Anatomy in relation to taxonomy by venkat parker venkatparker
This document discusses the importance of anatomical features in plant taxonomy and systematics. It provides examples of how wood anatomy, trichomes, epidermal features, leaf anatomy, floral anatomy, and plastid types have helped elucidate phylogenetic relationships. Wood anatomy separates Paeonia and Austrobaileya into distinct families. Nodal anatomy and stomatal types also distinguish plant groups. Leaf anatomy helped develop the gonophyll theory and reject fossil plants. Floral anatomy supports separating Menyanthes and Gentianaceae. Plastid types separate Aizoaceae and Molluginaceae.
This document provides information about the fern genus Osmunda. It discusses the systematic position and distribution of Osmunda species. It describes the sporophyte structures including roots, stems, leaves, and internal anatomy. It covers the development and dehiscence of sporangia and gametophytes. Finally, it mentions some economic uses of Osmunda including using roots and rhizomes for fiber and as growing medium for orchids.
The document summarizes the types and positions of sori (clusters of sporangia) in ferns. There are three main types of sori: simplices where all sporangia mature simultaneously; gradatae where sporangia mature basipetally from distal to proximal ends; and mixtae which are a mixed aggregation of young and old sporangia. Sori can be marginal, ventral, or borne within structures like sporocarps. Some sori have an indusium or scale for protection, and these can have reniform, circular, funnel-shaped or other morphologies.
Embyrology in relation to Taxonomy. It is one of the concepts in Modern Taxonomy.in which embryological data is used to strengthen existing classification system.
This document summarizes ultrastructural and nuclear cytology studies in embryos. It discusses how cytology studies cell structure and function, and embryology studies embryonic development. It then describes ultrastructural studies showing how early embryos differentiate into suspensors and embryo proper in many angiosperms. The suspensor diversity and structures like haustoria are discussed. Finally, nuclear cytology studies in the plant species Sedum reflexum are summarized, noting the suspensor consists of a basal and chalazal cells, and the basal cell produces a branched haustorium and has dense cytoplasm rich in organelles.
Anatomy in relation to taxonomy by venkat parker venkatparker
This document discusses the importance of anatomical features in plant taxonomy and systematics. It provides examples of how wood anatomy, trichomes, epidermal features, leaf anatomy, floral anatomy, and plastid types have helped elucidate phylogenetic relationships. Wood anatomy separates Paeonia and Austrobaileya into distinct families. Nodal anatomy and stomatal types also distinguish plant groups. Leaf anatomy helped develop the gonophyll theory and reject fossil plants. Floral anatomy supports separating Menyanthes and Gentianaceae. Plastid types separate Aizoaceae and Molluginaceae.
This document provides information about the fern genus Osmunda. It discusses the systematic position and distribution of Osmunda species. It describes the sporophyte structures including roots, stems, leaves, and internal anatomy. It covers the development and dehiscence of sporangia and gametophytes. Finally, it mentions some economic uses of Osmunda including using roots and rhizomes for fiber and as growing medium for orchids.
The document summarizes the types and positions of sori (clusters of sporangia) in ferns. There are three main types of sori: simplices where all sporangia mature simultaneously; gradatae where sporangia mature basipetally from distal to proximal ends; and mixtae which are a mixed aggregation of young and old sporangia. Sori can be marginal, ventral, or borne within structures like sporocarps. Some sori have an indusium or scale for protection, and these can have reniform, circular, funnel-shaped or other morphologies.
Embyrology in relation to Taxonomy. It is one of the concepts in Modern Taxonomy.in which embryological data is used to strengthen existing classification system.
This document summarizes ultrastructural and nuclear cytology studies in embryos. It discusses how cytology studies cell structure and function, and embryology studies embryonic development. It then describes ultrastructural studies showing how early embryos differentiate into suspensors and embryo proper in many angiosperms. The suspensor diversity and structures like haustoria are discussed. Finally, nuclear cytology studies in the plant species Sedum reflexum are summarized, noting the suspensor consists of a basal and chalazal cells, and the basal cell produces a branched haustorium and has dense cytoplasm rich in organelles.
