Plant nutrients are divided into macronutrients and micronutrients based on the quantity required. Carbon, oxygen, and nitrogen are essential macronutrients needed in large amounts for structural and metabolic functions. Boron is a micronutrient, required by plants in very small trace amounts for processes like cell wall formation, pollen germination, and sugar translocation.

Sunhemp (Crotalaria juncea) is a leguminous plant widely used as a green manure crop in India. It is incorporated into the soil while still green to increase nitrogen content and organic matter, thereby improving soil structure and fertility for subsequent crops.

Albinism in plants refers to the complete absence of chlorophyll, resulting in white or pale leaves. While chlorosis is the yellowing of leaves due to chlorophyll deficiency, the total loss of pigment is specifically termed albinism. This condition is often genetic and prevents the plant from performing photosynthesis, usually leading to the death of the seedling unless it is parasitic.

Urea is a highly concentrated nitrogen source, but it is prone to rapid loss through volatilization (as ammonia gas), high water solubility leading to runoff, and leaching into groundwater. Briquetting or deep placement of urea helps control its release rate, ensuring that nitrogen remains available to the plant roots for a longer period, thereby increasing fertilizer efficiency.

The 'white tip' or 'white bud' condition in maize is a classic symptom of zinc (Zn) deficiency. Zinc is essential for the synthesis of tryptophan, a precursor to the plant growth hormone auxin. When zinc levels are insufficient, leaf development is stunted, and the tips of the leaves become chlorotic or white. This nutrient is crucial for various enzymatic activities and overall plant growth regulation.

Fertigation is a specialized irrigation technique that combines fertilization with irrigation. By dissolving fertilizers in the irrigation water, nutrients are delivered directly to the root zone of the plants, which increases nutrient use efficiency and reduces the labor required for manual application.

Plants typically absorb nitrogen in inorganic forms such as nitrates (NO3-) and nitrites (NO2-), or as ammonium ions. They can also assimilate nitrogen from organic compounds found in the soil. While nitrogen gas is abundant in the atmosphere, most plants cannot fix it directly and rely on symbiotic bacteria or soil processes to convert it into usable forms.

Spongy tissue is a major physiological disorder characterized by the development of an acidic, sour, and spongy pulp in mangoes, particularly affecting the Alphonso variety. This condition is caused by the breakdown of starch and the accumulation of organic acids, which renders the fruit unsuitable for export. It is a significant concern for the Indian mango industry, specifically regarding the premium Alphonso cultivar.

Phosphorus is highly mobile within the phloem of plants. It can be readily translocated from older, mature leaves to younger, developing tissues or reproductive organs when the plant experiences a deficiency, allowing the plant to prioritize growth in critical areas.

Prophylaxis in plant pathology refers to preventive measures taken to protect plants from infection. This includes strategies such as quarantine, sanitation, and the use of protective barriers or chemical sprays to ensure that the pathogen does not reach the host plant, thereby preventing the disease cycle from initiating.