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Biology > Topic 9 - Plant science > Flashcards

Topic 9 - Plant science Flashcards

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1
Q

Draw a diagram to show the distribution of tissues in the leaf of a plant

A
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2
Q

Draw a diagram to show the distribution of tissues in the stem of a plant

A
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3
Q

Outline the differences between the structures of dicotyledonous and monocotyledonous plants

A
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4
Q

How does the distribution of tissues help the function of the leaf in dicotyledonous plants?

A
  • The waxy cuticle prevents loss of water and insect invasion
  • The vascular bundles are located in the middle of the leaf to provide easy access to everywhere in the leaf
  • Palisade mesophyll on the upper side consists of densely packed chloroplasts to ensure efficient photosynthesis (this side is exposed to sunlight)
  • Spongy mesophyll on the lower side have loosely packed cells with few chloroplasts and lots of air spaces for efficient gas exchange
  • Stomata on the bottom surface allow oxygen and carbon dioxide exchange from the bottom side (less water lost)
  • Guard cells around the stomata control the opening and closing of them
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5
Q

Describe storage roots

A
  • Specialised cells within the root store large quantities of carbohydrates and water
    e. g. carrots and beets
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6
Q

Describe bulbs

A
  • Vertical, underground stems consisting of enlarged bases of leaves that store food
    e. g. onions
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7
Q

Describe stem tubers

A
  • Horizontally growing stems below ground that are modified as carbohydrate-storage structures
    e. g. potatoes
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8
Q

Describe tendrils

A
  • Modified leaf structures that coil around objects to aid in support and climbing (may also be formed from modified stems)
    e. g. pea plants
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9
Q

What kind of meristems do dicotyledonous plants have?

A

Apical and lateral

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10
Q

What is meristem?

A

Undifferentiated tissue that can initiate further growth

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11
Q

What are apical meristems?

A
  • Tissue that occurs at the tips of roots and stems of plants
  • Produces primary tissues and causes primary growth
  • Allows the root to extend to the soil and also allows the stem to grow longer
  • Increases exposure to light and carbon dioxide
  • Results in herbaceous, non-woody stems and roots
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12
Q

What are lateral meristems?

A
  • Allow growth in thickness of plants
  • Secondary growth
  • Most treems and shrubs have active lateral meristems

Two types:

  • Vascular cambium produces secondary vascular tissue → on the inside it produces secondary xylem and on the outside produces secondary phloem
  • Cork cambium occurs within the bark of a plant and produces the cork cells of the outer bark
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13
Q

What is auxin?

A

A plant hormone that causes positive phototropism of plant shoots and seedlings

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14
Q

How does auxin control plant growth and create phototropism?

A

When exposed to light, auxin becomes redistributed to the stem side away from the light source and excess growth on that side of the plant. This causes the plant to curve towards the light source, thus receive more light.

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15
Q

How does the root system provide a large surface area for mineral ion and water uptake?

A

They branch and grow root hairs which further increase the total surface area.

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16
Q

In what ways can mineral ions in the soil move to the root?

A
  1. Diffusion
  2. Aid provided by fungal hyphae (mutualism)
  3. Mass flow of water in the soil carrying ions
17
Q

Explain the process of mineral ion absorption from the soil into roots by active transport

A
  1. Proton pump uses energy from ATP to pump hydrogen ions out of the cell
  2. A concentration gradient of hydrogen ions is created outside the cell → cell has a negative charge
  3. Gradien results in the diffusion of hydrogen ions back into the cell
  4. The voltage difference is called a membrane potential
  5. The hydrogen ion gradient and the membrane potential represent forms of potential energy that can be used to absorb mineral ions
18
Q

How do terrestial plants support themselves?

A
  • Thickened cellulose → cell wall is stronger
  • Cell turgor pressure → pressure exerted on the cell wall by the plasma membrane, due to water inside the cell
  • Lignified xylem → branched polymer, lignified cells have much incraesed supportive capabilities
19
Q

What is transpiration?