CONTROL OF XYLEM AND PHOLEM DIFFERENTIATION .pptxHarshalaNaik3
Plant vascular systems are usually composed of phloem and xylem. Phloem often develops without xylem, whereas xylem does not form without phloem. Low levels of auxin induce phloem differentiation but not xylem, while high auxin induces both. Other factors like gibberellic acid, sugars, leaves, roots, cytokinins, pressure and ethylene also influence phloem and xylem differentiation. The dynamic interplay between these various signals precisely controls vascular development.
This document discusses anomalous secondary growth in plants. It begins by defining anomalous secondary growth as a deviation from normal cambial activity in dicots. There are two types of anomalous growth: adaptive and non-adaptive. Adaptive growth includes woody climbers, while non-adaptive includes plants like Rumex and Chenopodium.
The document then describes two types of anomalous secondary growth: 1) abnormal behavior of the normal cambium and 2) abnormal behavior of an abnormal cambium. In type 1, the cambium forms vascular tissue only in bundle regions or produces more vascular tissue in bundles, seen in plants like Cucurbita and Bignonia. In type 2, accessory cambia form rings of vascular bundles
The document discusses two theories on the evolution of the sporophyte in bryophytes:
1) The theory of progressive sterilization proposes that sporophytes evolved through the progressive sterilization of potential sporogenous tissue, with simpler forms like Riccia having a higher proportion of fertile tissue and more complex forms like Funaria having more sterile tissues like feet, setae, and capsule walls.
2) The reduction theory proposes that sporophyte evolution occurred through the downward reduction and simplification of structures, with features like dehiscence apparatuses, photosynthetic capsule walls, and structures like the foot and seta disappearing over time. Supporters believe the simple sporophyte of Riccia represents
This document summarizes the development of the female gametophyte in angiosperms. It begins with an introduction to the megaspore mother cell and its development into the female gametophyte through meiosis. There are three main types of female gametophytes - monosporic, bisporic, and tetrasporic - which are distinguished by the number of megaspores involved. A monosporic gametophyte develops from a single megaspore, while bisporic and tetrasporic involve two and four megaspores, respectively. Examples of each type are provided, including the common Polygonum type of monosporic gametophyte and the Allium and
Microsporogenesis involves the formation of pollen grains in the anthers. It begins with the formation of archesporial cells that develop into primary sporogenous cells. These cells undergo mitosis and differentiate into microspore mother cells. The microspore mother cells undergo meiosis to form microspores still connected in tetrads. The tetrads separate into individual microspores which are released from the anther as mature pollen grains. Key tissues involved include the sporogenous tissue, tapetum, and anther wall layers.
This document discusses apogamy and apospory in plants. It defines apogamy as asexual reproduction in ferns where a haploid gametophyte develops into a haploid sporophyte without gamete fusion. Apospory is defined as the development of a diploid gametophyte from the vegetative cells of a diploid sporophyte, without meiosis or spore formation. The key difference between the two is that apogamy produces a haploid embryo while apospory produces a diploid embryo. Causes of each include environmental stresses that prevent normal sexual reproduction. Similarities include that both are asexual reproductive processes that occur in bryophytes and involve alternation of generations
Sphagnum, or peat moss, is a perennial bryophyte that grows in wet areas, forming dense mats. It has a unique leaf structure of chlorophyll-containing and hyaline cells. The gametophyte reproduces vegetatively through innovations, gemmae, and protonemal branches. Sexual reproduction involves antheridia and archegonia on separate monoecious or dioecious plants. Fertilization results in a sporophyte with a bulbous foot, spherical capsule, and columella containing haploid spores. Germination of spores forms a protonema that develops into a new gametophyte.
1. Selaginella is a heterosporous plant that produces megaspores and microspores. The spores develop into male and female gametophytes within their spore walls.
2. Microspores develop into male gametophytes containing antherozoids for fertilization. Megaspores develop into female gametophytes containing archegonia.
