Transcript Introduction to Plants

Introduction to Plants
CHAPTER 13
PAGES 267-294
Introduction
 Most of the plants you are familiar with produce
flowers.
 Recall not every plant produces flowers, some have
seeds or cone, others have neither.
What are Plants?
 Plants are multicellular eukaryotes with cell walls
made of cellulose.
 Plant cells also have chloroplasts.
 Plants have specialized reproductive organs.
 Male and Female reproductive organs may be found
on the same plant or on different plants.
How do plants obtain food?
 Almost all plants make food by photosynthesis.
 About 1% of plants are consumers: ex Venus Flytrap
 The Venus Flytrap plant, unlike most plants, actively
seeks insects, not to pollinate, but to feed on! You see,
Venus Flytrap plants grow in soils that are poor in
nutrients. And Venus Flytraps catch insects and digest
them for the nutrients that they cannot get from soil.
Venus Flytrap plants do not eat meat. (Don’t feed them
hamburger!)
 Venus Flytrap plants catch and digest insects. Venus
Flytrap plants even catch and digest small frogs.
 Each trap is only good for 4 to 6 catches. After that, the
trap withers, turns brown, and falls off.
What do plants need?
 Plants need temperatures above freezing while they
are actively growing and photosynthesizing.
 They need sunlight, carbon dioxide, and water for
photosynthesis.
 Plants need oxygen for cellular respiration and
minerals to build proteins and other organic
molecules.
 Most plants need roots to grow down into the soil to
absorb water and nutrients.
The importance of plants.
 Read and highlight this part on page 268.
 Weeds are plants that grow where people do not
want them, such as gardens and lawns.
 When people introduce new plants to an area or
habitat and that plant does not have natural
predators or parasites it called invasive.
 The introduced plants may spread rapidly and drive
out the native plants.
Vascular and Non-vascular plants
 Nonvascular Plants examples: Green Algae, Mosses,
liverworts and hornworts. Called bryophytes.
 Vascular Plants are seed and non-seed plants.
 Seed: Conifers and Flowering plants
 Non Seed: Ferns
Non Vascular Plants
 Mosses are non-vascular plants that do not have
flowers or seeds.
 These simple plants typically grow in damp areas
such as forests or wetlands.
 You may have seen large patches of moss growing on
a tree or rock or even on the forest floor.
 While we may think of mosses as small, forgettable
plants, they actually serve several vital roles.
 For example, peat moss can be used as a fuel, carbon
sink, and habitat for many unique organisms.
 You may also see moss used in flower arrangements
or hanging flower baskets.
 Mosses are also useful to many ecosystems because
they can survive in very high or low temperatures
and can even help make soil.
 As for the life cycle of these plants, mosses are
unique because they spend most of their lives with
only one set of genetic material rather than the
normal two sets.
 This would be like living the majority of your life
cycle with only half of your genetic information.
 Unlike more advanced plants, mosses have a
dominant haploid stage.
 Moss gametophytes are generally either male or
female.
 Male gametophytes contain antheridia, which
produce and release the male gamete - sperm.
 Female gametophytes contain archegonia, which
produce the female gamete – eggs..
 This newly formed diploid sporophyte will grow
within the archegonia, eventually developing a foot
that attaches to the gametophyte, a stalk, and a
capsule that contains sporangium.
 Sporocytes within the sporangium undergo
meiosis in order to create spores that are released to
continue this alternation of generations.
 http://education-portal.com/academy/lesson/amoss-life-cycle-dominant-gametophyte.html#lesson
 5:12
Seedless Vascular Plants
 Ferns are able to reproduce without using seeds.
 Ferns are seedless vascular plants.
 Ferns were the first type of vascular plant and are
generally considered to be simpler than vascular
plants that make seeds.
 http://education-portal.com/academy/lesson/afern-life-cycle-plant-reproduction-without-flowersor-seeds.html#lesson
 6:08
Introduction To Gymnosperms
 Gymnosperms are vascular plants that produce
seeds but not flowers.
