Plant science

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IntroductionIntroduction
to Plantto Plant
ScienceScience

Importance of Plants in our LivesImportance of Plants in our Lives
 Plants provide us with the basis of survivalPlants provide us with the basis of survival
 Wheat and barley are among the oldest knownWheat and barley are among the oldest known
cultivated cropscultivated crops
 Plants can thrive without people and animals; however,Plants can thrive without people and animals; however,
people and animals can NOT survive without plants.people and animals can NOT survive without plants.
 Plant provide us with food, oxygen, fossil fuels,Plant provide us with food, oxygen, fossil fuels,
vaccines, medicines, and prevent the erosion of soil.vaccines, medicines, and prevent the erosion of soil.
 Herbivores consume approximately 10% of the plantHerbivores consume approximately 10% of the plant
biomass produced in a typical food chain.biomass produced in a typical food chain.
 Carnivores capture and consume about 10% of theCarnivores capture and consume about 10% of the
energy stored by the herbivores.energy stored by the herbivores.
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Significance of the BinomialSignificance of the Binomial
System of Naming PlantsSystem of Naming Plants
 There are over 500,000 different recognizedThere are over 500,000 different recognized
plants in the world.plants in the world.
 The Binomial System was developed byThe Binomial System was developed by
Carolus Linnaeus.Carolus Linnaeus.
 The first word is the genusThe first word is the genus
 Second word is the speciesSecond word is the species
 Third word is the authority of abbreviationThird word is the authority of abbreviation
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Example of Plant NamesExample of Plant Names
 Rice –Rice – Oryza sativaOryza sativa
 Onion –Onion – Allium cepaAllium cepa
 Orange –Orange – Citrus sinensisCitrus sinensis
 SunflowerSunflower - Helianthus annuus- Helianthus annuus
 Pineapple -Pineapple - Ananas comosusAnanas comosus
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Example of Animal NamesExample of Animal Names
 Dog –Dog – Canis lupusCanis lupus
 Cat –Cat – Felis catusFelis catus

