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Plant Ecology

• Plant ecology is the study of the relationships between plants and their environment.
• It examines interactions between organisms and their surroundings.
• Ecology studies organisms from the individual level up to the biosphere.

Levels of Organization

• Atom
• Molecule
• Organelle
• Cell
• Tissue
• Organ
• Organ systems
• Organism
• Population
• Community
• Ecosystem
• Biosphere

Plant Ecology Branches

• Plant Ecology: Studies the relationships between plants and their environment.
• Animal Ecology: Studies the relationships between animals and their environment.
• Microorganism Ecology: Studies the relationships between microorganisms and their environment.

Environmental Factors

• Environmental factors are complex factors that affect organisms.
• These include: soil, water, wind, gravity, light, temperature, and other living organisms.
• Environmental factors can be categorized into four groups:
  • Climatic factors
  • Edaphic factors (soil)
  • Topographic factors (terrain, location)
  • Biotic factors

Climatic Factors

• Temperature (including tropical, subtropical, temperate, cool, polar)
• Seasons
• Light
• Wind
• Humidity
• Rainfall
• These factors vary across regions and even within the same region

Thermal Factors

• Temperature is a form of energy sourced from the sun.
• Global temperature patterns influence an ecosystem's characteristics.
• Temperature varies due to latitude, altitude, slope, and daily/annual cycles of Earth's orbit around the sun.
• High temperatures at the equator, lower temperatures at higher latitudes.
• Aquatic environments experience smaller temperature variations than terrestrial environments.
• Factors affecting temperature variation on land include proximity to bodies of water, ice cover, topography, wind patterns, and plant cover.

Thermal Stress

• Plants experience thermal stress when exposed to temperatures unsuitable for their growth.
• High or low temperatures disrupt vital plant processes, limiting their distribution.
• Extreme temperature fluctuations impact cellular components like the cytoplasm and chloroplasts and the photosynthetic process.
• Prolonged stress leads to membrane damage and cellular death, eventually killing the plant.
• Adverse impacts include water loss due to increased transpiration, imbalance between respiration and photosynthesis, the production of toxic substances within the plant due to metabolic disruptions, and damage to crucial plant proteins and chloroplasts, which results in leaf discoloration and stunted growth.

Plant Adaptation to Thermal Stress

• Avoidance strategies (reducing exposure to extreme temperature fluctuations)
• Tolerance strategies (adjusting internal processes to withstand temperatures)
• Physiological changes (adjusting biochemical processes to maintain optimal functioning)
• Morphological adjustments (e.g., modifications in leaf structure).

Light and Plant Growth

• Light is essential for photosynthesis, converting light energy into chemical energy.
• Plants absorb and utilize visible light (especially red and blue wavelengths) for photosynthesis.
• Light intensity and duration influence plant development, growth, and distribution.
• Shade tolerance vs. sun-loving characteristics differ across plant species.
• Light availability affects chlorophyll production, leaf structure, and overall plant physiology.
• Increased light intensity leads to thicker cuticles, small leaves, and high amounts of palisade tissue.

Etiolation

• Etiolation: A plant response to decreased light. This results in less chlorophyll production, elongated stems, and pale coloration.
• Plants in shaded areas may exhibit etiolation, which limits their ability to photosynthesize efficiently.

Photoperiodism

• Photoperiodism is a plant's response to light duration. It triggers seasonal changes in plant growth and development.
• Short-day, long-day, and day-neutral plants differ in their response to light.

Stomatal Regulation

• Light is a major factor in regulating stomatal opening and closing.
• Stomatal opening and closing are influenced by the osmotic potential of guard cells.
• Changes in osmotic potential modify water movement in guard cells, affecting stomatal aperture.
• At night, sugars convert to starch, decreasing water uptake and causing stomata closure.

Other Factors

• Temperature and light significantly influence a plant's growth patterns, its composition and its susceptibility to disease.
• Variations in light and temperature interact to affect the rate of photosynthesis and respiration and ultimately influence development.