Chapter 38
Totipotency
any cell that can divide and asexually generate a close of original organism in multicellular organisms associated with meristemic tissue founds in many plants
For 10,000 years, plant breeders have altered the traits of a few hundred angiosperm species by...
artificial selection, transforming them into today's crops
Vegetative Reproduction
asexual reproduction in plants
Ovary
at base of carpel
The first mitotic division of zygote splits the fertilized egg into...
basal cell and terminal cell --> gives rise to most of embryo
Plumule
basic shoot or stem of an embryo plant
Petals
brightly colored and advertise flower to insects and other pollinators
Dioecious
cannot self-fertilize because different individuals have either staminate or carpellate flowers
Engineer Transgene into Chloroplast DNA of Crop
chloroplast DNA in many plant species is inherited strictly from maternal plan --> transgenes in chloroplast cannot be transferred by pollen
Stamen
consists of stalk (filament) and terminal anther male reproductive organs
Inflorescence**
group of flowers tightly clustered together when walls of ovaries thicken --> fuse together and form one fruit
Complete Flowers
have all 4 basic floral organs
Pericarp
thickened wall of fruit
Suspensor
thread of cells functions in transfer of nutrients to embryo from parents and from endosperm elongates --> pushes embryo deeper into nutritive and protective tissues
Megasporangium
tissue within each ovule where development of embryo sac occurs
Stigma
top of style sticky structure captures pollen
Pollination
transfer of pollen from anther to stigma
Scion
twig grafter onto stock
Double Fertilization
union of 2 sperm cells with different nuclei of embryo sac ensures endosperm will develop only in ovules where egg has been fertilized and prevents angiosperms from squandering nutrients
Imbibition
uptake of water due to low water potential of dry seed causes expanding seed to rupture seed coat and trigger metabolic changes in embryo that enable it to resume growth
Vegetative Propagation
vegetative reproduction facilitated or induced by humans
Genetic Engineering of Apomixis into Transgenic Crops
when seed is produced by apomixis --> embryo and endosperm develop without feritlization transfer of trait to transgenic crops would minimize possibility of transgene escape via pollen because plants could be male sterile without compromising seed or fruit production
Ovules
within ovary
Biofuels
would reduce emissions of greenhouse gas CO2
After double fertilization, the triploid nucleus of the ovule's central cell ______, forming ___________. The endosperm becomes multicellular when __________. Cell walls ______, and endosperm ________.
After double fertilization, the triploid nucleus of the ovule's central cell divides, forming a multinucleate "supercell". The endosperm becomes multicellular when cytokinesis partitions cytoplasm between nuclei. Cell walls form, and endosperm becomes solid.
After landing on a receptive stigma, the pollen grain ________________. The nucleus of generative cell divides ______________.
After landing on a receptive stigma, the pollen grain absorbs moisture and germinates, producing a pollen tube that grows between cells of style toward ovary. The nucleus of generative cell divides by mitosis to produce 2 sperm.
As the male gametophyte matures, the generative cell _______________. The microsporangium breaks open and ___________.
As the male gametophye matures, the generative cell passes into the tube cell and the spore wall is completed. The microsporangium breaks open and releases pollen.
As the pollen tube elongates quickly through ______, the generative cell divides to _____________. Pollen tube grows ____________ where it releases ________________.
As the pollen tube elongates quickly through style, the generative cell divides to produce 2 sperm cells which remain inside tube cell. Pollen tube grows through style into ovary where it releases sperm cells near female gametophyte.
Cotyledons begin to form as _______. After cotyledons appear, ___________.
Cotyledons begin to form as bumps on proembryo. After cotyledons appear, the embryo elongates.
The embryo stops and enters _____________. The embryo and its food supply are enclosed by __________.
The embryo stops and enters dormancy until seed germinated. The embryo and its food supply are enclosed by protective seed coat formed by integuments of ovule.
The megasporocyte enlarges and undergoes meiosis to produce _________. Only 1 survives and _____________. The multinucleate mass is divided by membranes into _____________. At the micropylar end, two ______________. At opposite end are ______________. Other two polar nuclei share _____________. Ovule now consists of ________________.
