AGRI 31 2ND LEC EXAM

Photorespiration

• rubisco carboxylates and oxygenates

• oxidation of RuBP yields 1 molecule of 3-PGA and 1 molecule of phosphoglycolate

• loses 25% of the carbon it takes from the calvin cycle

• wasteful process

Kranzy anatomy

vascular bundles are surrounded by a sheath of chloroplast-rich parenchyma cells (vascular bundle sheath)

C4 plants

• first incorporate carbon dioxide into four-carbon compounds befor ethe calvin cycle

• photosynthetic reactions occur in separate cells (mesophyll and bundle sheath cells)

CAM pathway

• succulent plants

• exhibited by plants that are growing in very arid, dry, and hot environmnets

• light and dark reactions are separated in time

respiration

enzyme-catalyzed reaction involving the transformation of organic substrates into carbon dioxide and water, accompanied by the release of energy

glycolysis

• first step in dark respiration, occurs in cytoplasm

• yields 2 molecules of pyruvic acid (3-C)

mitchondrial matrix

• site of krebs cycle

• synonymous to tricarboxylic acid cycle and citric acid

krebs cycle

generates 6 NADH and 2FADH2, and yields 2 ATP via substrate-level phosphorylation

electron transport system

• final stage of dark respiration

• occurs in the inner mitochondrial membrane

• ATP is generated via oxidative phosphorylation

growth respiration

cost of converting the immediate products of photosynthesis into plant material

maintenance respiration

CO2 resulting from protein breakdown plus the CO2 produced in respiratory processes that provide energy for maintenance processes

transpiration

loss of water from plants in the form of water vapor

guttation

water droplets are secreted through he hydathodes because of very high root pressure

cuticular transpiration

loss of water through the epidermis which is usually covered with a cuticle; acounts 5-10% water loss

lenticular transpiration

loss of water through numerous pores in the outer layer of a woody plant stem (lenticels)

stomatal transpiration

loss of water through the stomata; accounts as 90% water loss

diffusion

movement of substances from a region of higher concentration to a region of lower concentration

relative humidity

ratio of the actual water vapor in the air to the water vapor pressure at saturation at same temperature and pressure

vapor pressure deficit

difference between the actual water vapor pressure and the water vapor pressure at saturation at the same temperature

extracellular or apoplastic route

water moves between any non-living parts

intracellular route

water moves between living parts

symplastic pathway

water moves from one cell to another through the living parts of the roots

transmembrane or transcellular pathway

water crosses the vacuolar membrane (tonoplast) and the plasma membrane

translocation

long-distance, multi-directional movement of photosynthates through the phloem

phloem translocation

highly significant process that functions to ensure an efficient distribution of photosynthetic energy and carbon through the plant

source

tissue or organ that produces more assimilate than it requires for its own metabolism and growth

sink

net importer or consumer of photoassimilates

phloem loading

transfer of materials from the photosynthetic mesophyll cells into the sieve elements

phloem unloading

removal of these materials from the phloem in the sink

munch pressure flow hypothesis

flow of solution in the sieve elements is driven by an osmotically-generated pressure gradient between source and sink tissues

allocation

regulation of the quantities of fixed carbon that are channeled into various metabolic pathways

partitioning

differential distribution of assimilates to competing sinks

soil erosion

physical loss and displacement of the fertile topsoil

geological erosion

natural erosion process

wind erosion

erosion caused by extreme wind speeds

water-borne erosion

erosion caused by rainfall and run-off

raindrop erosion

erosion caused by impact of rainfall

sheet erosion

erosion due tot sheet or overland flow

interrill erosion

erosion caused by the combination of splash and sheet erosion & occurs in between rills

rill erosion

erosion due to shearing effects of water flowing in rills

gully erosion

erosion hat takes place in channels or gullies which are larger than rills

stream channel erosion

erosion due to stream flow

accelerated erosion

erosion due to human activity

chlorosis

• uniform or interveinal)

• yellowing of leaves due to chlorophyll degradation

necrosis

• tip, marginal or interveinal

• death of leaf tissue

apoplast pathway

• scurose moves through cell walls

• sucrose is loaded into the phloem with the help of active transport

• utlizes ATP to pump H+ against the concentration gradient

symplast pathway

• sucrose travels in the plasmodesmata (connections between cells)

• sucrose can flow down the sucrose concentration gradient

• enters the phloem sieve tube elements where it will be transported to sink tissues