46. ​​Plant Physiology

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Plant Physiology is an important topic in Biology, especially for those preparing for ENEM. This chapter covers the vital processes that occur in plants, including photosynthesis, respiration, water and nutrient transport, growth and development, and responses to environmental stimuli.

Photosynthesis

Photosynthesis is the process by which green plants, algae, and some bacteria convert sunlight, carbon dioxide, and water into glucose and oxygen. It occurs mainly in the leaves of plants, where chlorophyll (the green pigment that absorbs light) is present. This process is vital for life on Earth as it is the main source of oxygen and also the basis for the food chain.

Photosynthesis occurs in two main stages: the light phase and the dark phase. In the light phase, light energy is used to split water molecules, releasing oxygen. In the dark phase, carbon dioxide is converted to glucose via the Calvin Cycle.

Breathing

Respiration is the process by which plants break down glucose to produce energy in the form of ATP. This process is the opposite of photosynthesis and occurs mainly at night when there is no sunlight available for photosynthesis. Respiration occurs in three steps: glycolysis, the citric acid cycle (or Krebs cycle) and the electron transport chain.

Transport of water and nutrients

Plants transport water and nutrients from their roots to other parts of the plant through xylem, a type of vascular tissue. This process is known as sweating. Water is drawn up the plant through water tension created by evaporation of water from the leaves. Nutrients are transported from their roots through phloem, another type of vascular tissue, in a process known as translocation.

Growth and development

The growth and development of plants is regulated by plant hormones such as auxins, gibberellins, cytokinins, abscisic acid and ethylene. These hormones control processes such as cell division, cell elongation, cell differentiation, seed dormancy, flowering, leaf fall and fruit maturation.

Responses to environmental stimuli

Plants have the ability to respond to various environmental stimuli, a phenomenon known as tropism. For example, phototropism is the response of plants to light, while geotropism is the response to gravity. Plants can also respond to stimuli such as water (hydrotropism), touch (thigmotropism) and chemicals (chemotropism).

In summary, Plant Physiology is a fascinating field that explores the vital processes that allow plants to survive and thrive. Understanding these processes not only helps us better understand the natural world, it also has practical implications in areas such as agriculture, horticulture, and environmental conservation.

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