Plant Processes: Transpiration and Translocation
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Questions and Answers

If a plant is placed in an environment with ample sunlight but a limited supply of carbon dioxide, which of the following processes would be most directly affected?

  • The diffusion of water and mineral salts from the roots to the leaves.
  • The formation of three-carbon sugars (CH2O) in the dark reaction. (correct)
  • The splitting of water molecules into hydrogen and hydroxyl ions.
  • The trapping of solar energy by chlorophyll in the mesophyll cells.

Which of the following best describes the roles of both water and sunlight in photosynthesis?

  • Water provides the carbon atoms for sugar synthesis, while sunlight provides the energy to transport minerals.
  • Water regulates enzyme activity, while sunlight controls the opening and closing of stomata.
  • Water maintains turgor pressure in cells, while sunlight directly forms the structure of chlorophyll.
  • Water provides electrons for the light-dependent reactions, while sunlight provides the energy for carbon fixation. (correct)

A plant is subjected to a condition where the xylem vessels are damaged. How would this primarily affect the process of photosynthesis?

  • Reduced supply of carbon dioxide to the mesophyll cells.
  • Impaired function of enzymes involved in the dark reaction.
  • Decreased efficiency of photolysis due to lack of sunlight.
  • Limited transport of water and mineral salts to the leaves. (correct)

How does temperature most directly influence the rate of photosynthesis?

<p>By affecting the activity of enzymes involved in the various steps of photosynthesis. (C)</p> Signup and view all the answers

Which of the subsequent events would likely occur if a plant's chlorophyll production was significantly reduced?

<p>Decreased ability to convert solar energy into chemical energy. (A)</p> Signup and view all the answers

Which of the following is the most direct consequence of transpiration pull in plants?

<p>Passive absorption of water and mineral salts from the soil. (C)</p> Signup and view all the answers

How does the location and number of stomata relate to the rate of transpiration in plants?

<p>More stomata directly exposed to wind increase transpiration rates. (A)</p> Signup and view all the answers

If a plant exhibits a high rate of transpiration on a hot, dry day, which adaptive mechanism would best help it prevent excessive water loss, without compromising carbon dioxide uptake for photosynthesis?

<p>Developing a thicker cuticle layer on the leaves. (B)</p> Signup and view all the answers

Which of the following best describes the relationship between transpiration and translocation in vascular plants?

<p>Transpiration aids in water and mineral movement, while translocation distributes sugars. (D)</p> Signup and view all the answers

How might a drastic decrease in humidity affect the process of passive water absorption in plants?

<p>It would increase passive absorption due to a higher transpiration rate. (A)</p> Signup and view all the answers

If a plant is deficient in potassium (K), which process would be most directly hindered?

<p>Transport of sugars from leaves to storage organs. (A)</p> Signup and view all the answers

Why is proper water supply considered a vital factor influencing essential plant processes?

<p>It affects water and substance transport, transpiration, photosynthesis, and respiration. (D)</p> Signup and view all the answers

What would happen if you increased wind speed around a plant?

<p>It would increase transpiration. (B)</p> Signup and view all the answers

Under normal soil moisture conditions, what contributes to the absorption of water in plants?

<p>Positive root pressure (C)</p> Signup and view all the answers

What best describes the movement of elaborated sap within a plant?

<p>Bidirectional, through phloem from leaves to other parts of the plant (B)</p> Signup and view all the answers

What happens to the rate of water absorption when the soil becomes oversaturated (water replaces most of the air)?

<p>Absorption rate slows down (B)</p> Signup and view all the answers

What is the effect of temperatures above 40-45°C on water absorption in plants?

<p>Water absorption ceases (A)</p> Signup and view all the answers

What directly provides the energy required for water absorption and synthesis of organic substances in plants?

<p>Respiration (B)</p> Signup and view all the answers

Which of the following equations best represents plant respiration?

<p>$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy}$ (B)</p> Signup and view all the answers

Through what structures does respiration occur in woody stems?

<p>Lenticels (D)</p> Signup and view all the answers

What impact does an increase in carbon dioxide concentration have on the stomata?

<p>Causes the stomata to close (C)</p> Signup and view all the answers

Which of the following is NOT an internal factor affecting respiration?

<p>Mineral substances in the soil (C)</p> Signup and view all the answers

What is the primary function of photosynthesis?

<p>To convert light energy into chemical energy (B)</p> Signup and view all the answers

What are the primary reactants in the process of photosynthesis?