3. Fertilization occurs when antherozoids enter the archegonia through openings in the neck canal cells. This leads to the development of a diploid sporophyte within the megaspore.
The document summarizes microsporogenesis, the development of the male gametophyte, and pollen morphology. It describes the structure of the anther and the development of microspores through meiosis within the microsporangia. The tapetum layer provides nutrients and enzymes that help separate microspores into pollen grains. Pollen grains contain a vegetative cell that divides to form two sperm cells or a generative cell that divides into two sperm, comprising the male germ unit that travels within the pollen tube. Pollen grains have an outer sculpted exine layer and inner intine layer. Their size, symmetry, and exine ornamentation vary between species.
The plant Psilotum is a small shrub that reproduces both sexually and asexually. Its sporophyte body has underground rhizomes and aerial branches. Sporangia form in triads in the axils of leaves and contain spores that develop into subterranean gametophytes. The gametophytes are monoecious and bear both antheridia and archegonia. Fertilization occurs when sperm from the antheridia enter the archegonia. The resulting zygote divides to form an embryo sporophyte surrounded by gametophyte tissue. The sporophyte matures into a new Psilotum plant.
This document summarizes research on somatic embryogenesis in rice. It describes the process of somatic embryogenesis, including the stages of embryogenesis and factors that affect it. The methodology section outlines the materials and methods used, including collecting rice seeds as explants, sterilizing them, and culturing them on callus induction and embryo germination media with different concentrations of plant growth regulators like 2,4-D, BAP and NAA. The goal is to develop an efficient system for somatic embryogenesis and plant regeneration in rice.
Specialized tissue or secretary tissue produce and secrete a variety of substances. There are two main types of secretory tissues: laticiferous tissues and glandular tissues. Laticiferous tissues consist of elongated ducts that contain latex, a milky substance rich in proteins, carbohydrates, and other compounds. Glandular tissues contain glands that secrete oils, resins, enzymes and other substances. Secretions may remain within the cells or be released and have various functions in the plant or commercial value.
The document discusses the development of dicot and monocot embryos. It begins by explaining that the embryo contains the earliest forms of a plant's roots, stem, and leaves and acts as a "starter kit" for the plant. For both dicots and monocots, fertilization results in a zygote that develops into an embryo, though dicot embryos generally have two cotyledons while monocot embryos have one. The document then describes the specific cell divisions and stages - including proembryo, octant, and cotyledon stages - that characterize the development of dicot and monocot embryos.
After double fertilization and triple fusion, the zygote secretes a cellulose wall and divides into two cells - an upper embryonal cell and lower suspensor cell. The embryonal cell divides into eight octant cells which then divide further, forming a surface layer of dermatogen cells and an inner embryonal mass. The dermatogens and embryonal mass cells continue dividing and differentiating to form the various parts of the embryo, including the plumule, cotyledons, radicle, and hypocotyledons.
This document provides information about the order Ginkgoales. It discusses that Ginkgoales is an ancient order of gymnosperms that is now only represented by one surviving species, Ginkgo biloba, known as the living fossil. The document describes the morphological features and life cycle of G. biloba, including its fan-shaped leaves, dioecious reproduction, and development of male microsporangia and female megasporangia. It also notes the economic and medicinal uses of G. biloba as an ornamental shade tree and treatment for memory problems.
The document discusses the root-stem transition zone in plants. It begins by explaining that the root has a radial vascular structure while the stem has a conjoint structure, so there must be a region where these structures merge. This region is called the root-stem transition zone. The document then describes four types of root-stem transitions (Fumaria, Cucurbita, Lathyrus, and Anemarrhena) which differ in how the xylem and phloem structures divide and rearrange as they transition from root to stem. Finally, it notes that the transition zone represents a different internal arrangement than the root or stem and reflects different evolutionary stages in the development of the vascular system.
The "Telome theory" of Walter Zimmermann (1930, 1952) is the most accepted theory that is based on fossil record and synthesizes the major steps in the evolution of vascular plants.
