Plant Physiology (Medical Entrance)

Essential macro elements (like nitrogen, phosphorus, potassium, etc.) are nutrients that plants must absorb from the soil in large quantities to survive.

Nitrogen deficiency in plants leads to chlorosis and premature leaf fall, as nitrogen is essential for chlorophyll production and protein synthesis.

Guttation is the exudation of drops of xylem sap on the tips or edges of leaves through specialized pores called hydathodes.

Chlorosis is the yellowing of leaf tissue due to a lack of chlorophyll, often caused by a deficiency of magnesium (a central component of chlorophyll) or iron (required for its synthesis).

Permanent wilting occurs when the soil water content drops to a level where the plant can no longer extract enough water to maintain turgor pressure. This is directly caused by the poor availability of water in the soil, even if the plant is physiologically healthy.

Chlorophyll is a magnesium-porphyrin complex. When the chlorophyll molecule breaks down, the central magnesium ion is released.

Molybdenum is essential for nitrogen metabolism. Its deficiency often manifests as interveinal chlorosis, mottling, and necrosis of leaves, particularly in older leaves first.

Major elements (macronutrients) include C, H, O, N, P, K, S, Ca, and Mg. Zinc (Zn) is a micronutrient required by plants in very small quantities.

Molybdenum is a key component of the enzyme nitrogenase, which is responsible for the biological fixation of atmospheric nitrogen into ammonia.

Dieback disease in citrus is a well-documented physiological disorder caused specifically by a deficiency of copper (Cu) in the soil.

Phosphorus is a critical component of ATP, nucleic acids, and phospholipids. It is well known for promoting vigorous root development in plants.

Carbon, oxygen, hydrogen, and nitrogen are the primary building blocks of organic molecules like proteins, carbohydrates, and lipids, making them the most abundant elements in living cells.

Potassium (K+) is the most abundant intracellular cation in plant cells and plays a vital role in maintaining osmotic potential and enzyme activation.

 Xylem tissue is involved in water conducting system of plants; so if it is blocked, the plant will show wilting. The process of wilting modifies the leaf angle distribution of the plant (or canopy) towards more erectophile conditions.

When a plant is incinerated, the organic matter (carbon, hydrogen, oxygen, nitrogen) is oxidized and lost as gases. The remaining ash consists of the inorganic mineral salts that were absorbed from the soil.

The starch-sugar interconversion theory, which explains stomatal movement based on the osmotic changes resulting from starch hydrolysis to glucose, was proposed by Sayre and later supported by Steward.

Phosphorus is central to energy metabolism because it is a key component of ATP (adenosine triphosphate), the universal energy currency of cells.

Most transpiration occurs through the stomata located in the epidermis (dermal tissue) of leaves.

The raised water table results in the soils becoming water-logged. When soils are water-logged, air spaces in the soil are filled with water, and plant roots essentially suffocate - lack oxygen. Waterlogging also damages soil structure. So, the soil becomes physiologically dry.

Plasmolysis is the process where a cell loses water to a hypertonic environment. This loss of water from the cell to the outside is called exosmosis.

The relay pump theory, which suggests that living cells in the xylem parenchyma act as pumps to move sap upward, was proposed by Godlewski and Westermeyer.

The plasma membrane is selectively permeable, regulating the entry and exit of water and various solutes to maintain cellular homeostasis.

Water moves from a region of lower osmotic pressure (higher water potential) to a region of higher osmotic pressure (lower water potential) across a semipermeable membrane. Therefore, solvent moves from B (5 atm) to A (10 atm).

Deplasmolysis is the reversal of plasmolysis, which occurs when a plasmolyzed cell is placed in a hypotonic solution, causing water to enter the cell (endosmosis) and restore turgor.

Plastocyanin is a copper-containing protein that functions as an electron carrier in the photosynthetic electron transport chain.

Water absorption by roots is an active process influenced by metabolic activity, which is optimal at moderate temperatures, typically between 20 and 35 degrees Celsius.

Monotropa (Indian pipe) is a non-photosynthetic plant that obtains nutrients from decaying organic matter, making it a saprophyte. Nepenthes, Utricularia, and Dionaea are insectivorous plants.

Transpiration is the evaporation of water from plants. Higher temperatures increase the rate of evaporation, thereby enhancing the rate of transpiration.

Iron is essential for chlorophyll synthesis. Since iron is relatively immobile in plants, its deficiency symptoms, such as interveinal chlorosis, appear first in young leaves.

Heart rot in sugar beet and turnip is a classic symptom of boron deficiency, which affects cell division and structural integrity.

The Cohesion-Tension theory, which is the most widely accepted explanation for the ascent of sap, was proposed by Dixon and Jolly.

Root pressure is the positive pressure that develops in the roots of plants due to the active absorption of mineral nutrients. A manometer is the standard instrument used to measure this pressure.

High relative humidity reduces the water vapor gradient between leaf and atmosphere, decreasing transpiration. High wind velocity increases transpiration by removing the boundary layer. High temperature and adequate soil water both increase transpiration.

A cell swells when placed in a hypotonic solution because the concentration of solutes is lower outside the cell than inside, causing water to move into the cell via osmosis.

Potassium ions (K+) are essential for stomatal regulation. The influx and efflux of potassium ions in guard cells change their turgor pressure, leading to the opening and closing of stomata.