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Discussion Starter · #1 ·
Here's some info

2002, The American Bryological and Lichenological Society, Inc.

Universidad de La Rioja, Complejo Científico-Tecnológico, Madre de Dios 51, 26006 Logroño, La Rioja, Spain E-mail: [email protected]


The effects of four increasing levels of KH2PO4 on the physiology of the aquatic liverwort Jungermannia exsertifolia subsp. cordifolia were analyzed in the laboratory in the short term (15 d). The accumulation of P and K in the liverwort tissues was influenced (ANOVA) by the level of KH2PO4-enrichment and was significantly higher in the more enriched culture solutions. However, only the concentration of P was influenced by the effect of time (ANOVA), and the gradual P accumulation throughout the culture period contrasted with the fluctuations observed in K accumulation; these were presumably due to the higher liability of K to be leaked from the cells. Our results suggest that the analysis of P in transplants of J. cordifolia may be a useful bioindicator of short term water eutrophication both in the spatial and the temporal scales, although the highest PO43− concentration used in this study (20 mg liter−1) may induce a P saturation in J. cordifolia tissue (0.53% DM). The rates of net photosynthesis showed a significant quadratic regression with the tissue P concentration, which might resemble the action curve of mineral nutrients. Using this regression as an indicator, there was no clear deficiency zone, probably due to the relatively high tissue P concentration initially found in the liverwort. The lack of stimulation of net photosynthesis with increasing tissue P could be due either to a deficiency in other mineral elements such as N, or to an intrinsic inability to use the excess of nutrients. The decline in net photosynthesis when the tissue P concentration exceeded 0.45% DM could be interpreted as a toxicity process. Chlorophyll concentration was not affected by P enrichment, but the decline in the chlorophyll a/b ratio and in the proportions of chlorophylls to phaeopigments, together with the increase in the proportion of carotenoids to chlorophylls, suggested also P toxicity. This phenomenon needs further investigation to be confirmed in other species and conditions, but it may help to explain the disappearance of certain aquatic bryophytes in eutrophicated water courses. The physiological effects of increasing tissue K concentration (decreases in the rate of dark respiration and in the chlorophyll a/b ratio) were slighter than those of P, probably because the accumulation of K was lower than that of P (1.44 and 1.96 times the initial value, respectively). In a different experiment in which J. cordifolia was cultured in P-enriched aerated and non-aerated solutions, anoxia caused a strongly diminished P accumulation in the first three days, probably because the mitochondrial respiration was blocked. Then, a clear net loss of P from the liverwort tissues was observed, maybe caused by membrane damage.

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Discussion Starter · #4 ·
Production of O2 is considered growth from plants, algae in aquatic ecosystems, more O2=> more growth and oprimary production.
Even if your eye cannot tell where the growth is occuring, if the plants are fixing carbon, they will produce O2.
More Carbon fixed, more O2.
It's a good indicator and has been used as a determinant in measuring primary production in many research papers.

Dry weight is another method.
Both methods have their good and bad points. Typically, good research uses several methods to arrive at some conclusions.

But I did find some aspects of that paper very relevant to our discussion about the effects of P on N and supported some of your observations.

The nice thing about liverworts Riccia etc are they are great for dry weight studies and wet weight studies since they don't have roots and that whole substrate nutrient source thing is removed from the equation.

But then what role does the substrate play with all these other plants that do have roots?
So while the liverworts are good for some things, they certainly will not answer all of the question adequately, we need several nmethods to get to the bottom or at least get a better understanding.

I'm going to do a paper for an article on N cycling in aquatic ecosystems so I'll certainly touch on a few of these exchanges and also be doing a more investiagtive research into the literature.

Tom Barr

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Discussion Starter · #6 ·
The Calvin cycle does not involve evolution of O2.

The light reactions: they produce the reduction power for making carbohydrate sugars. Without that, the Calvin cycle will not work.

P is used a great deal in ATP-ATD the main energy source for cells.
NADPH-NADP also uses P.

The base sugars that plants use for storage are rich in PO4.

The addition of PO4 and increases in pearling seems to be more a fuction of ATP/NADPH and simpler compounds, these are quickly made.

The cell would not fix more CO2 if it's PO4 deficient, it shuts down it's CO2 fixing(reduction) and slows things down, "idles" till there's enough PO4 to resume full production. So it's not lost or wasted, it never really gets taken in. The plant cell is finely tuned to changes and environmental inputs, it'll down regulate things if there's not enough/too much etc.

N enters as NO3 or NH4. The NO3 is reduced into NH at the cholorplast cell wall and is very quickly converted from NO2=>NH4 as NO2 is toxic to plant cells internally.

NH4 is then converted into Glutamine via glutamine synthase. There are two types of GS(glutamine synthase), one in the cholorplast and an external one that plays a role in NH4 from the environment rather than from reduction of NO3.

Most of these studies are on agricultural crops but should apply in most cases to aquatic plants as well at this biochemical level.

Finding hard empirical data on aquatic plants is difficult.

Here's a few diagrams from UC Davis and some general test questions.

N cycling: guides/nutrient uptake/12nutruptake2.html

And here's a good one for you for NH4 and NO3 assimlation and rates etc:

This is a good site for some of the comments on lakes and plants:

Note Mn and NO3.

Here's something that might bother you also about high CO2 and NO3

You read all that, and you'll have a good understanding about plant biochem or a headache:) Seriously, there are good info in each one of these sites.

These will help understand and argue for various observations in aquatic plants not just with N or P, but also with K, CO2 etc.

While we often want to narrow things down to one nutrient etc, it's very often several.

Enjoy, now I have to prepare fer da genetic class I have to teach, Fruitfly fun:)

Maybe I'll post some of these over on the APD to stir some disccusion up there also.

Tom Barr
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