The Lazy Plant Hypothesis

Tom Barr

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I have long held that a plant's organ's will take nutrients that are closest to it, thus the leaf organs will take from the water column and that the roots would take nutrients from the sediment.

This means that the plant does not need to transport nutrients from one organ to the other, there is no time delay for nutrient demands.

Thus there is no nutrient competition for nutrient sinks within the whole plant.

While many have attempted rather poorly to argue against this hypothesis, none have shown any evidence nor logic that it is wrong.

The plant is lazy. If given a choice, why would it transport nutrients when it does not have to?

Unlike terrestrial and emergent plants, submersed macrophytes have both the foliar and root/rhizoid sources.

In many natural systems, the plant is forced to translocate nutrients etc from the sediment to the apical meristem due to the lack of a water column source of nutrients(Barko et al, 1990,1991, 1993, 1994, Madsen Cedergreen, 2001).

When dealing with transport and partitioning within the whole plant, if the plant does not have to transport PO4 from the sediment all the way the entire length of the plant, it is an obvious observation that this will require less energy, less demand on the vascular system for nutrient relocation, and better response times between the nutrient sink and the source.

Far too often such debates over nutrient methods falls into the trap of water column versus the sediment sources.

This is a much too simplistic arguement.

There is a third option: both locations.

Looking at the interactions (using a radomization design+ ANOVA, AMOVA and PCoA's) between these locations can allow folks to know specially what ratios are ideal for specirfic plants.

Say 35% for sediment and 65% for the water column is the ratio of total nutrients for Heminathus to produce optimal growth.

For another plant, say 80% sediement and 20% of the water column and so on.

Other statistical methods using clustering could even further advance the methods and understanding of how plants respond to the various locations of nutrient sources.

At some point, I will do these experiments and stat's, just not sure when:D :p

There are so many really cool ideas, test to do and so many questions.

But back to the lazy plant hypothesis.
It makes sense on a much more basic level, providing good nutruients at all locations for every plant organ(Root, stem, leaves etc).

This maximizes the nutrients sources to the nutrient sinks, thus the plant can be lazy and still grow at a maxmimum rate.

It also provides a high degree of dosing/fertilization wiggle room.
If you forget to dose the water column/sediment, there's a backup.

Give these arguements, the obvious solution is to have ferts in both locations are stable non limiting levels for the best plant growth.

Regards,
Tom Barr
 

morphriz

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Apr 14, 2006
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Karlstad, Sweden
Hi Tom,
are there any data or studies on the N uptake capabilites of the leafes of aquatic plants? Like for instance presense, activity level and distribution of nitrate reductase?
s. Mattias
 

Tom Barr

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Yes, there are several studies, duckweed is always used, but I think other plants such as rice are used and perhaps others.

Regards,
Tom Barr