 These plants are more advanced than ferns but not
quite as complicated as flowering plants.
 Common examples of gymnosperms include ginkgos
and pine trees.
 These all produce seeds but do not make flowers.
 http://education-portal.com/academy/lesson/a-
gymnosperm-life-cycle-reproduction-of-plants-withnaked-seeds.html#lesson
 6:00
Flowering Vascular plants
 Angiosperms (flowering plants) have two
alternative life cycles because they
undergo sexual and asexual reproduction.
 Asexual reproduction creates a clone of the original
plant.
 The advantage to asexual reproduction is that an
individual plant can propagate the species.
 Sexual reproduction creates genetic diversity.
 The seeds produced by sexual reproduction can also
help distribute plants to far away areas.
 Thus, there are two advantages to sexual
reproduction. The next slide Figure 1 shows the
angiosperm life cycle.
Meristems
 The growing tip of a plant is called the meristem.
 You can see this at the tip of a branch, and it is where
new leaves form.
 Angiosperms shift between a vegetative growth
phase (no flowers) and a reproductive growth
phase (flowers).
Diploid vs. Haploid
 Like most other higher organisms, plants
are diploid. This means that they have two copies of
each gene in their nucleus.
 Once copy comes from each parent, which is how we
get genetic diversity.
 Each parent is genetically different, thus the
combination of their genetic material (DNA) creates
a new variation.
 Sperm and egg cells (gametes or gametophytes)
are haploid.
 This means that they have half of the genetic
material of a diploid cell.
 Sexual reproduction requires that the diploid
organism halves its DNA.
 If it did not, then the offspring would inherit all of
each parent's genetic material.
 They would have twice as much DNA as necessary.
 So, developing gametes undergo two stages of cell
division, mitosis (cell division with DNA
replication) and meiosis (cell division without DNA
replication).
 The resulting mature gamete is haploid.
The Angiosperm Sexual Reproduction
Organ: The Flower
 When you look at a flowering plant, the part you can
see is called a sporophyte.
 The flower contains the male and/or female
gametophytes.
 Flowers are actually modified leaves.
 Each flower contains four different types of modified
leaves: carpels, petals, stamens, and sepals.
The Female Gametophyte
 The carpel is the female sex organ. Female
gametophytes develop within the carpel.
 The carpel (megametophyte) is comprised of a
stigma, style, ovary, and ovule.
 The megaspores (egg cells or female gametophytes)
reside within the ovule (macrospore).
 An individual macrospore will undergo meiosis twice
to produce four haploid macrospores.
The Male Gametophyte
 Male gametophytes are called microspores.
 They develop within the male sex organ (anther).
 They also undergo two rounds of meiosis to produce
four haploid cells.
 However, all four haploid cells will develop into
pollen grains (microgametophytes).
Fertilization
 Pollen grains are released from the anther and travel
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to the stigma.
Once bound to the stigma, the tube cell forms a
pollen tube which delivers the sperm to the egg.
Only one sperm nucleus fuses with the egg.
An embryo then begins to develop within the ovary.
The ovary becomes a seed. If the angiosperm
develops fruit, then the ovary wall thickens and
creates the edible portion of the fruit.
Germination, Growth, And Asexual
Reproduction
 A seed develops into a seedling upon germination.
 The seedling will develop into a fully mature diploid
organism.
 The adult organism can reproduce sexually, as
described above.
 It can also reproduce asexually.
 This involves sending out a runner (as with
strawberries), which can travel some distance from
the parent plant.
 A seedling develops where the runner makes contact
with the soil.
 The seedling is a clone of the parent since there was
no introduction of DNA from another plant.
 The seedling and runner cells are also diploid.
 Angiosperms (flowering plants) have two alternative
life cycles because they can reproduce sexually or
asexually. Sexual reproduction creates haploid
gametes, which allows for genetic diversity. It also
allows for seed dispersal far from the parent plant.
 Either sexual or asexual reproduction will complete
the life cycle of an angiosperm.
