Bio 200 Exam 2

Taproot

large, central and dominant main root that grows straight down the soil

Lateral Root

small branches that extend horizontally or diagonally to increase volume

Roots

show phenotypic plasticity, with form that changes with environmental conditions. Environment can determine type and depth of this system.

Sun Leaves

have relatively small surface area, reducing water loss in areas of the body where light is abundant

Shade Leaves

relatively large and broad, providing a high surface area to maximize photon absorption

Ground Tissue

stem cells, bulk of body for many plants, help stiffen non-woody plants. Parenchyma = unspecialized cells with thin primary walls, with the function of photosynthesis, secretions, storage, and cabohydrates.

Vascular Tissue

consists of xylem and phloem, that moves water, minerals, and food throughout roots, stems, and leaves while providing structural support.

Xylem

(tracheids and vessel elements) serves purpose once dead, conductive cells with thick cell walls arranged end to end that form hollow passages. Function to transport water and minerals from roots to leaves & support.

Phloem

conductive cells living at maturity. Sieve-tube elements = lack nuclei, connected by plasmodesmata. Long, thin cells with perforated ends called sieve plates. Companion cells = maintain the cytoplasm and plasma membrane of sieve-tube elements.

Dermal Tissue

outermost cells on a leaf, which secrete a waxy cuticle/protective substances

Aquaporins

greatly increases the rate at which water diffuses through passive transport.

Apoplast

water travels between cell walls

Symplast

water travels between membrane to membrane

Cavitation

the sudden formation of a gas-filled space or air bubble (embolism) inside a plant's water-conducting vessels or tracheids. This breaks the continuous column of water being pulled up from the roots to the leaves

Guard Cell

creates electrochemical gradient, water follows by osmosis, cells swell and stomata opens. Controls rate of evaporation, which controls upwards force, controlling cavitation.

Photosynthate

Solution of sucrose/fructose

Translocation (Pressure Flow Hypothesis)

the movement of dissolved organic solutes (such as sucrose and amino acids) en masse through the phloem sieve tubes from a source (where they are produced or released) to a sink (where they are used or stored)

Phototropism

directional growth of a plant or fungus in response to a light source. Positive = toward light, negative = away from light.

PHOT1 / phototropin 1

more PHOT1 is phosporylated in response to blue light than in darkness.

Red Light

involving phytochrome (which transduces the signal), this wavelength is a cue to germinate for seedlings because it indicates that they are in full sun.

Far Red Light

involving phosphorylated phytochrome, this wavelength is a cue to inhibit germination for seedlings because it indicates that they are in shade.

ABA/Abscisic Acid

binding of this causes an intracellular release of calcium, which inhibits the ATPases and creates an electrochemical gradient that sends Cl- and other anions out of the cell. K+ channels open and K+ leaves the cell. Water follows, and the cells shrink, causing the stomata to close.

Glycophytes

salt-sensitive plants, unable to grow in saline soils

Halophytes

salt-tolerant plants, able to grow in saline soils. Can excrete excess, absorb + store excess, and regulate amount roots absorb.

Essential Nutrient

required for both normal growth and reproduction and for a specific structure or metabolic function. Oxygen, carbon, and hydrogen are the big 3.

Macronutrients

building blocks of nucleic acids, proteins, carbohydrates, phospholipids, and other key molecules required in relatively large quantities.

Limiting Nutrients

macronutrients that commonly act as limits on plant growth (nitrogen, potassium, phosphate).

Micronutrients

required in very small quantities, function as cofactors for specific enzymes (chlorine, iron, manganese, zinc, boron, etc).

Texture

refers to the proportions of different-sized particles present in soil. Affects ability of roots to penetrate the soil and the ability of the soil to hold water, dictate availability of oxygen.

Anions

dissolve in soil water due to interacting with h-bonding, trade-off: available to plants for absorption, but easily washed out of soil.

Cations

bind to organic matter in organic acids, and surface of clay. Retained in soils, not as available to plants.

Cation Exchange

occurs when protons or other cations in soil water bind to negative charges on soil particles. Found in root hair cells, which establish a proton gradient in the soil pre-water. For these, they enter through CHANNELS.

Anions

for negatively charged materials, they enter root hairs via COTRANSPORTER.

Mycorrhizal Fungi

80% of plant species have some kind of association, wrapped around root system increases surface area—> increased capacity for water and nutrient uptake, and in turn plant provides sugars back.

Nitrogenase

found in nitrogen-fixing bacteria, inactive in the presence of oxygen

Rhizobia

infects a root cell via “infection threat” through the plant’s own extended root hair, where it goes inside the vacuole of a host cell. This then transforms into a “bacteroid,” with a loss of cell wall and motility and the induction of N2 fixation biochemical pathway. The plant forms a root nodule, and the plant makes leghemoglobin to pack it into vacuoles w/ the bacteroids to keep away the oxygen, continuing nitrogen fixation.

Osmotic Pressure

higher the force, higher the osmotic pressure

Osmoconformer

doesn’t lose or gain a lot of water from the environment. Match their internal osmotic pressure (solute concentration) to the osmolarity of their surroundings.

Osmoregulator

organisms that actively control and maintain a constant internal salt and water balance (osmotic pressure), independent of the surroundings

Salt Glands

packed with chloride cells, really good at transporting chloride

Process of Chloride Cells

Na⁺ and Cl⁻ enter the transport pathway, (Na⁺/K⁺-ATPase) Uses ATP to pump Na⁺ out of the cell and K⁺ into it, Na⁺-K⁺-2Cl⁻ cotransporter (NKCC) Uses the ion gradients to bring Na⁺, K⁺, and 2 Cl⁻ into the cell, (K⁺ channels) Allow K⁺ recycling to maintain suitable ion gradients, (Cl⁻ channels) Cl⁻ exits the cell into the seawater-facing duct or surface. Na⁺ follows mainly through a paracellular pathway, helping produce net NaCl secretion.