Endterm Flashcards

Dessication

Excessive water loss; drying out

Desiccation tolerance

A suite of biochemical traits that allow cells to survive extreme dehydration by minimizing damage to membranes and macromolecules

Shoot

The collective name for the leaves, stems, and reproductive organs; the major above ground organ systems of vascular plants

Epidermis

The outermost layer of cells in multicellular organisms such as plants and animals

Vascular Tissue

A plant tissue that extends from leaves to roots and allows water and nutrients to move by bulk flow

Ground Tissue

Everything that is neither epidermis nor vascular tissues

Parenchyma

Thin-walled cells that perform many metabolic functions, including photosynthesis and storage of nutrients, carbohydrates, and water

Mesophyll

The photosynthetic cells that make up the tissue between the upper and lower epidermis of plant leaves

Vein

A vascular conduit within the leaf; in animals, a large, low pressure vessel that returns blood to the heart

Transpiration

The loss of water from leaves

Guard Cell

One of two cells surrounding the central pore of a stoma and that regulates the opening and closing of this pore

Crassulacean Acid Metabolism (CAM)

A process in plants that helps balance carbon dioxide gain and water loss by opening stomata and capturing carbon dioxide into 4-carbon organic acids at night, when transpiration rates are low, and then using it to supply the Calvin cycle during the day while stomata remain closed

C4 Plant

A plant in which carbon dioxide is incorporated into 4-carbon organic acids in mesophyll cells that are then used to supply the Calvin cycle in bundle-sheath cells; results in the suppression of photorespiration

C3 Plant

A plant in which carbon dioxide is first incorporated into a 3-carbon molecule during photosynthesis. This contrasts with a plant, in which carbon dioxide is first incorporated into a 4-carbon molecule

Vessel Element

An individual cell that is part of a xylem vessel for water transport in plants

Pit

In vascular plants, porous regions that allow water to flow from one xylem conduit to another, but prevent air from spreading

Water Potential

The free energy of water in which water moves from an area of high water potential to an area of low water potential

Cavitation

The abrupt replacement of liquid water in a xylem conduit by water vapor, which prevents water from being pulled through the xylem by transpiration

Source

Regions that produce or store carbohydrates

Sink

Any portion of the plant that needs carbohydrates to fuel growth and respiration; examples are roots, young leaves, and developing fruits

Companion Cell

In angiosperms, a cell associated with sieve tubes that carries out cellular functions such as protein synthesis.

Phloem Sap

The sugar-rich solution in plants that flows through both the lumen of the sieve tubes and the sieve plate pores

Sieve Tube

In angiosperm phloem, a multicellular unit composed of sieve elements that are connected end to end, through which phloem transport takes place

Sieve Plate

A modified end wall with large pores that links sieve elements

Rhizosphere

The soil layer that surrounds actively growing roots

Root Hairs

A slender outgrowth produced by epidermal cells that greatly increases the surface area of the root.

Endodermis

A layer of cells that acts as a gatekeeper controlling which nutrients move into the xylem

Casparian Strip

A thin band of hydrophobic material that prevents water and any dissolved materials from moving through the cell wall

Mycorrhizae

Symbioses between roots and fungi: the plant provides carbohydrates produced by photosynthesis, and the fungus provides nutrients it has obtained from the soil

Ectomycorrhizae

One of the two main types of mycorrhizae; ectomycorrhizae produce a thick sheath of fungal cells (hyphae) that surround the root tip, as well as hyphae that grow between, but do not penetrate, cells in the interior of the root

Endomycorrhizae

One of the two main types of mycorrhizae; endomycorrhizal hyphae penetrate into root cells, where they produce highly branched structures (arbuscules) that provide a large surface area for nutrient exchange

Nitrogen Fixation

The process by which some Bacteria and Archaea convert nitrogen gas into ammonia, a form biologically useful to primary producers

Root Nodule

A structure, formed by dividing root cells, in which nitrogen-fixing bacteria live

Shoot apical meristem

A group of totipotent cells at the tip of a stem or branch that gives rise to new shoot tissues in plants.

Axillary bud

A meristem that forms at the junction between a leaf and the stem

Node

A point along the stem where one or more leaves are attached and which has one or more axillary buds

Internode

The section of stem between successive nodes

Meristem identity gene

A gene that contributes to meristem stability and function

Petiole

A structure that connects a leaf to its stem

Bud scale

Small modified leaves that protect shoot apical meristems from desiccation and damage due to cold

Primordia

An organ in its earliest stage of development; in plants, leaf primordia form near the tips of shoot apical meristems and develop into leaves

Procambial cell

A plant cell that retains the capacity for cell division and gives rise to both xylem and phloem

Cortex

The tissue between the epidermis and the vascular bundles

Pith

In a stem, the region inside the ring of vascular bundles

Root apical meristem

A group of totipotent cells near the tip of a root that is the source of new root cells

Root cap

A structure that covers and protects the root apical meristem as it grows through the soil

Pericycle

In roots, a single layer of cells just to the inside of the endodermis from which new root apical meristems are formed, allowing roots to branch

