Oxygen uptake:

Dark respiration: in mitochondria

water production, CO2 release

ATP production

inhibitor: KCN

Photorespiration: in chloroplast, peroxisome, mitochondria

oxygen cycle, CO2 release

ATP consume

inhibitor: DCMU

decreased photosynthetic efficiency

Alternative respiration:

Mehler reaction (1951): in chloroplast (PS1), O2 → H2O2

No CO2 release

promote photosynthetic efficiency

The dural function of water-water cycle:

1. scavenging active oxygen, then reinforce the CO2 assimilation

2. safe dissipation of excess photon energy

Mehler

lighting

P. 274 ~ 275

¤ Respiration rate

depends on the species and growth habit of the plant, the type and age of the specific

organ, and environmental variables, such as temperature, nutrient and water supply.

Whole plant:

on a fresh-weight basis: generally lower than animal’s rate

isolated plant mitochondria:

as fast as or faster than mammalian mitochondria

Plants respire roughly half of the daily photosynthetic yield

tropic plants: higher normal respiration (consumption of 70~80% daily PS gain)

younger vs. older trees (photosynthetic/nonphotosynthetic tissues)

lose 1/3 vs. 2/3 of their photosynthate as respiration

Photosynthesis rate (Max.) Photorespiration rate normal respiration rate

[chloroplast] [C, M, peroxisome] [mitochondria]

Different tissues and organs respire at different rates

Environmental factors alter respiration rate : P. 277 ~ 278

O2:

the Km for oxygen of cytochrome c oxidase is below 1 M

the oxygen concentration of aqueous solution is 250 M (21% O2 in air)

water saturation, flooded (diffusion limitation) [O2]

hydroponic culture: O2 supply

aerenchyma: intercellular air spaces from leaves to roots

pneumato(de)phores, trees that grow in mangrove, swamps

temperature:

T, respiration rate ( 0 to 30°C)

Q10, short-term; if long-term, acclimated [commercial Q10]

too low, decreased respiration rate, stimulated stored starch degradation

optimum storage temperature (7~9 °C for potato), too high or low

CO2: 3 to 5%, inhibit respiration (optimum storage: low temp, low [O2]) enrichment ? artificial biosphere’s result: [CO2], respiration rate/biomass (?)

Cytoplasmic male sterility (cms): p. 276

the presence of distinct rearrangements in their mtDNA,

a non-Mendelian fashion

do not form a viable pollen, prevent self-pollination

example:

a unique 13-kDa protein, URF13 in cms line of maize

+ Hm-T-toxin is produced by fungus Bipolaris maydis (Cochliobolus

heterostrophus)

produce pores in the inner Mito. Membrane, loss selectivity, corn leaf

blight

Nowadays:

mechanical detasseling, which prevents self-pollination.

Lipid :Two type of glycerolipids

1. triacylglycerols, the fats (saturated FA) and oils (unsaturated FA),

are stored in oil bodies of most seeds (lipase hydrolysis)

are converted into carbohydrates in germinating seeds

2. glycerolipids (phospholipase x hydrolysis)

the main structural lipids in membrane

two types: glyceroglycolipids and glycerolphospholipids

are precursors of important signaling compounds

Lipid bodies, referred to as osmiophilic bodies or plastoglobules, are ubiquitous structures in the stroma.

Plastoquinone Tocopherols (vit E)