It describes how the primitive type of vascular plants developed from Rhynia like plants.
The document discusses periderm, the protective layer of bark that forms in plants. It is composed of three layers: the phellogen or cork cambium, the phellem or cork layer, and the phelloderm. The document describes where the phellogen layer originates in different plant species, either just under the epidermis or deeper in the stem tissue. It also discusses lenticels, which allow gas exchange, and rhytidome, the layers of old periderm. Commercial cork is harvested from cork oak trees.
Secondary growth occurs in woody stems and roots through the activity of vascular cambium, which adds secondary xylem inward and secondary phloem outward. This increases the girth of the plant. In temperate regions, tree rings form from differences between early and late secondary xylem, and can be used to estimate a tree's age and study past climate. Cork cambium also forms a protective periderm layer over the stem. Together, secondary growth and protective layers allow woody plants to grow larger.
CONTROL OF XYLEM AND PHOLEM DIFFERENTIATION .pptxHarshalaNaik3
Plant vascular systems are usually composed of phloem and xylem. Phloem often develops without xylem, whereas xylem does not form without phloem. Low levels of auxin induce phloem differentiation but not xylem, while high auxin induces both. Other factors like gibberellic acid, sugars, leaves, roots, cytokinins, pressure and ethylene also influence phloem and xylem differentiation. The dynamic interplay between these various signals precisely controls vascular development.
This document discusses anomalous secondary growth in plants. It begins by defining anomalous secondary growth as a deviation from normal cambial activity in dicots. There are two types of anomalous growth: adaptive and non-adaptive. Adaptive growth includes woody climbers, while non-adaptive includes plants like Rumex and Chenopodium.
The document then describes two types of anomalous secondary growth: 1) abnormal behavior of the normal cambium and 2) abnormal behavior of an abnormal cambium. In type 1, the cambium forms vascular tissue only in bundle regions or produces more vascular tissue in bundles, seen in plants like Cucurbita and Bignonia. In type 2, accessory cambia form rings of vascular bundles
The document discusses two theories on the evolution of the sporophyte in bryophytes:
1) The theory of progressive sterilization proposes that sporophytes evolved through the progressive sterilization of potential sporogenous tissue, with simpler forms like Riccia having a higher proportion of fertile tissue and more complex forms like Funaria having more sterile tissues like feet, setae, and capsule walls.
2) The reduction theory proposes that sporophyte evolution occurred through the downward reduction and simplification of structures, with features like dehiscence apparatuses, photosynthetic capsule walls, and structures like the foot and seta disappearing over time. Supporters believe the simple sporophyte of Riccia represents
This document summarizes the development of the female gametophyte in angiosperms. It begins with an introduction to the megaspore mother cell and its development into the female gametophyte through meiosis. There are three main types of female gametophytes - monosporic, bisporic, and tetrasporic - which are distinguished by the number of megaspores involved. A monosporic gametophyte develops from a single megaspore, while bisporic and tetrasporic involve two and four megaspores, respectively. Examples of each type are provided, including the common Polygonum type of monosporic gametophyte and the Allium and
Microsporogenesis involves the formation of pollen grains in the anthers. It begins with the formation of archesporial cells that develop into primary sporogenous cells. These cells undergo mitosis and differentiate into microspore mother cells. The microspore mother cells undergo meiosis to form microspores still connected in tetrads. The tetrads separate into individual microspores which are released from the anther as mature pollen grains. Key tissues involved include the sporogenous tissue, tapetum, and anther wall layers.
This document discusses apogamy and apospory in plants. It defines apogamy as asexual reproduction in ferns where a haploid gametophyte develops into a haploid sporophyte without gamete fusion. Apospory is defined as the development of a diploid gametophyte from the vegetative cells of a diploid sporophyte, without meiosis or spore formation. The key difference between the two is that apogamy produces a haploid embryo while apospory produces a diploid embryo. Causes of each include environmental stresses that prevent normal sexual reproduction. Similarities include that both are asexual reproductive processes that occur in bryophytes and involve alternation of generations
Sphagnum, or peat moss, is a perennial bryophyte that grows in wet areas, forming dense mats. It has a unique leaf structure of chlorophyll-containing and hyaline cells. The gametophyte reproduces vegetatively through innovations, gemmae, and protonemal branches. Sexual reproduction involves antheridia and archegonia on separate monoecious or dioecious plants. Fertilization results in a sporophyte with a bulbous foot, spherical capsule, and columella containing haploid spores. Germination of spores forms a protonema that develops into a new gametophyte.
