Introductory Plant Biology

Introductory Plant Biology
Art/Science/Knowledge of Plant Biology Introductory Plant Biology Introduction to the major divisions of plant kingdom: Bryophytes (1) Textbook: Chapter 20, pp Lecture 5 Kris Pruski

小配子囊雄配子体

融合生殖,配子配合

Plant Life Cycle – Alternation of Generations
孢子体 sporophyte ：在植物世代交替地生活史中,产生孢子和具2倍数染色体的植物体。由受精卵（合子）发育而来。孢子体世代 sporophyte generation：植物从受精之后开始至减数分裂之前的阶段。配子体 gametophyte ：在植物世代交替的生活史中，产生配子和具单倍数染色体的植物体。配子体世代 gametophyte generation：植物从减数分裂开始至受精之前的阶段

Art/Science/Knowledge
BRYOPHYTES （苔藓植物） Art/Science/Knowledge of Plant Biology Learning objectives: Features distinguishing the Plant Kingdom from other Kingdoms How Bryophytes differ from other plants Differences between thalloid叶状的 and “leafy” 多叶的liverworts 地钱and how a liverwort thallus is distinguished from that of hornwort Life cycle of mosses 苔藓的生活史 Uses of Bryophytes by humans Common features of liverworts, hornworts and mosses

of Plant Biology BRYOPHYTES Introduction to Bryophytes WW I – Sphagnum Moss (bog/peat moss) 泥炭藓, antiseptic(防腐的) properties; now used as soil conditioner Sphagnum moss is one of species of Bryophytes Various habitats (eg. antlers) Can withstand long periods of drought Often micorrhizal fungi (菌根菌)associated with their rhizoids Mosses, liverworts, hornworts 藓\苔\角苔 Mosses ecologically important in transforming wetlands to drylands No phloem or xylem in Bryophytes Most mosses have water conducting cells - hydroids 传水细胞

of Plant Biology BRYOPHYTES Introduction to Bryophytes External water essential for reproduction 繁殖需要水

of Plant Biology BRYOPHYTES Introduction to Bryophytes Hydroids传水细胞 are inefficient and mosses absorb water via whole surface of the plant Most bryophytes are soft (no phloem or xylem) Alternation of Generations 世代交替is typical for bryophytes; in mosses the “leafy” plant is a major part of the gametophyte配子体 generation (produces gametes), while the sporophyte 孢子体 generation (growing from a “leafy” gametophyte) produces the spores孢子 gametophyte generation 配子体世代 sporophyte generation孢子体世代

of Plant Biology BRYOPHYTES All Bryophytes have similar life cycles, chromosomes and habitats Based on their structure they are separated into three different phyla: LIVERWORTS – phylum HEPATICOPHYTA 苔门 HORNWORTS – phylum ANTHOCEROPHYTA 角苔门 MOSSES – phylum BRYOPHYTA 藓门

of Plant Biology BRYOPHYTES LIVERWORTS – phylum HEPATICOPHYTA HORNWORTS – phylum ANTHOCEROPHYTA MOSSES – phylum BRYOPHYTA

BRYOPHYTES- 1. LIVERWORTS
Art/Science/Knowledge of Plant Biology BRYOPHYTES- 1. LIVERWORTS LIVERWORTS – phylum HEPATICOPHYTA Wort (herb) – medieval(中世纪) medicine meaning of liverwort to cure liver diseases Structure and form: about 8000 species; most common are thalloid liverworts (thalli structures leafy-like flat) – 20% species; “leafy” liverworts – 80% species Liverworts differ from mosses and are less complex

BRYOPHYTES- 1. LIVERWORTS
Art/Science/Knowledge of Plant Biology BRYOPHYTES- 1. LIVERWORTS LIVERWORTS – phylum HEPATICOPHYTA 苔门

BRYOPHYTES – 1. LIVERWORTS
Art/Science/Knowledge of Plant Biology BRYOPHYTES – 1. LIVERWORTS Thalloid liverworts – the best known genus is Marchantia 地钱属often found on damp soil after fire - Thallus叶状体 : 30 cells thick/center, 10 cells thick at margins; forks as grows dichotomously(叉状); upper surface is divided into segments each having a small pore opening into interior

Art/Science/Knowledge of Plant Biology BRYOPHYTES – 1. LIVERWORTS Marchantia polymorpha地钱

Art/Science/Knowledge of Plant Biology BRYOPHYTES – 1. LIVERWORTS Thallus叶状体鳞片假根

Art/Science/Knowledge of Plant Biology BRYOPHYTES – 1. LIVERWORTS Thalloid liverworts 1. Marchantia asexual reproduction无性生殖 by gemmae胞芽; tiny, lens-shaped(透似的) pieces of tissue that become detached from the thallus. water necessary!

