pea and garden peas ).
            • Shade leaves = thinner, fewer hairs, larger to compensate for less light often found in plants living in shaded areas.
            • Drought-resistant leaves = thick, sunken stomata, often reduced in size
              • In American cacti and African euphorbs, leaves are often reduced such that they serve as spine to discourage herbivory and reduce water loss stems serve as the primary organ of photosynthesis.
              • In pine trees, the leaves are adapted to living in a dry environment too. Water is locked up as ice during significant portions of the year and therefore not available to the plant pine leaves possess sunken stomata, thick cuticles, needle-like leaves, and a hypodermis, which is an extra cells just underneath the epidermis.
              1. Transpiration and movement of water within the plant body
              2. Gutation
              3. Movement of food within the plant body

              I. Transpiration - evaporation of water from shoot.

              Movement of water and minerals in the xylem is a major process. For example, corn plants transpires almost 500 liters of water during its 4 month growing period.

              Water moves in tracheids and vessel members. Tracheids pass water laterally through simple and bordered pits. Vessel elements have an greater diameter and are stacked end to end, so water can flow for longer distances (a centimeter to a meter) before having to transverse a pit.

              II. Gutation results from root pressure (solutes moving into xylem cause water to also move into the xylem from surrounding root cells) when transpiration is negligible. Wet soils at night.

              Factors Affecting Transpiration

              Wind, Internal concentration of carbon dioxide (low concentrations in leaf cause the stomata to open), wind, air temperature, soil, and light intensity. (Light tends to cause stomata to open in the morning and close in the afternoon).

              III. Movement of food within the plant body - transporting organic solutes

              Transport occurs in the sieve-tube members of phloem. Very delicate and easily damaged. This fact has limited a lot of work done on phloem, since it releases callose (glucose polymer) and P-protein (proteinaceous slime) which clog up the sieve-tube plates (perforated).

              Process is initiated by active transport of sugars from the leaf cells to sieve-tube. SOURCE (leaves in summer and fall, roots in the early spring) AND SINKS (buds in the spring fruits, seeds, and roots in the summer and fall) AND THE BULK MOVEMENT OF WATER AND SOLUTES.

              
              

              Corn Roots

              Corn plants are unusual in that they have two distinct sets of roots: regular roots, called seminal roots and nodal roots, which are above the seminal roots and develop from the plant nodes.

              • The seminal root system includes the plant's radicle (the first root emerging from the seed). These roots are responsible for taking up water and nutrients, and for anchoring the plant.
              • The second root system, the nodal roots, is formed about an inch or so below the soil surface, but above the seminal roots. The nodal roots are formed at the base of the coleoptile, which is the primary stem that emerges from the ground. The nodal roots are visible by the V2 stage of development. The seminal roots are important to the survival of the seedling, and damage can delay emergence and stunt development. This is because the corn plant depends on the nutrients present in the seed until the nodal roots are developed. As soon as the coleoptile emerges from the soil, the seminal roots cease to grow.

              Nodal roots that form above the ground are called brace roots, but they function similarly to the nodal roots below the ground. Sometimes brace roots actually penetrate the soil and take up water and nutrients. These roots may be needed for water uptake in some cases, as the crown of a young corn plant is only about 3/4" below the soil surface! Therefore, corn can be vulnerable to dry soil conditions as they don't have a deep root system.

              
              

              2) The Region of Cell Division (Meristematic Region)

              It is located a few millimeters above the root cap. The cells of the meristematic region are typically small, thin-walled, and contain dense protoplasm. Meristematic cells contain three layers: i) Dermatogen – the outermost layer, ii) Plerome – the middle layer, and iii) Periblem – the innermost layer.

              • Performing cell division to produce new cells for the developing root
              • Helping in root elongation
              
              

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