Emersed plants questions

[Nont]

Hi there,

I recently facing a problem where my emersed Echinodorus absorb water too fast with its roots (about 2 hour or so) and leaves plant dried.
Fyi the pots i’m using have no drainage hole and the problem isn’t evaporation either.

This is kind of stupid question but are there any method to keep emersed plant with out soaking roots in the water all the time?

 

[tigertim]

They usually need humidity to grow emersed, i would of thought your location would be fine ? i grow my emersed plants in a aquaruim with the glass sliding covers closed, works perfectly.

 

[kayjo]

I'm confused. You have emersed plants, but their roots are not in water??

 

[Nont]

Sorry for the confusion.
What I meant is that the plants roots are in the water but it absorp all water in the pot with in 2 hour of watering which make whole plant dried out. I wonder if there are other way to prevent this from happening.

 

[Aqua sobriquet]

Sorry for the confusion.
What I meant is that the plants roots are in the water but it absorp all water in the pot with in 2 hour of watering which make whole plant dried out. I wonder if there are other way to prevent this from happening.

Bigger pot and different soil?

 

[Simon Cole]

I would have guessed that the issue is a balance between temperature and humidity. There is a sweet spot for every plant and it is called the <vapour pressure deficit> (VPD). Perhaps these plants open their stomata in response to being watered, and this causes them to dry out subsequently. I would aim for either higher humidity or lower temperature. Echinodorus should have their own curved profile on the <VPD chart> that favours their transpiration rate and preferred growing conditions. If the plant suffers from stress, then it is normal to adjust the VPD to suit recovery. You can get a really cheap humidity and temperature meter for about £3 - I have 5 of them and they all work great. Let us know your temperature and humidity readings if you have them?

 

[_Maq_]

I agree with @Simon Cole. The problem seems to be not with watering but humidity. The plants cannot control the rate of transpiration, i.e. transport of water and dissolved nutrients from roots to leaves. If humidity is low, water quickly evaporates from the leaves.
Many plants, esp. originating from humid equatorial habitats, require high humidity permanently. That's why it's useful to keep them under cover in terrariums / paludariums. On the other hand, some kind of ventilation / air flow is often necessary.
In my experience, Echinodorus plants are generally able to adjust to relatively low humidity (60 per cent or so), but they must be given time to adapt and create fully emersed leaves. Leaves which were created during submersion cannot control transpiration.

 

[Nont]

Let us know your temperature and humidity readings if you have them?

Yes I do have it. Temperature is 31C and humidity is 91% today. Normally humidity here would be about 70-80%.

 

[Simon Cole]

I had a go at putting your results into the VPD calculator from the link above. I'm not sure whether I did something wrong, because this is what I got - but it does illustrate the differences:
Your VPD today = 0.41 (91% humidity, 31 degrees C)
Your VPD normally = 0.91 to 1.37 (70 to 80 % humidity, 31 degrees C)
Hence your transpiration potential would be 2.2 to 3.3 times higher on a normal day.

For most terrestrial plants we know that: a) swings greater than 0.4 can drop yields by as much as 20%, and b) entering the danger zone can cause wilting, scorching, and other transpiration-related stresses.
For emersed tropical aquarium plants we can safely assume that they are far far more sensitive to VPD, both in terms of yield and transpiration-related stress.
Emersed aquarium plants arguably have two stages, transition and post-transition from submersed form, and each should have a different VPD growth profile. We can also assume that they have healthy, high, and low transpirations profiles (curves), in addition to a "danger zone". It is a bit of a pity that nobody has created a VPD chart for emersed growing yet. Really we should pull our resources together and create one as a forum/society.

Here is a quick snapshot of your position on the VPD chart (please ignore the grow guide in the top right because it is for terrestrial plants only). Oh, and I should add that my sad face is because today it is so humid downstairs where I live that <cave spiders are invading my house> and I cannot dry my own laundry - not that the plants would not be happy, because they probably would be. The blue line is just my best guess on where you might want to be right now (recovery):