Plant Nutrition and Soil Ecosystems

How do most plants obtain CO2 and nutrients?

Plants take up CO2 from the air through the shoot system and water and nutrients from the soil through the root system.

What adaptation do some plants in nutrient-poor soils use?

Some plants, like Genlisea, use carnivory to obtain mineral nutrients.

What are the basic physical properties of soil?

The basic physical properties of soil are texture and composition.

What are the three classifications of soil particles by size?

Soil particles are classified as sand, silt, and clay.

What is the role of humus in soil?

Humus retains water, increases cation exchange capacity, and serves as a reservoir of mineral nutrients.

What is topsoil composed of?

Topsoil consists of mineral particles, living organisms, and humus.

What is cation exchange in soil?

Cation exchange is the process where cations are displaced from soil particles by other cations, allowing them to enter the soil solution for plant uptake.

What is the effect of soil pH on mineral availability?

Soil pH affects cation exchange and the chemical form of minerals; cations are more available in slightly acidic soil.

What is the significance of loams in agriculture?

Loams are the most fertile topsoils and contain equal amounts of sand, silt, and clay, making them ideal for plant growth.

What are the consequences of soil mismanagement?

Soil mismanagement can deplete mineral content, tax water reserves, and encourage erosion, leading to reduced agricultural productivity.

What is the primary source of irrigation water?

The primary source of irrigation water is underground water reserves called aquifers.

What is salinization and its impact on soil?

Salinization is the concentration of salts in soil due to evaporation, which reduces water potential and diminishes water uptake by plants.

What is the goal of sustainable agriculture?

The goal of sustainable agriculture is to use farming methods that are conservation-minded, environmentally safe, and profitable.

What is phytoremediation?

Phytoremediation is a biological technology that reclaims contaminated areas by growing plants that can extract soil pollutants.

How do roots contribute to soil acidity?

Roots acidify the soil solution, which helps in the displacement of cations from soil particles.

What percentage of a plant's fresh mass is water?

80-90% of a plant's fresh mass is water.

What elements make up 96% of a plant's dry mass?

96% of a plant's dry mass comes from CO2 assimilated into carbohydrates during photosynthesis.

What is the impact of excess minerals in soil?

Excess minerals can leach from the soil and cause algal blooms in lakes.

What are the main inorganic components of soil?

Inorganic components include cations like K+, Ca2+, and Mg2+ that adhere to negatively charged soil particles.

What is the effect of water and wind erosion on soil?

Water and wind erosion cause topsoil removal and loss of soil nutrients.

What practices can reduce soil erosion?

Practices include planting trees as windbreaks, terracing, cultivating in contour patterns, and no-till agriculture.

How many chemical elements are identified in plants?

More than 50 chemical elements.

What are the essential elements required for a plant to complete its life cycle?

17 essential elements.

What technique do researchers use to determine essential chemical elements for plants?

Hydroponic culture.

What are macronutrients?

Nine essential elements that plants require in relatively large amounts.

List the macronutrients essential for plant growth.

Carbon, oxygen, hydrogen, nitrogen, phosphorus, sulfur, potassium, calcium, and magnesium.

Which macronutrient contributes the most to plant growth and crop yields?

Nitrogen.

What are micronutrients?

Essential elements that plants need in very small amounts.

List the micronutrients required by plants.

Chlorine, iron, manganese, boron, zinc, copper, nickel, and molybdenum.

Which additional nutrient is required by plants with C4 and CAM photosynthetic pathways?

Sodium.

What is the function of micronutrients in plants?

They function as cofactors, nonprotein helpers in enzymatic reactions.

How do symptoms of mineral deficiency vary in plants?

They depend on the nutrient's function and mobility within the plant.

What is the effect of a mobile nutrient deficiency in plants?

It usually affects older organs more than young ones.

What is the effect of a less mobile nutrient deficiency in plants?

It usually affects younger organs more than older ones.

Which mineral deficiencies are the most common in plants?

Nitrogen, potassium, and phosphorus deficiencies.

What is the role of rhizobacteria in plant nutrition?

They enhance plant growth by producing antibiotics, absorbing toxic metals, converting nitrogen, and stimulating growth.

What is the rhizosphere?

The layer of soil closely surrounding the plant's roots.

What is the nitrogen cycle?