Introduction to PlantsIntroduction to Plants
 The kingdom PlantaeThe kingdom Plantae
encompasses water-encompasses water-
dwelling red and greendwelling red and green
algae as well asalgae as well as
terrestrial plants, whichterrestrial plants, which
have evolved to supporthave evolved to support
themselves outside ofthemselves outside of
the aquatic environmentthe aquatic environment
of their ancestors.of their ancestors.
 The terrestrial plants,The terrestrial plants,
which includewhich include
bryophytes (mosses) asbryophytes (mosses) as
well as the more highlywell as the more highly
evolved vascular plants,evolved vascular plants,
called tracheophytes.called tracheophytes.
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Introduction to PlantsIntroduction to Plants
 As a consequence of their move onto land, terrestrialAs a consequence of their move onto land, terrestrial
plants require structures that support their weight,plants require structures that support their weight,
prevent desiccation (drying out), aid in reproduction,prevent desiccation (drying out), aid in reproduction,
and transport water, nutrients, and the products ofand transport water, nutrients, and the products of
photosynthesis throughout the parts of the plant.photosynthesis throughout the parts of the plant.
 BryophytesBryophytes have not yet made the complete transitionhave not yet made the complete transition
to land, and are thus still dependent upon a moistto land, and are thus still dependent upon a moist
environment to assist in reproduction and nutrientenvironment to assist in reproduction and nutrient
transport.transport.
 The more highly evolvedThe more highly evolved tracheophytestracheophytes, on the other, on the other
hand, have developed internal systems of transport andhand, have developed internal systems of transport and
support calledsupport called vascular systemsvascular systems, which have allowed, which have allowed
them to becomes fully terrestrial.them to becomes fully terrestrial.
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Common Plant CharacteristicsCommon Plant Characteristics
 Plant bodies are divided into two regions, thePlant bodies are divided into two regions, the
underground root portion and the aerial shootunderground root portion and the aerial shoot
portion (including stem ,leaves, flowers, andportion (including stem ,leaves, flowers, and
fruits)fruits)
 These different regions of the plant areThese different regions of the plant are
dependent on each other, as each performsdependent on each other, as each performs
different essential functions.different essential functions.
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Common Plant CharacteristicsCommon Plant Characteristics
 Land plants also share certain more specific adaptationsLand plants also share certain more specific adaptations
that are essential to survival out of waterthat are essential to survival out of water
 These include an impermeable waxy cuticle on theThese include an impermeable waxy cuticle on the
other aerial surfaces, jacket cells around theother aerial surfaces, jacket cells around the
reproductive organs, and stomata that allow gasreproductive organs, and stomata that allow gas
exchange without risking excessive water loss.exchange without risking excessive water loss.
 All plants are alsoAll plants are also autotrophicautotrophic, meaning that they, meaning that they
produce their own food and do not use other organismsproduce their own food and do not use other organisms
to supply organic nutrients the way animals do.to supply organic nutrients the way animals do.
 Finally, the life cycle of plants follows a pattern calledFinally, the life cycle of plants follows a pattern called
the alternation of generations, in which they fluctuatethe alternation of generations, in which they fluctuate
between haploid and diploid generations and sexualbetween haploid and diploid generations and sexual
and asexual modes of reproduction.and asexual modes of reproduction.
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Plant ClassificationsPlant Classifications
 Terrestrial plants, as noted above, areTerrestrial plants, as noted above, are
classified as bryophytes and tracheophytes.classified as bryophytes and tracheophytes.
 Bryophytes, such as mosses and liverworts, areBryophytes, such as mosses and liverworts, are
still dependent on a moist environment forstill dependent on a moist environment for
reproductive and nutritive functions evenreproductive and nutritive functions even
though they are technically “terrestrial.”though they are technically “terrestrial.”
 Bryophytes also have very little internalBryophytes also have very little internal
support, limiting the heights to which they cansupport, limiting the heights to which they can
grow.grow.
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Common Plant Characteristics
 As explored in Common Plant Characteristics ,
most terrestrial plants (both bryophytes and
tracheophytes) share some general structural and
functional features.
 Plant bodies are divided into two regions, the
underground root portion and the aerial shoot
portion (including stem, leaves, flowers, and
fruits).
 These different regions of the plant are
dependent on each other, as each performs
different essential functions.
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Common Plant Characteristics
 Land plants also share certain more specific
adaptations that are essential to survival out of
water.
 These include an impermeable waxy cuticle on the
outer aerial surfaces, jacket cells around the
reproductive organs, and stomata that allow gas
exchange without risking excessive water loss.
 All Plants are also autotrophic, meaning that
they produce their own food and do not use other
organisms to supply organic nutrients the way
animals do.
 Finally, the life cycle of plants follows a
pattern called the alternation of generations, in
which they fluctuate between haploid and diploid
generations and sexual and asexual modes of
reproduction.
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Plant ClassificationsPlant Classifications
 Terrestrial plants, as noted above, areTerrestrial plants, as noted above, are
classified as bryophytes and tracheophytes.classified as bryophytes and tracheophytes.
 Bryophytes, such as mosses and liverworts, areBryophytes, such as mosses and liverworts, are
still dependent on a moist environment forstill dependent on a moist environment for
reproductive and nutritive functions evenreproductive and nutritive functions even
though they are technically “terrestrial.”though they are technically “terrestrial.”
 Bryophytes also have very little internalBryophytes also have very little internal
support, limiting the heights to which they cansupport, limiting the heights to which they can
grow.grow.
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Plant Classification
 As a phylum, Bryophytes, are lower on the
evolutionary scale than tracheophytes, which
have
adapted completely to life on land.
 Tracheophytes (also known as vascular plants)
possess well-developed vascular systems, which
are comprised of tissues that form internal
passageways through which water and dissolved
nutrients can traverse the entire plan
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 Vascular plants are thus far less reliant on
moist environments for survival.
 At the same time, Vascular systems also provide
a strong system of support to the plant, allowing
some tracheophytes to grow to immense heights.
 The tracheophytes can be further broken down
into two kinds of seed-producing plants,
gymnosperms (conifers) and angiosperms
(flowering plants).
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 The male gametes of gymnosperms and angiosperms are carried by
pollen each of these types of plants also produce seeds, which
protect the embryos inside from drying out in terrestrial
environment.
 Angiosperms, with their flowers and fruits, have adapted even
further to the terrestrial environment flowers, by attracting insects
and other pollen-bearing animals, aid in the transfer of pollen to
female reproductive organs.
 Angiosperm fruits, developed from ovaries, protect the seeds and
help in their dispersal.
 Finally, angiosperms themselves are divided into two classes--
monocots and dicots--based on differences in embryonic
development, root structure, flower petal arrangement, and other
factors.
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Structures and Functions
 The seed, which develops from an ovule after
fertilization has occurred, surrounds the plant
embryo and protects it from desiccation.
 Each seed consists of an embryo, food source,
and protective outer coat, and can lie dormant
for some time before germinating.
 The roots of a plant function in the storage of
nutrients, the acquisition of water and
minerals (from the soil), and the anchoring of the
plant to the substrate.
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Structures and Functions
 Tiny root hairs, which extend from the root
surface, provide the plant with a huge total
absorptive surface and are responsible for most of
the plant's water and mineral intake.
 Plant stems (or trunks, as they are called in
trees) function primarily in nutrient transport
and physical support.
 The leaves contain chlorophyll and are the
major sites of photosynthesis and gas exchange.
 Flowers contain the reproductive organs of
angiosperms.
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Essential Processes
 Plants carry out a number of processes that
are
essential to their survival.
 Internal water and sugar transport are largely
carried out within the vascular system,
ensuring that the entire plant receives water
and food even though these materials are
brought in or produced only in certain parts of
the plant.
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Essential Processes
 Plant hormones determine the timing and
occurrence of many of the processes of the
plant, from germination to tissue growth to
reproduction.
 Plants can also respond to light, touch, and
gravity in various ways.
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Life Cycle
 The life cycle of plants depends upon the
alternation of generations, the fluctuation
between the diploid (sporophyte) and haploid
(gametophyte) life stages.
 Reproduction in most plants can occur both
sexually and asexually.
 In sexual reproduction, fertilization occurs
when a male gamete (sperm cell) joins with an
egg cell to produce a zygote
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Life Cycle
 In gymnosperms and angiosperms (the seed plants), the
ovule containing the egg cell becomes a seed after
fertilization has occurred.
 In angiosperms (flowering plants), the embryo is given
added protection by an ovary, which develops into a fruit.
 Plants can also reproduce asexually through vegetative
propagation, a process in which plants produce genetically
identical offshoots (clones) of themselves, which then
develop into independent plants.
 This asexual means of reproduction can occur naturally
through specialized structures such as tubers, runners, and
bulbs or artificially through grafting
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