A

The loss of water vapour from the leaves and stems of plants.

20
Q

How does water move by the transpiration stream in plants?

A
  • Xylem vessels contain long unbroken columns of water (held together by hydrogen bonds)
  • During transpiration, water moves upwards from the roots to the leaves (transpiration stream)
  • Mature xylem vessels are dead, flow of water is passive
  • Adhesion sticks water to the wall of xylem
    1. Heat causes evaporation of water from spongy mesophyll
    2. Water that evaporates is replaced with water from xylem vessels (capillary action)
    3. Suction is created inside xylem vessels when water is pulled out (transpiration pull)
    4. Columns of water don’t break due to cohesion
    5. Basically the whole column of water moves upwards molecule by molecule, each molecule pulling another molecule from the roots ‘til exiting from the leaf
21
Q

What is the function of guard cells?

A

They can regulate transpiration by opening and closing stomata

22
Q

Which hormone causes the closing of stomata?

A

Abscisic acid.

23
Q

How do light, temperature, wind, and humidity affect the rate of transpiration?

A

Light: speeds up transiration by warming the leaf and opening stomata

Temperature: increasing temperature causes greater transpiration because more water evaporates

Wind: increases the rate of transpiration because humid air near the stomata is carried away (the wind catches water molecules)

Humidity: decreasing humidity increases transpiration because of the greater difference in water concentration

24
Q

What are adaptations of xerophytes that help them reduce transpiration?

A
  1. Reduced leaves reduce water loss by decreasing surface area
  2. Hair-like cells on the leaf surface trap a layer of water vapour
  3. Deep roots
  4. Thickened waxy cuticle
  5. Reduced number of stomata decreases water loss
25
Q

What is the role of phloem in active translocation of sugars and amino acids?

A
  • Phloem cells use energy for active translocation
  • Substances are translocated from sources to sinks
  • Sources are e.g. stems and leaves
  • Sinks are e.g. roots and growing fruits
26
Q

Draw the structure of a dicotyledonous flower

A
27
Q

What is pollination?

A

The transfer of pollen from an anther to a stigma.

28
Q

What is fertilisation?

A

The fusion of a male gamete with a femal gamete inside the ovule.

29
Q

What is seed dispersal?

A

The function of the fruit: to disperse seeds

30
Q

Draw a diagram of the external and internal structure of a dicotyledonous seed

A
31
Q

What are the conditions needed for the germination of a typical seed?

A
  • Water must be available to rehydrate the dry tissues of the seed
  • Oxygen must be available for aerobic cell respiration
  • Suitable temperatures are needed for specific enzyme activity
32
Q

What are the metabolic processes during the germination of a starchy see?

A
  1. The absorption of water and the rehydration of living cells. This allows the cells to become metabolically active
  2. A plant growth hormone called gibberellin is produced in the cotyledons of the seed
  3. Gibberellin stimulates the production of amylase, which catalyses the digestion of starch into maltose in the food stores of the seed
  4. Maltose is transported from the food stores to the growth regions of the seedling, including the emryo root and the embryo shoot
  5. Maltose is converted into glucose, which is used in aerobic cell respiration or to synthesise cellulose or other substances needed for growth
33
Q

How is flowering controlled in short-day and long-day plants?

A
  • Length of the night is significant
  • Short-day plants only flower when they receive a long continuous period of darkness
  • Long-day plants only flower when they receive a short period of darkness
34
Q

What is the role of phytochrome in the controlling of flowering?

A
  • Phytochrome is a pigment that can be used to measure the length of day
  • Exists in two interconvertible forms, Pr and Pfr
  • Pr is the inactive form, when it absorbs red light it is rapidly converted into the active form, Pfr
  • In darkness Pfr slowly reverts back to Pr
  • This gradual reversion process is how the length of the dark period is measured
  • Enough Pfr remains in long-day plants stimulates flowering
  • In short-day plants, Pfr acts as an inhibitor of flowering

Biology (13 decks)

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