The megasporocyte enlarges and undergoes meiosis to produce 4 haploid megaspores. Only 1 survives and nucleus of surviving divides 3 times and resulting in 1 large cell with 8 haploid nuclei. The multinucleate mass is divided by membranes into a multicellular female gametophyte, the embryo sac. At the micropylar end, two synergids flank the egg cell and help attract and guide pollen tube to embryo sac. At opposite end are 3 antipodal cells of unknown function. Other two polar nuclei share cytoplasm of large central cell of embryo sac. Ovule now consists of embryo sac and 2 surrounding integuments.
Self-Incompatibility
ability of a plant to reject its own pollen and that of closely related individuals --> can't fertilize eggs
Seed dormancy increases chances that...
germination will occur at a time and place most advantageous to seedling
Possibilities that Some Crops Hybridize with Weed Relatives
1. Crop-to-Weed Transgene Escape 2. Genetic Engineering of Apomixis into Transgenic Crops 3. Engineer Transgene into Chloroplast DNA of Crop 4. Genetically Engineer Flowers That Develop Normally But Fail to Open
Self-recognition blocks pollen tube growth by 1 of 2 molecular mechanisms
1. Gametophytic Self-Incompatibility 2. Sporophytic Self-Incompatibility
Four Floral Organs
1. Sepals 2. Petals 3. Stamens 4. Carpels
The embryo of a grass seed is enclose by two sheathes...
1. coleorhiza 2. coleoptile both aid in soil penetration after germination
The most important features unique to angiosperm life cycle are...
3 F's 1. Flowers 2. double Fertilization 3. Fruits
Each microsporocyte forms ___________. Each micospore then undergoes ______ to produce ______________.
Each microsporocyte forms 4 haploid microspores by meiosis. Each micospore then undergoes mitosis to produce a male gametophyte consisting of only 2 cells: the generative cell and the tube cell.
__________ development precedes embryo development
Endosperm
In response to chemical attractants produced by synergids, the tip of pollen tube___________. Arrival initiates death of _____________, providing ____________. One sperm fertilizes egg to form _____, other sperm combines with _________ to form _________________.
In response to chemical attractants produced by synergids, the tip of pollen tube grows toward micropyle. Arrival initiates death of 1 of 2 synergids, providing pathway into embryo sac for 2 sperm. One sperm fertilizes egg to form zygote, other sperm combines with 2 polar nuclei to form triploid (3n) nucleus in central cell of female gamtophye.
Life cycles of angiosperms and other plants are characterized by ___________, in which haploid (n) and diploid (2n) generations ____________. Diploid plant produces ____________.
Life cycles of angiosperms and other plants are characterized by an alternation of generations, in which haploid (n) and diploid (2n) generations take turns producing each other. Diploid plant produces haploid genes by meiosis.
Most angiosperms interact with insects or other animals that transfer __________. Many species of flowering plants have _____________.
Most angiosperms interact with insects or other animals that transfer pollen directly between flowers. Many species of flowering plants have co-evolved with specific pollinators.
Gametophytic Self-Incompatibility
S-allele in pollen genome governs blocking of fertilization
Sex is not the only way flowering plants ____________. Many species can also reproduce _________________.
Sex is not the only way flowering plants reproduce. Many species can also reproduce asexually, creating offspring that are genetically identical to them.
Two integuments surround each _____________ except at gap called ______.
Two integuments surround each megasporangium except at gap called micropyle.
When reproducing asexually, a plant passes on _________ to its offspring. When reproducing sexually, it passes on ___________.
When reproducing asexually, a plant passes on all of its genes to its offspring. When reproducing sexually, it passes on only half of its genes.
