BI111 Week 9

Macronutrients and micronutrients in plant metabolism

• by weight, tissues of most plants are >90% water

• most plants nutrition come from photosynthesis

• smaller amounts of other nutrients come from soil or water

Nutrient deficiencies

• different experiments where they try to remove different elements

• soil determines how well plants grow

• nutrient deficiencies show

  • stunted growth , leaf color, dead spot, abnormal stems, chlorosis

Hydroponics

• method of growing plants without soil,

Root system

• make up 20-50% of total plant mass

• root grows as long as plants live

Mycorrhizae

• symbiotic associaticoosn between fungus and roots of plants

• plants encourage fungus and are good at bringing in nutrients

• plant gives fungus sugar for phosphorus

Apoplastic Pathway

• water doesn’t cross cell membrane

• substance moves between cels through cell wall and air spaces

Symplastic pathway

• water crosses membrane

• often uses plasmodesmata

• defuses through cytoplasm

Transmembrane pathway

• water crosses plasma membrane and perhaps tonoplasts

Casparian strip

• a band of waxy material found in the cell walls of endodermal cells in plant roots

• acts as a barrier that prevents water and dissolved substances from passing freely between adjacent cells in the root cortex

• helps regulate the uptake of water and nutrients in the plants

  • ensures potentially harmful substances are not allowed in the root system

Humus

• dark organic material that forms due to the decomposition of plant and animal matter in soil

• has a negative charge, which allows it to attract and retain positively charged ions, such as nutrients, making them available to plants.

What factors determine soil properties?

The relative proportions of sand, silt, and clay particles in the soil determine its texture, which impacts properties such as water retention, drainage, and nutrient availability.

What is soil development?

• Soil develops over time through the weathering of rocks and accumulation of organic matter, resulting in distinct layers or horizons with unique properties.

What are soil horizons?

• Soil horizons are visible layers within the soil profile, including the O horizon (organic layer), A horizon (topsoil), B horizon (subsoil), and C horizon (parent material).

How does soil texture affect plant growth?

• Soil texture impacts soil fertility, aeration, and the ability of plants to grow. Sandy soils drain quickly but hold fewer nutrients, while clay soils retain water and nutrients but can become compacted.

What are the characteristics of the O horizon?

• The O horizon, or organic layer, consists mainly of decomposing organic matter like leaves and plant debris.

What is found in the A horizon?

• The A horizon, or topsoil, is rich in organic matter, nutrients, and soil organisms, making it ideal for plant growth.

What is the role of the B horizon?

• The B horizon, or subsoil, accumulates minerals and nutrients leached from the upper layers, contributing to soil fertility.

What is the C horizon?

• The C horizon, or parent material, consists of partially weathered rock fragments and minerals, serving as the source of new soil formation.

What are some characteristics of soil in deciduous forests?

• Soil in deciduous forests tends to be acidic due to leaching in the B horizon. It contains organic material like fungi and decomposing plant matter, contributing to its acidity.

Describe the soil composition in rainforests

• Rainforest soil is typically nutrient-poor as most nutrients are held within the trees. It often contains high levels of iron and aluminum and is characterized by its poor fertility.

What are the soil conditions in coniferous forests?

• Coniferous forest soil is usually acidic and low in nutrients. The accumulation of needles and resin from coniferous trees makes the soil hard to break down, contributing to its poor fertility.

Explain the soil characteristics of grasslands

• Grassland soil is ideal for plant growth, with a rich A horizon containing abundant nutrients and organic matter. It typically has a neutral to slightly alkaline pH due to the presence of calcium carbonate.

What are the soil conditions in desert environments?

• Desert soils are often saline due to evaporation of water, leaving behind salt deposits. With minimal rainfall, desert soils lack organic matter and nutrients, making them inhospitable for plant growth.

What are taproots and where are they commonly found?

• Taproots are found in eudicot plants and are characterized by a single, dominant root that grows deep into the soil. They provide stability and allow plants to access water and nutrients from deeper soil layers

Describe the soil solution and ion exchange in plants.

• Humus in the soil has a negative charge, allowing it to retain positively charged ions. Through ion exchange, plants can release hydrogen ions to exchange with positively charged ions, facilitating nutrient uptake.

What are some nitrogen limitations in plants?

• Nitrogen is abundant in the air but can be limiting for plant growth. Plants have evolved various strategies, such as heterospory and the evolution of pollen and eggs, to ensure successful fertilization and reproductive success.

Explain the floral adaptations for successful reproduction.

• Flowers have various adaptations to facilitate pollination and reproduction, including floral morphology, dichogamy (sequential hermaphroditism), and herkogamy (physical separation of male and female reproductive structures). These adaptations enhance reproductive success and genetic diversity in plant populations.

What are some characteristics of pollen grains and ovules?

• Pollen grains are produced in large numbers in the anthers and consist of a multicellular male gametophyte. Ovules are located inside the carpel and contain the female gametophyte, which gives rise to the embryo sac upon fertilization.

Sepals (calyx)

• Sepals, also known as the calyx, initially protect the developing flower bud.

What is the main function of petals in a flower?

• Petals, also known as the corolla, serve as the main signaling mechanism of the plant, attracting pollinators such as bees, butterflies, and birds.

How do petals help in attracting pollinators?

• Petals, along with sepals, make up the perianth, which collectively helps attract pollinators through coloration and fragrance.

What is the structure of the stamen in a flower?

• The stamen, part of the androecium, is made up of three main parts: the anther, filament, and pollen.

What is the function of the anther in the stamen?

• The anther produces pollen, which contains the male gametes (sperm cells) used for fertilization.

What is the function of the carpel, also known as the pistil or gynoecium?

• The carpel contains the female reproductive structures of the flower, including the ovary, style, and stigma

What is the function of the stigma in the carpel?

• The stigma is the receptive surface where pollen lands during pollination, facilitating the transfer of pollen to the ovary for fertilization.

What is the function of the ovary in the carpel?

• The ovary is the enlarged basal portion of the carpel that houses the ovules, which contain the female gametophyte (egg cells). After fertilization, the ovary develops into a fruit containing seeds.