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Aroid Water Culture

  • Subject: Aroid Water Culture
  • From: "Ron Iles" <roniles@eircom.net>
  • Date: Sun, 2 Jun 2002 21:01:47 -0500 (CDT)

Water Culture of all Spathiphyllum species & cultivars
I have now had a preliminary look at the some of the general literature on root adaptations to water & have rightly or wrongly deduced the following.
Roots need oxygen .  Gaseous oxygen diffuses into roots up to 10k faster than dissolved oxygen.  Roots in well drained soil have both forms available, those in sumberged oxygenated conditions have only the latter, those in anaerobic water logged soils have neither.  In the last case oxygen needed by roots diffuses down from the aerial parts in possible gaseous form.
Roots which live in waterlogged anaerobic soils or submerged continuously have aerenchyma, hypertrophied lenticels, (both speeding gaseous oxygen diffusion downwards from aerial parts) & reduced or no symbiotic microrrhiza.   Water roots seem thicker & whiter than land roots.   Do the water roots also have special histology as barriers against hostile anaerobic conditions?
Does the relative ability of terrestrial plant kinds to adapt to root submergence or waterlogging depend on their capacities to develop those "special" roots?    Do the kinds which develop "water roots" more readily have metabolic mechanisms already waiting for possible inundation?    Does the change from "dry" land roots to "special water roots" need to happen without the the former rotting & making the latter unhealthy?  In the Julius Pot presumably moist air pockets are kept above as the water roots submerged themselves in the water below?  As the new roots grow into water do the upper roots continue to grow or do they become redundant, the whole plant being maintained eventually by "water roots"?   When the water roots are fully developed,  can they grow as well or better on land than the land roots.  Some cultivars & hybrids grown as "house plants" seem more susceptible to root & petiole roots such as Cylindrocladium; could this be because they do not have or cannot grow water roots as easily?  Especially when there are natural species which are not apparently susceptible, could this question be significant in the research being done to make presumably depleted gene pool line bred/inbred cultivars less susceptible to these rots?  And not only Spathiphyllum...?   
Hydroponics & aeroponics are techniques where plant roots are briefly & periodically flooded or sprayed with water. In contrast, in "Water Culture" roots are continuously submerged in artificially aerated water.   Is the last technology most suitable for plants which have "water roots" already or can develop them fast enough to survive or for all aroids?  Is the challenge to encourage the most rapid healthy change from land to water roots?
These deductions provide the challenge to try growing all Spathiphyllum & maybe other aroids with roots totally submerged.  If successful, it could open the floodgates (an apt pun?) for emersed horticulture without need for hydroponics.  By changing culture methods not necessarily "improving" cultivars, would it produce crops more resistant to rots such as Cylindrocladium.   To me water culture allowing parallel fishculture also would be significantly less expensive, controllable, efficient & effective than traditional terrestrial culture.  Indeed, some of the information arriving here in private emails is that many Spathiphyllum species documented in taxonomic treatments & otherwise regarded as more terrestrial by Bunting et al do also grow commonly in rivers, streams & swamps.  Amongst these are members of Section Amomophyllum which originally I felt were not of those habitats.   Now I wonder if most or even all Spathiphyllum species could adapt to a wide range of habitats by changing their root histologies sufficiently fast to meet oxygen needs.   Are the changes in their root morphologies to meet widely varying environmental conditions of taxonomic significance....?   
I hope this short rapidly written treatise is in order for Aroid-L.  I would of course greatly have preferred a dedicated full IAS Members Dialogue Area but that is not available & I continue to request this.  Over the next months I have a wide range of thoughts, questions, theories, hypotheses, observations, conclusions, analyses, concepts to submit for criticism hopefully to stimulate positive helpful debate.
R.B. Iles

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