The terminal cell divides several times and forms...
a spherical proembryo attached to suspensor
Anther
contains chambers called microsporangia (pollen sacs) that produce pollen
Coleorhiza
covers young root
Coleoptil
covers young shoot
Multiple Fruit
develops from inflorescence
Apomixis
different method of asexual reproduction produce seeds without flowers being fertilized --> diploid cell in ovules gives rise to embryo and ovules mature into seeds
Within the microsporangia are many...
diploid cells call microsporocytes or microspore mother cells
Basal cell continues to...
divide to produce thread of cells (suspensor) which anchors embryo to parent
Sporophyte
dominant generation --> large, conspicuous, long-lived plant we see
Hypocotyl
embryonic axis terminates radicle
Radicle
embryonic root
Sepals
enclose and protect floral bud before it opens usually green and more leaflike in appearance than other floral organs
The cotyledons absorb nutrients from...
endosperm and transfer them to embryo when seed germinates
The various barriers that prevent self-fertilization contribute to genetic variety by...
ensuring that sperm and egg come from different parents
Embryo Sac
female gametophyte
Sporophytic Self-Incompatibility
fertilization blocked by S-allele gene products in tissues of parental sporophyte that adhere to pollen wall
Polyspermy
fertilization of egg by more than 1 sperm cell
Inflorescenes
flowers arranged in tight and showy clusters
Endosperm
food storing tissue of seed
Simple Fruits
fruits derived from single carpel or several fused carpels
Advantages of Sexual Reproduction
generates variation in offspring seeds produced can disperse to new locations and wait for favorable growing conditions
S-Genes
genes for self-incompatibility governs blocking of fertilization
Transgenic
genetically modified plants that have been genetically engineered to express gene from another species
Disadvantage of Asexual Reproduction
genotypic uniformity puts asexually produced plants at great risk of local extinction if there is a catastrophic environmental change i.e. a new strain of disease
Incomplete Flowers
lack sepals, petals, stamens, and carpels either sterile (lacking functional stamens and carpels) or unisexual (lacking stamens or carpels)
Staminate
lacking carpels
Carpellate
lacking stamens
Integuments
layers of protective sporophytic tissue that eventually develops into seed coat
Crop-To-Weed Transgene Escape
likelihood depends on ability of crop and weed to hyrbidize and on how transgenes affect overall fitness of hybrids
Pollen Tube
long cellular protuberance that delivers sperm to female gametophyte
Pollen Grain
made up of generative cell, tube cell, and spore wall
Callus
mass of dividing, undifferentiated cells forms where stem is cut and produces adventitious roots
Megasporocyte
megaspore mother cell
Advantages of Asexual Reproduction
no need for pollinator --> beneficial if plants of same species are sparsely distributes and unlikely to be visited by same pollinator plant can clone many copies of itself rapidly --> clones can be well suited to environment
Asexual Reproduction
offspring derived from a single parent without genetic recombination extension of capacity of plants for indeterminate growth
Accessory Fruits
other floral parts in angiosperm contribute to fruit
Ovule After Double Fertilization
ovule develops into seed and ovary develops into fruit enclosing seed
Fragmentation
parent plant separates into parts that re-form into whole plants
Protoplast Fusion
plant cells that have had cell walls removed enzymatically by fungal cellulases and pectinases
Stock
plant that provides root system
Epicotyl
portion of embryonic axis above where cotyledons are attached and below first pair of miniature leaves
Selfing
process sexual reproduction increases genetic diversity of offspring
Spore Wall
produced by microspore and anther has a unique pattern characteristic of species
Fruit
protects enclosed seeds and aids in dispersal by wind or animals
The first organ to emerge from germinating seed is...
radicle --> embryonic root stabilizes plant
Pistil
refers to a single carpel or two or more fused carpels
Stamen and carpels are _________ where sepals and petals are _________
reproductive organs sterile
Aggregate Fruit
results from single flower that has more than 1 carpel --> each forms small fruit fruitlets clustered together on single receptacle
Fertilization
results in diploid zygotes which divide by mitosis to form new sporophytes
Genetically Engineer Flowers That Develop Normally But Fail to Open
self-pollination would occur but pollen wouldn't escape flower
Receptacle
site of attachment to stem
Style
slender neck of carpel
The modification of plants has increased dramatically with...
the advent of genetic engineering
