In article <caj1i.81$[Only registered users see links. ]>,
Buddy <why.wood.yew@bother> wrote:
I suspect this is somebody's folk etymology for the term "nightshade".
Actually, they consume O2 all the time, but with light, they can
photosynthesize, consuming CO2 and producing sugars and oxygen.
As to actual growth, i.e. producing more and larger cells, they
do that all the time, as long as they have enough light, water,
heat, nutrients, etc, except when dormant, of course.
> Remembering a bit from high school, aren't we talking about ATP/ADP -
photosynthesis and respiration can simultaneously occur - there are
certain plants that have specific adaptations (usually due to heat,
dessication, light, etc.) that either spatially (C4) or temporally
(CAM plants, which I think is causing the confusion here) separate the
influx of CO2 and the process of converting it to sugar. remember
that all living things respire, and so the sugars that plants produce
through photosynthesis that don't go to their structure (cellulose,
lignin, etc.) or shared with symbiotes (mycorrhizal fungi, etc.) are
burned for energy.
photosynthesis takes water and CO2; using the energy from light
converts them to sugar and O2 (waste).
(aerobic) respiration takes sugar and O2; within the organism they get
converted to ATP and CO2 (waste).
It depends how you define plant growth. If you define growth as an
increase in plant dry weight, then the answer is probably no because a
gain in dry weight occurs mainly in the light for photosynthetic
plants, except possibly CAM plants.
However, if you define growth as an increase in size, then many plants
may also grow at night because growth requires water pressure (turgor)
to expand cells. During the day, plants often have lower turgor
because of their rapid transpiration rate (Munns et al. 2000). Munns
et al. (2000) also note that internal hormonal controls can override
plant water status effects on leaf elongation depending on the time
Huber and Hanson (1992) found that leaf expansion occurred mainly at
night for a wild-type tobacco. However, a starchless mutant tobacco
expanded its leaves mainly during the day.
David R. Hershey
Plant Growth Challenge [Only registered users see links. ]
Huber, S.C. and Hanson, K.R. 1992. Carbon Partitioning and Growth of a
Starchless Mutant of Nicotiana sylvestris. Plant Physiology 99(4):
1449-1454. [Only registered users see links. ]
Munns, R. et al. 2000. Water relations and leaf expansion: Importance
of time scale. Journal of Experimental Botany 51: 1495-1504. [Only registered users see links. ]