 Summary video: http://educationportal.com/academy/lesson/an-angiosperm-lifecycle-flowering-plant-reproduction.html#lesson
 An Angiosperm Life Cycle: Flowering Plant
Reproduction approx. 6:19
Tropisms: Phototropic, Geotropic and
Thigmotropic Plant Growth
 In plants, the response to a stimulus is known as
a tropism.
 This plant movement toward or away from a
stimulus can come in many forms.
 Like many words in science, tropism comes from a
Greek word. Tropos means 'to turn'.
 Therefore, a tropism is a turn towards or away from
a stimulus.
Phototropism
 Phototropism is generally the tropism that makes the
most sense.
 We know that plants grow towards the sun, so they
can make food through photosynthesis.
 This movement in response to sunlight is called
phototropism.
Geotropism
 Geo many sound familiar because of words such as
'geography' and 'geology.' Geo means earth;
therefore, geotropism is movement towards or
away from the earth.
 Examples of geotropism include the downward
growth of roots and the upward growth of shoots.
 Roots have specialized cells that sense gravity and
therefore have a positive tropism by growing toward
the pull of gravity.
 Opposite of this is the growth of the shoot, which is
the aboveground portion of the plant.
 The shoot exhibits negative geotropism by growing
away from the earth.
 You can see these growth patterns with lateral roots
and branches: lateral roots will curve down, while
lateral branches will curve up.
Thigmatropism
 Thigma means 'touch' and again, tropos means 'to
turn.'
 Therefore, thigmatropism is the movement
towards or away from touch.
 Plants can be affected by touch both positively and
negatively.
 We can also see a response to touch in vines and
other climbing plants.
Seasonal Growth Cycles: Perennial, Annual and
Biennial Plants
 Seasonal growth cycles can be influenced by several
factors, including temperature, amount of water and
amount of daylight.
 Plants regulate their developmental processes
depending on these factors.
 Seasonal growth cycles are determined by where
plants live, how they reproduce and the role they
play in their environments.
 Many common garden plants only grow for one
season and then need to be replanted the next. These
plants are called annuals.
 Biennials are plants whose entire life cycle occurs
within two years. In the first year, these plants are
only vegetative, meaning that they don't produce
reproductive structures.
 Some plants do not die every year or every other
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year.
These are commonly trees and shrubs.
These perennials persist for many growing
seasons.
Perennial plants must have structures that allow
for them to survive through different seasons.
Perennials can be broken into two main categories:
woody and herbaceous.
Classification of Vascular, Nonvascular, Monocot
& Dicot Plants
 http://education-
portal.com/academy/lesson/classification-ofvascular-nonvascular-monocot-dicotplants.html#lesson
 7:39
 Structure of Plant Stems: Vascular and Ground
Tissue
 The shoot system includes the aboveground
structures of plants. That means it includes the
leaves, buds, stems, flowers and fruits of plants.
 The plant stem is best identified as the part of the plant
above ground that provides support for other structures.
 Some of these other structures include leaves and
flowers. Within the stem, there are several types of
tissue.
 The meristem is the tissue of the stem capable of cell
division.
 Plants also need something to protect their inner
structures from outside elements. On the stem, this is
the epidermis, which contains wax-coated cells for
protection.
 Previously, the concept of vascular tissue was
addressed.
 Remember that vascular tissue is the tissue used to
transport water and nutrients throughout a plant.
 It acts like roads and plumbing, moving around
nutrients and water needed by the plant.
 There are two types of vascular tissue:
xylem and phloem.
 Xylem transports water and dissolved minerals,
while phloem transports food.
 Previously it was pointed out that an easy way to
remember which vascular tissue is which is that
'phloem' and 'food' both start with the same sound.
 This may help you remember that phloem moves
food and that the other tissue, xylem, moves water.
Root System
 Roots serve many purposes for plants, including the
storage of food and the intake of water.
 http://education-portal.com/academy/lesson/rootsystem-growth-the-root-cap-primary-roots-lateralroots.html#lesson
 5:05