Lateral meristem

The source of new cells that allows plants to grow in diameter

Vascular cambium

Lateral meristem that is the source of new xylem and phloem

Cork cambium

Lateral meristem that renews and maintains an outer layer that protects the stem against herbivores, mechanical damage, desiccation, and fire

Secondary xylem

New xylem cells produced by vascular cambium, which are located to the inside of the vascular cambium

Secondary phloem

New phloem cells produced by the vascular cambium, which are located to the outside of the vascular cambium

Sapwood

In long-lived trees, the layer adjacent to the vascular cambium that contains the functional xylem

Heartwood

The center of the stem in long-lived trees, which does not conduct water

Growth ring

One of the many rings apparent in the cross section of the trunk of a tree, produced by decreases in the size of secondary xylem cells at the end of the growing season, that make it possible to determine the tree's age

Suberin

In plants, a waxy compound found in the walls of cork cells that protects against mechanical damage, the entry of pathogens, and water loss

Lenticel

Small regions where the outer bark cells are less tightly packed

Auxin

A plant hormone that plays a major role in plant development through the establishment of concentration gradients that guide patterns of cell growth and differentiation

Polar transport

The coordinated movement of auxin across many cells

Gibberellin

A plant hormone that stimulates the elongation of stems

Cytokinin

A plant hormone that stimulates cell division and delays leaf senescence

Apical dominance

The suppression of growth of axillary buds by the shoot apical meristem, typically by the action of auxin hormone

Strigolactone

A plant hormone that inhibits the outgrowth of axillary buds

Tropism

The bending or turning of an organism in response to an external signal such as light or gravity

Phototropic

When plants bend toward the light

Gravitropic

When plants grow upward against the force of gravity

Statolith

Specialized gravity-sensing cells in the root cap contain large starch-filled organelles

Phytochrome

A photoreceptor that switches back and forth between two stable forms, active and inactive, depending on its exposure to red and far-red light

Abscisic acid

A plant hormone that triggers stomatal closure, stimulates root elongation, and maintains seed dormancy

Thigmotropism

Developmental response to a mechanical stimulus arising from physical contact

Photoperiodism

The effect of the photoperiod, or day length, on physiological or developmental processes; in plants, the effect of day length on flowering

Short-day plan

A plant that flowers only when the day length is less than a critical value

Long-day plant

A plant that flowers only when the duration of the light period exceeds a critical value

Day-neutral plant

A plant that flowers independently of any change in day length

Vernalization

A prolonged period of exposure to cold temperatures necessary to induce flowering in some plants

Host plant

Species that can be infected by a particular pathogen

Biotrophic pathogen

A plant pathogen that obtains resources from living cells

Necrotrophic pathogen

A plant pathogen that kills cells before drawing resources from them

Virulent

Describes a microbe or virus that causes disease or significant damage to the host

Avirulent

Describes a microbe or virus that lacks the ability to cause disease or significant damage to the host

Basal resistance

A component of the plant immune system that recognizes molecules produced by broad classes of pathogens; contrast with specific resistance

Specific resistance

A component of the plant immune system that recognizes proteins produced by specific pathogens; contrast with basal resistance

Avr protein

An avirulence protein produced by a plant pathogen that blocks the host plant's immune response and is detected by resistance (R) proteins

R protein

Any one of a group of resistance proteins in plant cells, each expressed by a different R gene, that functions as part of the plant's immune system by detecting the presence of a specific pathogen-derived Avr protein

R gene

Any one of a group of genes that expresses an R (resistance) protein in plants

Hypersensitive response

A type of plant defense against infection in which uninfected cells surrounding the site of infection rapidly produce large numbers of reactive oxygen species, triggering cell wall reinforcement and causing the cells to die, thus creating a barrier of dead tissue

Systemic acquired resistance (SAR)

The ability of a plant to resist future infections, occurring in response to a wide range of pathogens

Small interfering RNA (siRNA)

A type of small double-stranded regulatory RNA that becomes part of a complex able to cleave and destroy single-stranded RNA with a complementary sequence

Ti plasmid

A small circular DNA molecule in virulent strains of Agrobacterium tumefaciens containing genes that can be integrated into the host cell's genome, as well as the genes needed to make this transfer

Trichome

Hairlike outgrowths on the surfaces of leaves and stems; may provide protection from herbivores and excess sunlight

Latex

A white sticky liquid produced in some plants

Alkaloid

Nitrogen bearing compounds that damage the nervous system of animals

Terpene

Any one of a group of compounds that do not contain nitrogen and are produced by some plants as a defensive mechanism

Tannin

Any one of a group of phenols found widely in plant tissues that bind with proteins and reduce their digestibility

Protease inhibitor

A molecule that blocks the action of enzymes that break down proteins

Extrafloral nectar

A nectar-producing gland not associated with flowers, often located on leaves

Constitutive Defense

Defenses that are always present

Inducible defense

A defense that is activated only when the plant senses the threat

Integrated pest Management (IPM)

A method of pest control that monitors pest populations, encourages predator populations, applies mechanical and targeted chemical control when pest populations reach levels that cause economic losses, and uses nonspecific pesticides only as a last resort

Porifera

Sponges; an animal phylum characterized by few cell types, no well-defined tissues, and no clearly defined plane of symmetry