1. Selaginella is a heterosporous plant that produces megaspores and microspores. The spores develop into male and female gametophytes within their spore walls.
2. Microspores develop into male gametophytes containing antherozoids for fertilization. Megaspores develop into female gametophytes containing archegonia.
3. Fertilization occurs when antherozoids enter the archegonia through openings in the neck canal cells. This leads to the development of a diploid sporophyte within the megaspore.
The document summarizes microsporogenesis, the development of the male gametophyte, and pollen morphology. It describes the structure of the anther and the development of microspores through meiosis within the microsporangia. The tapetum layer provides nutrients and enzymes that help separate microspores into pollen grains. Pollen grains contain a vegetative cell that divides to form two sperm cells or a generative cell that divides into two sperm, comprising the male germ unit that travels within the pollen tube. Pollen grains have an outer sculpted exine layer and inner intine layer. Their size, symmetry, and exine ornamentation vary between species.
The plant Psilotum is a small shrub that reproduces both sexually and asexually. Its sporophyte body has underground rhizomes and aerial branches. Sporangia form in triads in the axils of leaves and contain spores that develop into subterranean gametophytes. The gametophytes are monoecious and bear both antheridia and archegonia. Fertilization occurs when sperm from the antheridia enter the archegonia. The resulting zygote divides to form an embryo sporophyte surrounded by gametophyte tissue. The sporophyte matures into a new Psilotum plant.
This document summarizes research on somatic embryogenesis in rice. It describes the process of somatic embryogenesis, including the stages of embryogenesis and factors that affect it. The methodology section outlines the materials and methods used, including collecting rice seeds as explants, sterilizing them, and culturing them on callus induction and embryo germination media with different concentrations of plant growth regulators like 2,4-D, BAP and NAA. The goal is to develop an efficient system for somatic embryogenesis and plant regeneration in rice.
Specialized tissue or secretary tissue produce and secrete a variety of substances. There are two main types of secretory tissues: laticiferous tissues and glandular tissues. Laticiferous tissues consist of elongated ducts that contain latex, a milky substance rich in proteins, carbohydrates, and other compounds. Glandular tissues contain glands that secrete oils, resins, enzymes and other substances. Secretions may remain within the cells or be released and have various functions in the plant or commercial value.
The document discusses the development of dicot and monocot embryos. It begins by explaining that the embryo contains the earliest forms of a plant's roots, stem, and leaves and acts as a "starter kit" for the plant. For both dicots and monocots, fertilization results in a zygote that develops into an embryo, though dicot embryos generally have two cotyledons while monocot embryos have one. The document then describes the specific cell divisions and stages - including proembryo, octant, and cotyledon stages - that characterize the development of dicot and monocot embryos.
After double fertilization and triple fusion, the zygote secretes a cellulose wall and divides into two cells - an upper embryonal cell and lower suspensor cell. The embryonal cell divides into eight octant cells which then divide further, forming a surface layer of dermatogen cells and an inner embryonal mass. The dermatogens and embryonal mass cells continue dividing and differentiating to form the various parts of the embryo, including the plumule, cotyledons, radicle, and hypocotyledons.
This document provides information about the order Ginkgoales. It discusses that Ginkgoales is an ancient order of gymnosperms that is now only represented by one surviving species, Ginkgo biloba, known as the living fossil. The document describes the morphological features and life cycle of G. biloba, including its fan-shaped leaves, dioecious reproduction, and development of male microsporangia and female megasporangia. It also notes the economic and medicinal uses of G. biloba as an ornamental shade tree and treatment for memory problems.
