Water, Mineral, and Nitrogen Exchange in Plants

Water, Mineral, and Nitrogen Exchange in Plants

Water and Mineral Absorption:

• Root hairs are specialized cells on plant roots that create a large surface area for contact between the roots and the soil, facilitating the absorption of water and mineral ions.

• Water is absorbed into the roots through osmosis, which involves the movement of water from a region of high water concentration to a region of low water concentration.

• Dissolved substances are absorbed by plant roots through various mechanisms: diffusion, active transport, and passive transport.

Water Transport to Leaves:

• Root pressure provides the initial driving force, pushing water from the roots up the plant stem.

• Transpiration pull creates the upper driving force, pulling water from the stem to the leaves.

• Leaves are the primary sites of transpiration, which helps cool the leaves, open stomata for CO2 uptake, and create the upper force to pull water from the roots.

• Stomata are specialized cells that regulate the rate of transpiration.

• If the amount of water transpired is greater than the amount of water absorbed, the plant will dehydrate.

Roles of Mineral Elements:

• Macronutrients are elements required by plants in large amounts: C, H, O, N, P, S, K, Mg, Ca.

• Micronutrients are elements required by plants in small amounts: Fe, Mo, B, Mn, Cl, Zn, Cu, Ni.

• Chlorophyll is composed of the elements: C, H, O, N, Mg.

• Proteins are composed of the elements: C, H, O, N.

• Nucleic acids (RNA, DNA) are composed of the elements: C, H, O, N, P.

Nitrogen Absorption and Assimilation:

• Plant roots absorb nitrogen in the form of NH4+ and NO3-.

• When NO3- enters the roots, it is reduced to NH4+.

• In plant tissues, NH4+ is assimilated through three main pathways: amination, transamination, and amide formation.

Fertilizing Plants:

• There are two methods of fertilizing plants: foliar application and root application.

• When applying fertilizer to leaves, it should be done when the weather is not rainy or too sunny.

• When fertilizing plants, it is important to consider the growth characteristics of the plant, its developmental stage, climate conditions, and soil properties.

• Excessive fertilization can poison the plant, contaminate agricultural products, pollute the environment, reduce crop yields, and disrupt the plant’s growth processes.

Soil Improvement:

• Soil can be improved through various methods:

• Planting legumes to replenish soil nitrogen.

• Applying lime and manure to improve acidic soils.