Gemmae cup胞芽杯

Art/Science/Knowledge of Plant Biology BRYOPHYTES – 1. LIVERWORTS Thalloid liverworts 叶状苔 Marchantia sexual reproduction有性生殖 Sexual reproduction involves: sperm from the male plant fertilizing ova卵 from the female plants. A fertilized ovum卵develops into a small sporophyte孢子体 plant which remains attached to the larger gametophyte 配子体plant. The sporophyte produces male and female spores which develop into free-living gametophyte plants.

Female gametophore 雌生殖器托（颈卵器托） Male gametophore 雄生殖器托（精子器托）

Antheridium containing sperms
Male gametophore (artheridiophore)

Female gametophore (archegoniophore)
地钱的颈卵器托 Female gametophore (archegoniophore) Archegonium containing an egg

基足蒴柄蒴帽孢子母细胞孢子囊孢子体寄生在配子体上 II III I 雌配子体雄配子体

Art/Science/Knowledge of Plant Biology BRYOPHYTES – 1. LIVERWORTS “Leafy” liverworts 叶苔 Abundant in tropical forests and fog belts

Art/Science/Knowledge of Plant Biology BRYOPHYTES – 1. LIVERWORTS “Leafy” liverworts 叶苔 Always have two rows of partially overlapping “leaves” containing oil bodies油体 Leaves have no midribs中脉, often having folds and lobes acting as little water pockets A few rhizoids假根 coming from a third row of under-leaves anchor the plant Life cycle similar to thalloid liverworts

BRYOPHYTES – 2. HORNWORTS
Art/Science/Knowledge of Plant Biology BRYOPHYTES – 2. HORNWORTS HORNWORTS – phylum ANTHOCEROPHYTA 角苔门孢子体配子体

Art/Science/Knowledge of Plant Biology BRYOPHYTES – 2. HORNWORTS 2. HORNWORTS – phylum ANTHOCEROPHYTA Only 100 species world wide Differ from liverworts and mosses – have usually only one large chloroplast in cell, more like algae Often nitrogen-fixing cyanobacteria（固氮菌）grow in hornworts Rhizoids anchor plants

Art/Science/Knowledge of Plant Biology BRYOPHYTES – 2. HORNWORTS HORNWORTS – phylum ANTHOCEROPHYTA Asexual reproduction – by fragmentation or as lobes separate from the main part of thallus; sometimes produce tiny tubers Sexual reproduction –archegonia 颈卵器 and antheridia 精子器are produced in rows beneath surfaces of gametophytes; sporophytes have many stomata; as growth progresses, sporocytes 孢子母细胞 in sporophytes 孢子体 undergo meiosis producing spores

Art/Science/Knowledge of Plant Biology BRYOPHYTES – 2. HORNWORTS

of Plant Biology BRYOPHYTES – 3. MOSSES 3. MOSSES - Phylum Bryophyta 藓纲 About species Three different classes: Peat mosses泥炭藓 True mosses真藓 Rock mosses 岩藓 “Leaves” of moss gametophytes have no mesophyll tissue, stomata, or veins; the blades are one cell thick, except for the midrib and are never lobed or divided, nor have petiols. Water is absorbed directly through the plant surface

of Plant Biology BRYOPHYTES – 3. MOSSES 3. MOSSES - Phylum Bryophyta

of Plant Biology BRYOPHYTES – 3. MOSSES 1. Sexual Reproduction in mosses Both male and female gametangia （配子囊） are produced on the same plant generally Formation of multicellular gametangia often on separate branches （同株异枝） A single egg cell is produced in a cavity in the base of archegonium 颈卵器 Male gametangia, antheridia精子器 are born on short stalks – a mass tissue inside develops into numerous SPERM cells

of Plant Biology BRYOPHYTES – 3. MOSSES 1. Sexual Reproduction in mosses archegonium 颈卵器 antheridium 精子器 Rhizoid gametophyte

of Plant Biology BRYOPHYTES – 3. MOSSES Sexual Reproduction in mosses (cont’d) This mass of sperms is forced out of the top of the antheridium when it absorbs water. Rain is absolutely necessary After release, the sperm mass breaks up into individual cells, each with a pair of flagella. A sperm after swimming down through the archegonium neck, unites with egg forming 2n zygote. Zygote Embryo Sporophyte

III. 蒴盖孢蒴齿藓帽蒴柄 I. II.

of Plant Biology BRYOPHYTES – 3. MOSSES Sexual Reproduction in mosses (cont’d) II. I. III. Sporophyte 孢子体

The Moss Lifecycle 1 Referring to the diagram, the lifecycle of a typical moss can be explained by starting with the spores released from the moss capsule. If the spore falls on to suitable ground, it starts to grow and develops into a small green shoot called a protonema 原丝体. This protonema soon grows buds that become the familiar leafy green stems of a moss. This phase of the moss lifecycle is termed the gametophyte. Art/Science/Knowledge of Plant Biology I.

