Soils, Nutrients, Photosynthesis, and Flower Reproduction in Plants

What determines many aspects of a plant's life?

Soil composition

What are essential elements for plants?

Necessary for plant growth and reproduction; without them, plants cannot complete their life cycles.

What are beneficial elements?

Elements that might not be necessary but help the plant thrive.

What are macronutrients?

Nutrients required in relatively large quantities (usually >0.1% of dry biomass).

What are micronutrients?

Nutrients required in small quantities (usually < 0.01% of dry biomass).

How do plants absorb most mineral nutrients?

As ions from the soil.

What are anions?

Negatively charged ions, e.g., Phosphorous (H2PO4-), Nitrogen (NH4+), and Chloride (Cl-).

What are cations?

Positively charged ions, e.g., Calcium (Ca2+), Magnesium (Mg2+), and Iron (Fe3+ or Fe2+).

What is cation exchange?

The process where plants release H+ to free cations from soil particles.

What role do proton pumps play in nutrient absorption?

They use ATP to pump H+ outside of the cell, generating a potential difference that pulls cations into the cell.

What is the challenge of absorbing anions?

The potential difference keeps anions out, but H+ ions can form complexes with anions to facilitate their entry.

What are common causes of eutrophication?

Nitrates and phosphates.

How can minerals be replenished in the rhizosphere?

Through bulk water flow, diffusion, and root growth.

What is the role of carbon in plants?

Essential for photosynthesis and forming organic molecules such as cellulose.

What is the importance of nitrogen for plants?

Part of proteins, nucleic acids, and chlorophyll.

What are symptoms of nutrient deficiency in plants?

Stunted growth, chlorosis (yellowing of leaves), and necrosis (tissue death).

What is the Haber-Bosch process?

An industrial process for producing ammonia, key for artificial fertilizers.

What are the four components of soil?

Organic matter, inorganic mineral matter, water, and air.

What is humus?

Partially decayed organic matter that increases nutrient content, water retention, and aeration in soil.

What are the three types of soil particles?

Sand (100 μm to 2 mm), Silt (2 to 100 μm), Clay (< 2 μm).

What is soil texture?

Based on the percentages of sand, silt, and clay.

What are organic soils?

Soils formed from sedimentation, containing more than 30% organic matter.

What are mineral soils?

Soils formed from the weathering of rocks, usually containing less than 30% organic matter.

What are soil horizons?

Different layers in the soil profile, including O, A, B, and C horizons.

What happens during soil formation?

Dissolving elements from rock occurs when rain dissolves CO2 and becomes slightly acidic.

What is the difference between young and mature soils?

Young soils are rich in minerals but may have toxic concentrations, while mature soils have lower nutrient concentrations but better cation binding.

What pH range is optimal for most plants?

5.5 to 6.5.

How does soil pH affect nutrient availability?

Acidic conditions increase proton concentration, freeing essential cations and influencing microbial communities.

What are the two main importance of photosynthesis?

Liberation of oxygen for aerobic respiration and transformation of low energy compounds (CO2 and water) into high-energy compounds (sugars).

Who showed that plants do not obtain their biomass from the soil?

Joannes van Helmont in the early 1600s.

What did Joseph Priestly demonstrate in 1772?

That plants could restore air.

What did Jan Ingehousz observe in 1796?

That carbon was fixed by the plant.

What is the general equation for photosynthesis as concluded by Cornelis van Niel?

The oxygen released by plants comes from water (not CO2).

What did T.W. Engelmann's experiment in the 1880s reveal about light and photosynthesis?

Red and blue light supply most of the energy for photosynthesis.

What are the two general parts of photosynthesis?

Light-dependent reactions and light-independent reactions.

What occurs during the light-dependent reactions of photosynthesis?

Light excites pigments, and energy is used to form ATP and NADPH.

What is the Calvin cycle?

The light-independent reactions that fix carbon into sugars.

What are the two main structural parts of chloroplasts?

Thylakoids and stroma.

What is the role of thylakoids in chloroplasts?

They are the site of the light-dependent reactions.

What are the two types of chlorophyll pigments?

Chlorophyll a and chlorophyll b.

What is the function of carotenoids in plants?

They absorb UV, violet, and blue light and may play a protective role.