<p>Carbon dioxide and water (C)</p> Signup and view all the answers

Which part of photosynthesis involves the splitting of water molecules?

<p>Light Reaction (A)</p> Signup and view all the answers

What happens to hydroxyl ions (OH-) during the light reaction of photosynthesis?

<p>They are converted into water and oxygen (D)</p> Signup and view all the answers

What is the role of ATP and NADPH in the dark reaction of photosynthesis?

<p>To assimilate carbon dioxide (D)</p> Signup and view all the answers

In what way does the light reaction support the dark reaction in photosynthesis?

<p>By providing the ATP and NADPH required (A)</p> Signup and view all the answers

Flashcards

Transpiration

The process where plants circulate raw sap, remove excess water, prevent overheating, and exchange Oâ‚‚ and COâ‚‚.

Where Transpiration Occurs

Evaporation of water molecules through open stomata, lenticels or the cuticle.

Factors Influencing Transpiration

Factors such as root/leaf relationship, leaf structure, stomata location/number, light, humidity, temperature and wind.

Translocation

The process of moving organic substances (sugars) from source (leaves) to sink (rest of plant) via pholem tissue.

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Plant Vital Processes

Water and substance transport, transpiration, photosynthesis, and respiration.

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Root Absorption

Hairs absorb water/minerals, passing through cell membrane.

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Water Transport

Water and mineral salts are transported from root to the woody vessels (xylem).

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Passive Absorption

Water absorption driven by transpiration from the leaves.

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CH2O (Sugar)

A three-carbon compound (CH2O) formed during photosynthesis, serving as the base for creating sugars, fats, oils, and proteins.

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Stomata

Pores on leaves that facilitate the diffusion of carbon dioxide from the atmosphere into the intercellular spaces and mesophyll cells.

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Osmosis in Roots

The process by which water and mineral salts from the soil enter the plant roots through root hairs.

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Photolysis

The splitting of water molecules into hydrogen ions and hydroxyl ions using light energy, facilitated by chlorophyll.

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Chlorophyll

Green pigment in plant cells that captures solar energy and converts it into chemical energy during photosynthesis.

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Root Pressure

The positive pressure in plant roots that helps absorb water, especially under normal soil moisture conditions.

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Raw sap

Water and mineral substances absorbed by the root.

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Xylem

A plant tissue that transports raw sap (water and minerals) upwards from the roots to the leaves.

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Elaborated sap

Nutrient-rich (mainly sugars) fluid produced in the leaves by photosynthesis.

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Phloem

Plant tissue that transports elaborated sap (sugars) both upwards and downwards throughout the plant.

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Respiration

The process where plants absorb oxygen and release carbon dioxide, water and energy (ATP).

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Lenticels

Small structures on woody stems that facilitate respiration by allowing gas exchange.

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Photosynthesis

The process by which plants convert carbon dioxide and water into glucose (sugar) and oxygen using sunlight.

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Light Reaction

The first stage of photosynthesis, which requires sunlight to split water molecules.

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Dark Reaction

The second stage of photosynthesis, where carbon dioxide is assimilated (used to make sugar) using the energy from the light reaction.

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ATP

Molecule that provide energy for cell processes.

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NADP

Compound acting as a hydrogen and electron carrier in metabolic processes especially in cellular respiration.

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Study Notes

  • In the morning, leaves are strong; by noon, they droop and wilt.

Transpiration

  • Transpiration is vital for plant functions.
  • Facilitates raw sap from roots to leaves.
  • Removes excess water.
  • Prevents overheating.
  • Promotes Oâ‚‚ and COâ‚‚ exchange through stomata.
  • Occurs mainly through stomata, but also lenticels and leaf cuticles.
  • When stomata are open, water molecules evaporate.
  • Influenced by internal and external factors.

Internal Factors Affecting Transpiration

  • The relationship between root and leaf systems
  • the number and location of stomata
  • Leaf structure

External Factors Affecting Transpiration

  • Light
  • Humidity
  • Temperature
  • Wind

Translocation

  • Translocation moves organic substances, mainly sugars and nutrients, from leaves (source) to the rest of the plant (sink).
  • It occurs through the phloem tissue.

Plant Vital Processes

  • Water and substance transport
  • Transpiration
  • Photosynthesis
  • Respiration
  • These processes are affected by certain factors.

Water Supply

  • Root hairs absorb water and mineral salts through the cell membrane.
  • The cell membrane is permeable to certain substances.
  • Mineral substances from the soil include H, N, K, Ca, Mg, Fe, S, P in large quantities and Zn, Cu, Mo in small quantities.
  • Water and mineral salts move from absorbent pericarps to the root's central cylinder via woody vessels (xylem).

