IB BIO I
Van Roekel
Plant Science
Part of the Kingdom Plantae, and can be divided into multiple categories based on structures and
tissues
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Non-vascular
o No conducting tissues/vascular tisssue
o Grouped as Bryophytes or Chlorophytes
o Grow small and close to ground
o i.e. Mosses, liverworts and hornworts
Seedless Vascular Plants
o Well-developed vascular tissue
o Grouped as Filicophytes
o Do not produce seeds
o i.e. Includes Ferns, club mosses, horsetails
Seeded Vascular Plants
o Includes most living plant species.
o Grouped as spermatophytes
o Seeds are an embryo, supply of nutrients and a protective outer coat.
o Extensive network of vascular tissue. Includes some of the worlds largest organisms.
Two types of Seeded Vascular Plants:
o Gymnosperms - Have seeds that do not develop within an enclosed structure.
o Angiosperms - Have seeds that develop within an enclosed structure.
3 types of tissues in Angiosperms
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Dermal Tissue – outer protective covering (skin) of plant.
o Protects from physical agents and pathogens.
o Prevents Water loss
Ground Tissue – Consists mostly of thin-walled cells
o Function in storage, photosynthesis, support and secretion.
Vascular Tissue – transport nutrients and provides structure and support
o Xylem carries water and minerals from roots to leaves
o Phloem transports organic nutrients throughout plant
Meristematic Tissue
o Meristematic Tissue is composed of clusters of small cells with the same function as
stem cells
o When they divide, one remains meristematic (initials), while the other is free to
differentiate and become a part of the plant body (derivatives)
3 types of organs in plants (recognize diagrams of each from powerpoints)
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Root Tissue/Organs
o Function to absorb mineral ions and water from soil, anchor the plant, and provide food
storage
o Epidermis – protective outer layer
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Cortex – involved in conducting water from soil to interior vascular tissue, and may also
store food
Endodermis – surround vascular tissue
Vascular tissue includes xylem and phloem
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Stem tissue/organs
o Region of plant where leaves are attached
o Area where leaf joins stem is the node, area between two nodes is an internode
o Epidermis – protection and may have pores (lenticels) that allow for gas exchange
o Transporting tissue/Vascular tissue (xylem and phloem) transport and support
o Cortex – supports and storage
o Cambium – area of rapidly dividing cells that differentiate into xylem and phloem
o Central Pith – region of storage and support area
o Turgid, fluid filled cells in cortex and pith offer support to the plant
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Leaf Tissue/Organ
o Function in photosynthesis
o Vary greatly in form but generally contain and blade (flattened part) and stalk (connects
to stem)
o Cuticle – layer of wax that protects against water loss and insect invasion
o Vascular tissue –xylem brings water to leaves, phloem varies products of photosynthesis
to rest of plant. These occur together in veins or vascular bundles
o Palisade mesophyll – upper portion of leaf consists of densely packed cells with large
number of chloroplasts to perform photosynthesis
o Spongy Mesophyll – bottom portion of leaf is composed, consists of loosely packed cells
with few chloroplasts
o Stomata – allow for gas exchange of O2 and CO2
o Guard Cells – guard opening and closing of stomata
2 types of Angiosperms based on morphological (structural) characteristics
Monocot
Parallel venation in leaves
3 flower parts (multiples of 3)
Seed contains only one cotyledon (seed leaf)
Vascular bundles arranged throughout the stem
and in a ring formation in roots
Root system mainly fibrous
Pollen grain with one opening
Dicot
Net-like venation in leaves
4 or 5 flower parts (multiples of 4/5)
Seeds contain 2 cotyledons (seed leaves)
Vascular bundles arranged in ring in the stem and
in a cross formation in the roots
Root system involves a taproot (main root)
Pollen grain with 3 openings
Plant Growth
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Apical Meristem – Occurs at tip of root and stems.
o Produces primary growth (roots extend into soil and stem grows longer) and primary
tissue.
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Lateral Meristem – Allows for secondary growth (growth in thickness of plants).
o Vascular Cambium – lies between xylem and phloem
o Cork cambium – occurs within the bark of a plant.
Tropism is the growth or movement in responses to external stimuli
Phototropism – plant growth in response to light
o Stems exhibit positive phototropism (move towards light)
o Roots exhibit negative phototropism (move away from light)
Transport in Plant
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Water Transport
o Epidermis  Cortex  Vascular Cylinder where capillary action carries it up stem
o “Tiger” Pressure
 a) Water enters the cell by osmosis from the lower solute concentration to
higher solute concentration
 b) The volume of the cell cytoplasm increases forcing the plasma membrane
outwards against the cell wall. A pressure develops called the turgor pressure
(pressure potential), which is excerpted against the cell wall.
 c) The outward pressure is matched by an inward pressure, equal in magnitude
but opposite in direction
Selective Ion Transport
o 3 Major Processes that allow Ions to pass from soil to root:
o Diffusion of mineral ions with mass flow of water down concentration gradient
o Fungal Hyphae – symbiotic relationship between plant roots and fungi to absorb
mineral
o Active Transport – proton pump uses energy pump against concentration gradient
Transpiration - Loss of water vapor from leaves and other aerial parts of the plant.
o 90% of water absorbed is lost via transpiration
o Factors that affect transpiration
 Light – speeds it up by opening stomata
 Humidity – decreasing humidity increases it
 Wind – increases it by carrying air away
 Temperature – increases transpiration as temp. increases
 Soil – if intake is low, stomata close to keep water in/decreases transpiration
 Carbon Dioxide – high CO2 causes stomata to close and decrease transpiration
o The stomata change based on changes in turgor pressure. In excess water, guard cells
swell and thus open stoma. When water is not present, guard cells close stoma.
Reproduction in Angiosperms
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The flower is the reproductive structure of angiosperm
All angiosperms have flowers that attract pollinators
(insects, birds, etc), which allow transfer of male pollen
to female reproductive portions for fertilization
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Flower Structure
o Sepals – protect the developing flower while in the bud
o Petals – often colorful to attract pollinators
o Stamen – male reproductive organ
 Anther – part of stamen which produces the male sex cells, pollen
 Filament – stalk of the stamen that holds anther
o Carpel – female reproductive organ (can be referred to as pistil)
 Stigma – sticky top of carpel on which pollen lands
 Style – structure of carpel that supports the stigma
 Ovary – base of carpel in which female sex cells develop
Alternation of Generation
o All plants show two different generations in their life cycle
o Gametophyte generation (haploid)
 Produces plant gametes by mitosis
o Sporophyte generation (diploid)
 Produces spores by meiosis
Pollination
o Pollination is the process by which pollen is placed on the stigma
 By pollinators (insects, birds, wind, etc…)
 Self-pollination – pollen from anther falls on its own stigma  less genetic
variety
 Cross-pollination – pollen is carried from one anther of a plant to the stigma of
another plant more genetic variety
Fertilization
o Fertilization happens when male and female sex cells unite and form a diploid organism
called a zygote
o Occurs in the ovary of carpel
o Once a zygote is formed, it develops surrounding tissue into the seed
Seeds
o The seed is the means by which an embryo can be dispersed to distant locations
o Testa – tough, protective seed coat
o Cotyledons – seed leaves that function as nutrient storage
o Micropyle – scar of opening where pollen fertilized ovule (egg)
o Embryo shoot – become new stem when plant germinates (sprouts/grows)
o Embryo root – becomes new root when plant germinates (sprouts/grows)