The document discusses the root-stem transition zone in plants. It begins by explaining that the root has a radial vascular structure while the stem has a conjoint structure, so there must be a region where these structures merge. This region is called the root-stem transition zone. The document then describes four types of root-stem transitions (Fumaria, Cucurbita, Lathyrus, and Anemarrhena) which differ in how the xylem and phloem structures divide and rearrange as they transition from root to stem. Finally, it notes that the transition zone represents a different internal arrangement than the root or stem and reflects different evolutionary stages in the development of the vascular system.
The "Telome theory" of Walter Zimmermann (1930, 1952) is the most accepted theory that is based on fossil record and synthesizes the major steps in the evolution of vascular plants.
It describes how the primitive type of vascular plants developed from Rhynia like plants.
The document discusses periderm, the protective layer of bark that forms in plants. It is composed of three layers: the phellogen or cork cambium, the phellem or cork layer, and the phelloderm. The document describes where the phellogen layer originates in different plant species, either just under the epidermis or deeper in the stem tissue. It also discusses lenticels, which allow gas exchange, and rhytidome, the layers of old periderm. Commercial cork is harvested from cork oak trees.
Secondary growth occurs in woody stems and roots through the activity of vascular cambium, which adds secondary xylem inward and secondary phloem outward. This increases the girth of the plant. In temperate regions, tree rings form from differences between early and late secondary xylem, and can be used to estimate a tree's age and study past climate. Cork cambium also forms a protective periderm layer over the stem. Together, secondary growth and protective layers allow woody plants to grow larger.
Meristems are regions of active cell division that give rise to the different cell types in plants. There are two types of meristems - primary meristems result in growth in length through cell division while secondary meristems result in growth in width. Plants are composed of three main tissue types - dermal tissues which form the outer layers, ground tissues which make up the internal structure, and vascular tissues which transport water and nutrients. These tissues are made up of specialized cell types that carry out functions like protection, photosynthesis, storage, and transport.
This document summarizes research on the diversity of Psathyrella fungi in the Punjab region of India. Three new Psathyrella species were discovered during surveys of various habitats across four districts. The species were systematically analyzed using microscopic characteristics and compared to known taxa. Overall the study found diversity within the genus Psathyrella in Punjab and identified three new species, contributing to the knowledge of agaric fungi in the region.
Three new species of the genus Agaricus were discovered in Punjab, India between 2008-2012: A. stellatus-cuticus, A. punjabensis, and A. patialensis. A. stellatus-cuticus is characterized by a stellate splitting cap surface and abundant cheilocystidia. A. punjabensis is campestroid with an annulate stipe lacking brown scales and a pileus cuticle that does not change in KOH. A. patialensis has small, golden brown carpophores with a distinctly bulbous stipe. These new discoveries were identified through detailed examination of macroscopic and microscopic characteristics.
This document discusses various methods for germline transformation in plants. It begins with introducing germline transformation as the process of altering an organism's genetic makeup by inserting new DNA into its genome, usually using vectors like plasmids. It then describes several methods for accomplishing plant transformation, including the pollen tube pathway method, Agrobacterium-mediated method, electrofusion, floral dip method, and biolistic method. The document provides details on the history and protocol of the pollen tube pathway method for plant transformation.
1) The document discusses various types of embryogenesis including the Onagrad, Asterad, Solanad, Chenopodiad, and Caryophyllad types.
2) It provides examples of plant families that exhibit each type and describes how the apical and basal cells divide and contribute to embryo formation.
3) General patterns of embryo development are described for dicots using Ceratocephalus falcatus as an example, and for monocots using Najas lacerata.
The vascular cambium is a lateral meristem that increases the diameter of stems and roots through secondary growth. It is composed of fusiform initials that divide to form vertical tissues and ray initials that form horizontal tissues. In dicots, intrafascicular cambium initially develops within vascular bundles and interfascicular cambium develops between bundles, eventually joining to form a complete cambial ring. The cambium divides to produce secondary xylem internally and secondary phloem externally. Its seasonal activity varies the structure of the tissues produced.
