Plant Biology

• Plant growth is low in arid regions because stomatal closure prevents CO2 uptake.
• Water potential decreases (becomes more negative) when stomata close during the night.
• Phytochrome responds to red light.
• A plant apoplast includes all spaces outside the living cell membrane, such as the cell wall and vessels.
• Auxins promote root growth.
• The endodermis is mainly responsible for the selection of nutrient uptake in roots.
• Hygroscopic movement in plants is reversible.
• Transport in the phloem is passive.
• The Calvin cycle is part of photosynthesis.
• The dark reaction takes place in the stroma.
• Cotyledons are mainly eaten in beans.
• Chamaeophytes are dwarf shrubs.
• The endodermis is found in roots.
• Therophytes are plants surviving as seeds.
• Parenchyma cells are/serve for isodiametric.
• Collenchyma cells do not belong to the xylem.
• Casparian strips are found in the endodermis.
• Lilac (Flieder) is a phanaerophyte.
• Lignin is a compound that incrusts cell walls.
• Companion cells are next to sieve tubes.
• Suberin makes cork water-impermeable.
• Cryptophytes are tall woody plants.
• Helophytes are plants whose surviving buds are underwater.
• Potatoes are tubers.
• Parenchyma tissue can become meristematic again.
• Lenticells serve for gas exchange.
• A protein is a polymer composed of many amino acids.
• Starch is the most common reserve substance of plants.
• Plants produce oxygen (O2) during the light-dependent reaction.
• In photosynthesis, oxygen comes from water molecules.
• The production of RNA as a copy of a DNA strand is called transcription.
• Thylakoids are membranes.
• Chromosomes are composed of DNA and protein.
• Nucleotides are found in DNA.
• Rubisco is the enzyme that binds CO2.
• Cellobiose is a disaccharide composed of two glucose units.
• When chlorophyll molecules give off an electron, it is replaced with an electron from H2O.
• A biomembrane always includes phospholipids.
• The membrane surrounding the vacuole is the tonoplast.
• NaCl concentration can be reduced inside the cell via active transport.
• Ribosomes are not surrounded by a membrane.
• Starch is stored in the amyloplast.
• The endoplasmatic reticulum (ER) contains no DNA.
• Mimosa shows seismonastic movement.
• Collenchyma cells stay alive when mature.

Open Questions

• The main function of roots is anchoring the plant in the soil and water + mineral nutrient uptake.
• Roots don't photosynthesize, and are under the ground.
• A rhizome is a subterranean thick shoot that serves as a storage and hibernating organ, with leaves that are present but strongly reduced.
• In shoots, the apical meristem is protected in buds by leaves, while in roots, it is protected by the root cap.
• The dead bark in trees is formed through secondary thickness growth, composed of one or several cork layers and other tissues in between.
• Examples of root metamorphosis include storage roots like sweet potato and carrot, root tendrils like vanilla, and root thorns like palm tree.
• Examples of shoot metamorphosis include tubers like potatoes, bulbs like onions, and tendrils like vines.
• Examples of leaf metamorphosis include bracts, cotyledons, sun leaves, and shade leaves.
• Three types of cells:
  • Vascular tissues: For water and nutrient transport (in xylem + phloem).
  • Dermal tissues: Primary (epidermis, rhizodermis), secondary (periderm).
  • Ground tissues: Mainly for stabilization of the plant.
• The function of respiratory roots is to supply below-ground roots with oxygen, especially in poor soils, and are found in many mangroves.
• The function of the living bark is to protect against water loss, extreme temperature, and mechanical damage.
• Both vessels and tracheids are dead, thick-walled, and lignified.
  • Tracheids: Elongated single cells, connected via pits, for water transport and stabilization which has a speed of transport which is ~ 0.4 mm/s.
  • Vessels: Long tubers, individual cells, used only for water transport which has a speed of transport: 15 - max. 40 mm/s
• The border pits in conifer wood function as 'check valves'.
  • When embolism occurs, the thickened central membrane is sucked to one side, closing a large pore to block the spread of emboli.
• Vascular bundles: In roots, they are in one radial bundle; in shoots, they are collateral.
  • Phanerophytes: Woody, perennial, >30 cm above ground, trees and shrubs
  • Geophytes: Plants surviving with storage organs
  • Therophytes: Annuals, plants that survive as seeds
• Vascular tissue forms the xylem in angiosperms.
• The pericycle gives rise to the periderm.
• The epidermis has no intercellular spaces (except stomata!), no chloroplasts, and is a single layer of cells with thickened outer walls.
• The rhizodermis has no stomata or cuticle and bears no leaves.
• Meristems are found in embryonic tissues.
• Intercellular spaces are small or large spaces between cells, mostly filled with gas or sometimes filled with a plant product.