BIOL 1010 | Chapter 32 Definitions

casparian strip

waxy barrier in endodermal cell walls that blocks unregulated flow of water/solutes and forces them to cross a selective plasma membrane before entering xylem

xylem sap

solution of water + inorganic nutrients that flows from plants roots through xylem vessels to leaves + supplies essential material for photosynthesis

transpiration

process where water evaporates from surfaces of leaves + creates negative pressure that pulls water up from roots through xylem

cohesion

property of water molecules to stick to each other through hydrogen bonds which allows formation of continuous water in xylem

adhesion

tendency of water molecules to cling to walls of xylem vessels which helps counteract gravity + assist with upward flow of water

sieve-tube elements

living phloem cells arranged end-to-end into long tubes that conduct sugars through plant

sieve plates

perforated end walls of sieve-tube elements that allow phloem sap to flow between cells

phloem sap

sugary liquid composed of SUCROSE + inorganic ions, amino acids and hormones → transported through phloem

sugar source

plant organ that produces/releases sugar (photosynthesis/starch breakdown) → usually LEAVES

sugar sink

plant organ that consumes/stores sugars (roots, buds, stems, fruits, tubers, bulbs)

pressure flow mechanism

sugar loading at source increases phloem solute concentration => water IN by osmosis to RAISE pressure

sugar UNloading at SINK => lowers solute + pressure → drives phloem sap from source to sink

autotroph

organism makes its own organic compounds from INORGANIC sources 

essential element

nutrient that a plant must obtain from its environment to complete its life cycle

macronutrients

nutrients that plants require in large amounts (carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorous, calcium, potassium, magnesium)

micronutrients

nutrients that plants require in small amounts (chlorine, iron, manganese, boron, zinc, copper, nickel, sodium)

fertilizers

substances added to soil to supply essential nutrients and promote plant growth (usually for nitrogen, phosphorous and potassium)

compost

biologically derived soil-like mixture of decomposed organic matter

horizons

layers of soil with different composition, structure and biological activity

topsoil

uppermost soil layer (A horizon) rich in organic matter → primary medium for plant root growth

humus

partially decomposed organic material in soil that improves soil structure

cation exchange

root hairs release hydrogen ions into soil → displaces positive charged ions from soil particles so they can be absorbed by plant

irrigation

artificial application of water to soil to assist in growth of crops (make sure they get enough water)

erosion

process where soil is worn away/removed by wind/water → leads to loss of fertile topsoil

organic farming

agricultural practices that maintain soil quality and ecosystem health through natural methods such as crop rotation, cover crops, composting, and minimal or no synthetic fertilizers or pesticides, avoiding genetically modified organisms

sustainable agriculture

a farming system that uses environmentally safe practices designed to maintain soil, water, and genetic resources over the long term, allowing agriculture to be productive

GMO (genetically modified organisms)

organisms whose genetic material has been altered using biotechnology to introduce specific traits

herbicides

chemicals used to kill or inhibit the growth of unwanted plants (weeds) that compete with crops for resources

nitrogen fixation

certain bacteria convert atmospheric nitrogen gas (N₂), which plants cannot use, into ammonia (NH₃), which can then be transformed into ammonium (NH₄⁺) and made available to plants

mutualistic relationship

a type of symbiotic relationship in which both organisms benefit from the association, such as plants and fungi or plants and nitrogen-fixing bacteria.

mycorrhiza

a mutually beneficial association between plant roots and fungi, in which the fungus increases water and mineral absorption for the plant while receiving sugars and other organic compounds in return

nodules

specialized swellings on the roots of certain plants, where nitrogen-fixing bacteria (Rhizobium) live and convert atmospheric nitrogen into a form usable by the plant

epiphyte

a plant that grows on another plant for physical support but does not extract nutrients from its host; it produces its own food via photosynthesis and absorbs water and minerals from rain or debris

parasite

plant that obtains water, sugars, and minerals from a living host, often at the host’s expense, using specialized structures to tap into the host’s vascular tissue

carnivore

plant that captures and digests animals, usually insects, to supplement its nutrient intake in nutrient-poor soils