Hi all,
i would say yes, the length i imagine would depend on type of plants and nutrients ect, the bigger it grows the bigger the root system.
Yes, that is basically correct for most plants that normally grow as emergents (plants like
Echindorus, Cryptocoryne, most
Hygrophila spp. etc.) and some true aquatics
Vallisneria.
The situation is slightly different for plants like aquatic ferns (
Bolbitis heudelotii, Ceratopteris spp.), all mosses and liverworts, plants that naturally grow as epiphytes or lithophytes (
Anubias spp.,
Bucephalandra spp., Java Fern etc) in very wet conditions, and finally a lot of true aquatics that don't ever experience non-aquatic conditions (
Ceratophyllum etc.) where roots, or analogous structures, don't actually function as roots, but purely as physical anchors. These take all their nutrients from the water column via their leaves.
Most floaters are similar in that they do have functioning roots (or modified fronds in
Salvinia spp.) but take nutrients purely from the water column.
As a general rule whenever a plant has functioning roots (for nutrient acquisition), the plant will apportion resources dependent upon the availability of nutrients. If the plant is growing in nutrient rich conditions they will grow larger all around, but they will grow proportionally fewer, smaller roots and if they are growing in nutrient poor conditions they will be smaller (often by x10) all around, and apportion more resources proportionally to root growth.
You can see this quite clearly with a floater like
Pistia or
Limnobium and
Limnobium was actually used as the model organism to look at nitrogen uptake by root hairs. From Gilroy, S & Jones, L. (2000) "Through form to function: root hair development and nutrient uptake"
Trends in Plant Science, 5:2, pp56–60.
Available at <
http://www.sciencedirect.com/science/article/pii/S1360138599015514>
Root hairs project from the surface of the root to aid nutrient and water uptake and to anchor the plant in the soil. Their formation involves the precise control of cell fate and localized cell growth. We are now beginning to unravel the complexities of the molecular interactions that underlie this developmental regulation. In addition, after years of speculation, nutrient transport by root-hairs has been demonstrated clearly at the physiological and molecular level, with evidence for roothairs being intense sites of H+-ATPase activity and involved in the uptake of Ca2+, K+, NH4+, NO3-, Mn2+, Zn2+, Cl- and H2PO4-
In the substrate this is more difficult, and in nearly all systems the actual uptake of the ions is often going to be dependent upon a complex interaction with microbial symbionts.
I think these should be available to all: "Plant nutrient-acquisition strategies change with soil age" <
http://www.sciencedirect.com/science/article/pii/S0169534707003576> & "Roots, water, and nutrient acquisition: let's get physical"<
http://www.sciencedirect.com/science/article/pii/S1360138512001719>
cheers Darrel