The Moss Lifecycle 2 -Within some leaves of the gametophyte, special structures develop into male and female sex organs. -The male part is called an antheridium 精子器 and the female part the archegonium 颈卵器 -Inside the antheridium, sperm are produced. They possess tails allowing to swim, in a film of water, to the archegonium. - They are attracted to the archegonium by chemicals released into water. - Once reaching the archegonium they swim down its neck to reach and fertilize the egg within. Art/Science/Knowledge of Plant Biology I. II.

The Moss Lifecycle 3 - The now fertilized egg develops into a structure called the sporophyte. The sporophyte consists of a stem/seta 蒴柄 and a capsule 孢蒴lots of spores are produced. - During the growth period when the seta is elongating and the spores growing and maturing, the capsule is protected by a thin covering called the calyptra 蒴帽. - When the spores are nearly ripe, the calypra 蒴帽falls off revealing a cap that keeps the spores from being released. - Finally, when the spores reach maturity , the cap falls off and, usually in dry weather, the spores are shaken out of the capsule and dispersed by the wind. Art/Science/Knowledge of Plant Biology II. III.

of Plant Biology I. II. III.

of Plant Biology BRYOPHYTES - 3. MOSSES Alternation of generation in mosses: Every plant completes its life cycle passing through two generations, the gametophytic generation and sporophytic generation. These two generations may be independent or gametophytic generation may be independent and sporophytic generation depends on it.

of Plant Biology BRYOPHYTES - 3. MOSSES Alternation of generation in mosses: The gametophyte is haploid in nature and reproduces sexually. It produces male and female sex organs called antheridia 精子器 and archegonia 颈卵器. These sex organs produce male and female haploid gametes by mitosis, which undergoes fusion to start the saprophyte (sporophyte) . Thus, saprophyte (sporophyte) becomes diploid in nature and reproduces asexually by spores.

of Plant Biology BRYOPHYTES - 3. MOSSES Alternation of generation in mosses: Spores are produced after meiosis and are haploid in nature. They germinate to form the gametophyte. In this manner, the two generations alternate with each other. Moss plant is an independent gametophyte, which alternates with dependent saprophyte (sporophyte). It exhibits a true alternation of generation 世代交替.

of Plant Biology BRYOPHYTES - 3. MOSSES

of Plant Biology BRYOPHYTES - Summary Bryophytes (liverworts, hornworts, mosses) occur in varied and also very specific habitats Water is essential for their reproduction; water is absorbed directly through the plant surfaces Liverwort gametophytes with forking thalli are most common but 80% wort species are “leafy”. Marchantia reproduces asexually via gemmae produced in surface cups and via thallus fragments Marchantia reproduces sexually via eggs and sperms produced in archegonia and antheridia

of Plant Biology BRYOPHYTES - Summary Zygote develops into sporophyte. Sporocytes in the capsule undergo meiosis, producing spores. “Leafy” liverworts have two rows of overlapping “leaves” + a third row “underleaves”. Hornworts have one chloroplast in each cell. Their sporophytes are hornlike and have a meristem above the foot. Asexual reproduction of hornworts is by fragmentation; sexual reproduction involves archegonia and antheridia

of Plant Biology BRYOPHYTES - Summary A moss gametophyte consists of an axis to which “leaves” are attached, with rhizoids at the base; water is absorbed directly through plant surface Archegonia (each has one egg) and antheridia (with sperms) are produced at tips of “leafy” shoots. After fertilization, the zygote grows into embryo which is attached to the gametophyte; the sporophyte developing from the embryo consists of capsule and a seta (stem); sporocytes in the capsule undergo meiosis and produce spores, that are later released at the tip of the capsule.

of Plant Biology BRYOPHYTES - Summary 13. When moss spores germinate, protonemata with “leafy” buds develop and then the buds grow into new gametophytes. 14. Mosses and lichens (alga/fungus) are pioneers on bare rocks. Mosses are not edible. Some mosses are used as packing materials. 15. The main use of peat-moss is for soil conditioning. Used commercially.

BRYOPHYTES - Summary Commercial soilless media all containing peat mosses

of Plant Biology BRYOPHYTES - Summary Commercial peat moss mixes

BRYOPHYTES - questions
Art/Science/Knowledge of Plant Biology BRYOPHYTES - questions What features distinguish the bryophytes from other plants? Describe differences between hornwort thallus and of liverwort thailloid Contrast the sporophytes of mosses, liverworts and hornworts What is protonema? Do all bryophytes have them Which parts of life cycle of bryophytes have haploid (n) cells? Which have diploid (2n) cells Why is a bryophyte “leaf” not the same as a flowering plant leaf?

BRYOPHYTES - questions
Art/Science/Knowledge of Plant Biology BRYOPHYTES - questions Define capsule, foot, seta, antheridia, archegonia, thallus and underleaves Which of the bryophyta is the most important for humans? Why? Very few fossils of bryophyta have been found. What are the reasons? Do the multicellular sex structures of plants give them advantages over other organisms with unicellular sex structures? Can you suggest some other possible uses of peat mosses?

of Plant Biology BRYOPHYTES Questions ?

Introductory Plant Biology

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