Wall ingrowths are specialized structures that increase the surface area of plant cell membranes. They are formed through localized deposition of cell wall material which causes invaginations of the plasma membrane. There are three main types of wall ingrowths - flange, reticulate, and papillate. Flange ingrowths resemble secondary cell walls while reticulate ingrowths branch and fuse to form fenestrations. Papillate ingrowths are initially disorganized cellulose deposits that become surrounded by callose and cell wall proteins. Transfer cells are specialized plant cells that facilitate nutrient transport through extensive wall ingrowths that amplify the plasma membrane surface area.
Reaction wood forms in trees in response to gravitational stimuli that cause stems or branches to bend or lean. There are two types of reaction wood - tension wood in angiosperms and compression wood in gymnosperms. Tension wood forms on the upper side of leaning branches and stems and has high cellulose content, helping pull the branch upwards. Compression wood forms on the lower side and has high lignin, helping straighten and compress the leaning area. The formation of reaction wood helps maintain the angle of bent or leaning parts of trees through its differing mechanical properties compared to normal wood.
Plasmodesmata are narrow strands of cytoplasm that connect adjacent plant cells and allow for transport of substances between cells. They were first observed under light microscopes in 1879 but required electron microscopes to confirm their nature as cytoplasmic strands. Plasmodesmata contain a plasma membrane-lined channel and a desmotubule made of tightly constricted endoplasmic reticulum. Substances move between cells through the region between the desmotubule and plasma membrane, called the cytoplasmic sleeve. Plasmodesmata are either primary, formed during cell division, or secondary, formed across existing cell walls.
The document discusses different types of secretory tissues in plants, specifically laticifers. Laticifers are specialized parenchyma cells that transport latex, a suspension containing various substances like resins, proteins, oils, alkaloids and sugars. Laticifers can be non-articulate or articulate. Non-articulate laticifers are long multinucleated cells that branch extensively through tissues. Articulate laticifers form longitudinal chains of cells joined end to end, resembling xylem vessels. Articulate laticifers can be non-anastomosing or anastomosing, where the latter form net-like reticula through lateral connections. Specific plant families and examples of
#1. Xerophytes and hydrophytes have anatomical adaptations to reduce water loss and absorb water efficiently.
#2. Xerophytes develop thick cuticles, sunken stomata, hair coverage, rolling leaves, reduced leaf surface area, and water storage tissues.
#3. Hydrophytes have thin cuticles, air chambers for gas exchange and buoyancy, and absorb water through their entire surfaces.
Dendrochronology is the study of tree rings to determine a tree's age and learn about past climate conditions. It works by matching patterns of wide and narrow tree rings between core samples from the same tree and across different trees. This technique, called crossdating, allows scientists to assign exact years to each tree ring. Dendrochronology reveals that tree growth and ring patterns correlate with climate - trees grow better rings in warm, wet conditions and poorer rings when cold and dry. Only trees in temperate zones exhibit clear annual growth rings due to seasonal climate changes.
Lenticels are raised spots on tree bark through which gas exchange occurs. They form under stomata and their number depends on stomata. Lenticels develop as parenchyma cells near stomata divide irregularly, forming loose colorless cells called complementary cells. Complementary cells increase in number, pushing against the epidermis and causing it to rupture. There are three types of lenticels distinguished by their filling tissue composition and structure. Lenticels allow for gas exchange at night or when stomata are closed and permit a small amount of transpiration.
Structural and biochemical defense mechanisms help plants defend against pathogens. Structural defenses include pre-existing structures like cuticular wax, thick cuticles, and tough cell walls, as well as structures that develop after infection, such as cell wall thickening, callose deposition, and formation of layers and cork. Biochemical defenses include pre-existing inhibitors that prevent pathogen germination and growth, as well as responses after infection like phytoalexin production, oxidative burst, and hypersensitive response cell death. These multifaceted defense strategies help plants resist invading pathogens.