Life 103 Exam 2

1) Angiosperms:

a. Gametophytes vs. Sporophytes

The sporophytes is the diploid dominant, flowering body. The gametophyte is a microscopic, dependent haploid part of the plant. Male gametophytes are found in pollen grains. The female gametophyte or embryo sac develops within an ovule. 

b. Flowers and Fruits

Flowers are bisexual structures for sexual reproduction

Sepals enclose the flower bud

Petals attract pollinator

Carpals produce ovules. It consists of an ovary, style, and stigma. It is where pollen is received.

Stigma is the sticky part of a flower that receives pollen during pollination

Style is a tube-like structure that connects the stigma to the ovary

Ovary is the the part of a flower that contains ovules, which develop into seeds

Stamen is the male reproductive part of a flower that produces pollen. It consists of filament and an anther.

Filament is the thin stalk that supports the anther in a stamen

Anther is the part of a flower that produces pollen

Fruits are fleshy mature ovaries that protect the seeds and aid in dispersal

c. Seeds

As a seed matures, it dehydrates and enters a state of dormancy

The hypocotyl is the part of a seedling that connects the root to the stem, crucial for the plant's early development.

The radicle is the part of a seedling that develops into the primary root

Imbibition is the process of water uptake by a dry seed. Germination depends on this. 

2) Structure & Development:

a. Roots, Stems, Leaves

Plants are organized into a roots and shoots system

Roots anchor the plant, store carbs and absorb minerals and water

Taproot is a primary root that grows deep into the soil, providing stability and access to water and nutrients

Fibrous roots are a network of thin roots that spread out near the soil surface

Root hairs are extensions of root cells that increase the surface area for water and nutrient absorption

Apical bud the growing tip of a plant shoot that is responsible for the growth in length and the development of new leaves and flowers

The closer an axillary bud is to the active apical bud, the more inhibited it is

Leaves are the main photosynthetic organ of plants

Dermal tissue is the outer protective layer of the plant (epidermis and cuticle)

Vascular tissue allows for transport of water and minerals (xylem and phloem)

Xylem transports water and dissolved minerals from the roots to the rest of the plant

Phloem transports photosynthesis products from shoots to roots

Ground tissue is the tissue system in plants that fills the space between the epidermis and vascular tissue, involved in photosynthesis, storage, and support

b. Primary vs. Secondary Growth

Indeterminate growth is when a plant grows consistently throughout its life

Determinate growth is when plants stop growing at a certain size

Meristems are regions of undifferentiated cells in plants that are responsible for growth

Primary growth increases the length of plants

Secondary growth increases the width of plants

Lateral meristems add width to the plant

The vascular cambium is a type of lateral meristem that adds layers of vascular tissue called

secondary xylem (wood) and secondary phloem

The cork cambium  is a type of lateral meristem that replaces the epidermis with periderm,

which is thicker and tougher

In woody plants, primary growth and secondary growth occur simultaneously but in different locations

Primary growth in roots happens in zones of division, elongation, and differentiation/maturation

Plant cells elongate by filling a large central vacuole with water

In most eudicots, the vascular tissue consists of vascular bundles arranged in a ring

In most monocot stems, the vascular bundles are scattered throughout the ground tissue

c. Stomata

Stomata are pores in leaves that allow for gas exchange

Stomata open when the surrounding guard cells get an influx of K+ ions, which makes water go up its concentration gradient into the cell, causing the guard cells to swell and open.

3) Resource Acquisition:

There are two pathways through the plant, apoplast and symplast

The apoplast consists of everything external to the plasma membrane

The symplast consists of the cytosol of all the living cells in a plant, as well as the plasmodesmata

Water potential is the measure of the potential energy in water, influencing the direction of water movement in plants

Addition of solutes lowers water potential (more negative)

Water flows from regions of higher water potential to regions of lower water potential

Bulk flow is the movement of a fluid driven by pressure

Transpirational pull happens from cohesion of water and the evaporation of water from the leaves. It transports from roots to shoots

Root pressure is from a push of xylem sap

Negative pressure pulls water from the xylem into the leaf

Translocation is when the the products of photosynthesis are transported through

phloem

a. Root Hairs, Casparian Strip

The casparian strip is waxy and blocks the flow of water & solutes from the cortex to the vascular cylinder via the apoplast

b. Sources vs. Sinks

Sources are parts of the plant the produce sugar

Sinks are parts of the plant that consume the sugar made by the source

4) Soil & Nutrition:

Plants obtain most of their water and minerals from the

upper layers of soil called topsoil

Topsoil (A horizon) consists of mineral particles, living organisms, and humus (decaying organic material)

Carnivorous plants photosynthesize, but obtain nitrogen from killing and digesting insects

a. Overwatering

Causes root rot, where roots begin to decay due to lack of oxygen, leading to decreased nutrient uptake.

Washes away the needed anions

b. Cation Exchange

Cations adhere to the negatively charged soil particles to prevent them from leaching out due to groundwater

During cation exchange, cations are displaced from soil particles by other cations, particularly H+ secreted by the roots

Negatively charged ions (PO43- or NO3-) do not bind with soil particles and can be lost from

the soil by leaching

c. Roles of Important Nutrients

96% of a plant’s dry mass is from CO2 assimilated into carbohydrates during photosynthesis

Micronutrients are mostly enzyme cofactors

Plants can absorb nitrogen as either NO3– or NH4

Nitrogen fixation the process by which nitrogen in the atmosphere is converted into ammonia or related compounds in soil with the help of Rhizobium bacteria

Some legume have nodules full of Rhizobium bacteria, in a symbiotic relationship. The bacteria get sugar and the plant gets nitrogen. 

d. Other organisms in the topsoil (N-fixers, Mycorrhizae)

Mycorrhizae are mutualistic associations of fungi and roots. The fungus benefits from the plant's sugar, and the plant benefits as the fungus increases the surface area of the roots for better water absorption. 

5) Angiosperm Reproduction:

a. Double Fertilization

Where one sperm fertilizes the egg to form the zygote, while another sperm fuses with two polar nuclei to form a triploid endosperm.

The endosperm provides nutrients to the developing embryo. 

b. Asexual vs. Sexual Reproduction

Asexual reproduction results in a clone of genetically identical organisms. It can be beneficial to plants in stable environments. 

c. Flowers and Seeds

Dioecious flowers have male and female parts of different plants, and require both for fertilization. 

d. Angiosperm life cycle