Water Absorption

  • Passive absorption is due to transpiration in the leaves, with about 98% of water released into the atmosphere.
  • Leaf cells become unsaturated, creating a transpiration pull.
  • In passive absorption, the leaf plays an active role.
  • Active absorption is independent of transpiration.
  • Under normal conditions, plants develop positive root pressure, aiding water absorption and conduction.
  • In active absorption, the root plays an active role.

Raw Sap

  • Water and minerals absorbed from the soil form raw sap.
  • Raw sap flows upwards through woody vessels (xylem) from root to leaves.

Elaborated Sap

  • Elaborated sap forms in the leaves through photosynthesis.
  • Elaborated sap flows through liberian vessels (phloem) both upwards and downwards.
  • The flow rate of elaborated sap through the phloem is slower than raw sap through the xylem.

Factors Influencing Substance Absorption and Circulation

Internal Factors

  • Root
  • Leaf

External Factors

  • Amount of water in the soil
  • Soil temperature
  • Air and soil chemical composition

Water Amount Effects

  • Water above 80% intensifies absorption.
  • Oversaturation slows absorption due to lack of air.
  • Insufficient water leads to stem deterioration and wilting.

Temperature Effects

  • Optimal temperature range is 20-32°C for maximum absorption.
  • Absorption ceases above 40-45°C.
  • Temperatures below 0°C decrease or stop absorption.

Respiration

  • Plants respire like all living organisms.
  • Respiration absorbs oxygen and releases carbon dioxide, water, and energy through the oxidation of organic compounds.
  • C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (ATP)
  • Respiration is vital for energy in synthesis, water absorption, growth, and movements.
  • The leaf is the primary respiration organ.
  • Atmospheric Oâ‚‚ enters through stomata, and COâ‚‚ is released.
  • Respiration occurs in roots through root hairs and in woody stems through lenticels.
  • Stomata opening is influenced by light, water, and carbon dioxide.
  • Normal COâ‚‚ concentration (0.03%) keeps stomata open; higher concentrations close them.

Internal Factors Affecting Respiration

  • Plant age
  • Organic substance quantity
  • Water content in the cell
  • Dormancy state of the plant

External Factors Affecting Respiration

  • Mechanical factors
  • COâ‚‚ and Oâ‚‚ concentrations
  • Mineral substances in the soil
  • Light
  • Temperature

Photosynthesis

  • Plants, algae, and some bacteria convert carbon dioxide and water into glucose, releasing oxygen, using sunlight.
  • Green plants manufacture their own food (organic compounds) using carbon dioxide and water in the presence of sunlight.
  • 6CO2 + 6H2O --sunlight/chlorophyll--> C6H12O6 + 6O2

Photosynthesis Mechanisms

Light Reaction

  • Light reaction happens in the day using chlorophyll to splits water into hydrogen and hydroxyl ions in photolysis.
  • 4H2O --Light/chloroplast--> 4H+ + 4OH-
  • Hydroxyl ions convert to water, releasing oxygen.
  • 4(OH-) → 2H2O + O2
  • NADP is reduced by hydrogen ion to NADPH, and ATP is formed

Dark Reaction

  • Dark reaction occurs at night, using ATP to assimilate carbon dioxide.
  • Enzymes form a three-carbon compound (CH2O) or sugar.
  • 4H+ + CO2 --enzymes--> CH2O + H2O
  • CH2O forms simple sugars, fats, oils, and proteins.

Requirements for Photosynthesis

  • Carbon dioxide diffuses into leaves through stomata.
  • Water and mineral salts are absorbed by root hairs and transported by xylem.
  • Sunlight is trapped by chlorophyll to split water in photolysis.

External Conditions

  • Carbon dioxide
  • Sunlight
  • Mineral salts
  • Water
  • Suitable temperature

Internal Conditions

  • Chlorophyll
  • Enzymes

Sunlight Importance

  • Sunlight splits water into hydrogen and hydroxyl ions in photolysis.

Optimum Temperature

  • Optimal temperature is needed for enzymes to function.

Chlorophyll

  • Chlorophyll captures solar energy and converts it to chemical energy.

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Description

Explore transpiration, a crucial plant process for water transport, cooling, and gas exchange. Learn about internal (root-leaf relation, stomata) and external factors (light, humidity) affecting it. Also, discover translocation, the movement of organic substances through the phloem.

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