What happens when light excites photosystem I?

An electron in P700 moves to a higher state and is transferred to NADP+ to produce NADPH.

What is photolysis in the context of photosynthesis?

The process where oxidized P680+ splits water to recover electrons.

How is ATP synthesized during photosynthesis?

H+ ions move back to the stroma via ATP synthase, catalyzing ATP formation.

What is the role of Rubisco in the Calvin cycle?

It catalyzes the combination of CO2 with RuBP to produce phosphoglyceric acid (PGA).

What is photorespiration?

A process that occurs when CO2 concentrations are low, leading Rubisco to add O2 to RuBP.

What is the C4 pathway in photosynthesis?

A pathway that first combines CO2 with PEP to form a four-carbon compound, increasing CO2 concentration.

What is CAM photosynthesis?

A modification of the C4 pathway that allows stomata to open at night to absorb CO2.

What is the first product formed in the C3 pathway?

Phosphoglyceric acid (PGA).

What happens to PGAL in the Calvin cycle?

Some PGAL is used to reform RuBP, while others can be converted to DHAP or form carbohydrates.

What is the significance of the light intensity on the rate of photosynthesis?

Under sufficient light and CO2, the photosynthetic rate increases with temperature; at low light, temperature has little effect.

What is the role of the stroma in chloroplasts?

It is the site of light-independent reactions and contains DNA, ribosomes, and enzymes.

What are the two reaction centers in the photosystems?

P700 in photosystem I and P680 in photosystem II.

What is resonance in the context of pigment absorption?

The process where energy from an absorbed photon is transferred to adjacent pigments until it reaches the reaction center.

What is the first step in the sexual reproductive cycle of flowers?

Production of special reproductive cells following meiosis.

What are the key steps in the sexual reproduction of flowers?

1. Production of reproductive cells, 2. Pollination, 3. Fertilization, 4. Seed/fruit development, 5. Dispersal, 6. Germination.

What is the role of vivid colors and scents in flowers?

To attract pollinators and direct them towards the plant's gametes.

What are the four whorls of a typical flower?

1. Sepals, 2. Petals, 3. Stamens, 4. Carpels.

What is the calyx in flower morphology?

The collective term for sepals.

What is the corolla in flower morphology?

The collective term for petals.

What is the perianth?

The non-reproductive part of the plant, consisting of the calyx and corolla.

What is the androecium?

The whorl grouping the stamens (male organs).

What are the two parts of a stamen?

Anther and filament.

What is the gynoecium?

The whorl grouping the carpels (female organs).

What are the three parts of a carpel?

Ovary, style, and stigma.

What is the function of the pollen grain?

To produce sperm cells for fertilization.

What happens during double fertilization?

One sperm cell fuses with the egg cell to form a zygote, and the other fuses with two polar nuclei to form endosperm.

What is the ABC model in flower development?

A model explaining the production of floral organs based on the expression of three genes.

What distinguishes complete flowers from incomplete flowers?

Complete flowers have all four whorls, while incomplete flowers lack at least one whorl.

What are unisexual flowers?

Flowers that are either staminate (stamen bearing) or pistillate (pistil bearing).

What is the difference between self-pollination and cross-pollination?

Self-pollination occurs within the same flower or plant, while cross-pollination involves pollen from different plants.

What adaptations do wind-pollinated plants have?

They are usually small, colorless, odorless, and lack nectar, with reduced perianths to increase exposure of anthers and stigmas.

What is the role of nectaries in flowers?

To secrete nectar, a sugary reward for pollinators.

What is placentation in flower anatomy?

The distribution form of the placenta, where ovules are attached in the ovary.

What is the micropyle in the ovule?

A small opening left by the integuments for fertilization.

What is the female gametophyte in flowering plants?

The embryo sac.

What are the three parts of the embryo sac?

The egg apparatus, central cell, and antipodal cells.

What is the function of the stigma in the gynoecium?

To receive pollen during pollination.

What is the significance of directed pollination?

It has allowed angiosperms to become widespread by effectively attracting specific pollinators.

What happens to the majority of megaspores formed during ovule maturation?

Three megaspores disintegrate, leaving one to develop into the embryo sac.

What is the role of the ovary in the gynoecium?

To contain ovules and develop into fruit after fertilization.