A series of natural processes that transform nitrogen and nitrogen-containing compounds.

How do plants primarily acquire nitrogen?

As nitrate (NO3-).

What is nitrification?

The two-step process where nitrifying bacteria oxidize ammonia to nitrite and then to nitrate.

What happens to some soil nitrogen in the nitrogen cycle?

It is lost to the atmosphere when denitrifying bacteria convert nitrate to gaseous nitrogen (N2).

What mutualistic relationship do plants have with mycorrhizal fungi?

Most plant species are associated with mycorrhizal fungi that enhance nutrient uptake.

What mutualistic relationship exists between leaf-cutter ants and fungi?

Leaf-cutter ants harvest leaves to provide nutrition to fungal gardens in their nests.

How do some Acacia plants interact with ants?

They provide nourishment to ants that protect them from predators and competitors.

What is the impact of global climate change on food quality?

Nutritional quality of wild and crop plants has declined, possibly due to insufficient nutrient uptake.

What role do dead plants play in soil ecosystems?

They provide energy needed by soil-dwelling microorganisms.

What is the role of nitrogen-fixing bacteria in plants?

They convert atmospheric nitrogen (N2) into ammonia (NH3), which can be used by plants.

How do ammonifying bacteria contribute to nitrogen availability?

They break down dead organic compounds and release ammonium (NH4+).

What is nitrogen fixation?

The conversion of nitrogen from N2 to NH3, making it available for plant use.

What type of bacteria forms symbiotic relationships with legumes?

Nitrogen-fixing Rhizobium bacteria.

What are root nodules?

Swellings along a legume's roots that contain Rhizobium bacteria.

What form do Rhizobium bacteria take inside root nodules?

They assume a form called bacteroids, contained within vesicles formed by the root cell.

What benefits do plants and Rhizobium bacteria gain from their symbiotic relationship?

Plants obtain fixed nitrogen, while Rhizobium receives sugars and an anaerobic environment.

What is the significance of crop rotation involving legumes?

It restores the concentration of fixed nitrogen in the soil by alternating nonlegumes and legumes.

What are mycorrhizae?

Mutualistic associations between fungi and plant roots that enhance nutrient uptake.

How do mycorrhizal fungi benefit host plants?

They increase surface area for water uptake and supply mineral nutrients from the soil.

What are the two major types of mycorrhizae?

Ectomycorrhizae and arbuscular mycorrhizae.

How do ectomycorrhizae differ from arbuscular mycorrhizae?

Ectomycorrhizae form a sheath over roots and do not penetrate root cells, while arbuscular mycorrhizae penetrate root cells and form arbuscules.

What is the role of arbuscules in arbuscular mycorrhizae?

They are important sites for nutrient transfer between the fungus and the plant.

What is the ecological importance of mycorrhizae in agriculture?

Farmers often inoculate seeds with fungal spores to promote mycorrhizal formation, enhancing plant growth.

What are epiphytes?

Plants that grow on other plants and obtain water and minerals from rain without tapping into the host.

How do parasitic plants obtain nutrients?

They absorb sugars and minerals from their living host plants, some relying entirely on the host for sustenance.

What adaptations do carnivorous plants have for obtaining nitrogen?

They trap and digest insects and other small animals while being photosynthetic.

What is the significance of the mutualistic relationship between early land plants and fungi?

It allowed both to exploit terrestrial environments by providing essential nutrients and carbohydrates.

What happens to legumes after they are harvested in crop rotation?

They are often plowed under to decompose as 'green manure', enriching the soil with nitrogen.

What is the impact of invasive exotic plants on mycorrhizal fungi?

They can disrupt interactions between native plants and their mycorrhizal fungi, hindering growth.

What is the role of chemical signals in the formation of nitrogen-fixing root nodules?

They attract Rhizobium bacteria and facilitate the infection process leading to nodule development.

What are some examples of carnivorous plants?

Sundew, pitcher plants, and Venus flytraps.

What is the relationship between mycorrhizal fungi and soil pathogens?

Mycorrhizal fungi secrete antibiotics that help protect plants from soil pathogens.

In what percentage of plant species do arbuscular mycorrhizae occur?

About 85% of plant species, including most crops.

What is the role of the infection thread in nodule formation?

It forms as Rhizobium bacteria invade root hairs, leading to nodule development.