Quote:
Originally Posted by Rob
... Is there any correlation between edema and the mix materials? ... I am curious about others' experiences with the causes of edema.
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That's a good question...
My understanding of edema is that it occurs when there is a sudden reduction in transpiration which creates an imbalance between water uptake and water loss with a subsequent overload of turgor pressure in leaf cells causing cells to burst and form water-soaked blisters. This can occur due to a closing of stomata caused by lack of sunlight from heavy overcast, or by a sudden change from warm dry air to cool moist air which drastically reduces the transpiration efficiency of the plant even if the stomata are open.
Actively growing plants are most likely to be affected, as are plants in warm moist soil. So back to the question about soil mix - how fast a mix drains and dries out can be a factor, as well as the time of year when plants are pushed with fertilizer. Anticipating a moist cold front and letting pots dry down to the wilting point in advance of the weather change, and avoiding watering during these times, may help to reduce the occurrence of edema in sensitive crops like geraniums for example.
But geraniums are easy compared to agaves - how does one wilt an agave? And would that work with an agave to prevent edema??
Most edema studies have been with commercial greenhouse crops and not with succulents or with CAM plants...
And what about plants that can switch CAM on and off, and do agaves do that???
In dicots edema is normally found on the lower leaf surface, but again agaves are different and show damage on both sides of the leaf.
And is this agave damage really just edema? It definitely
looks like more than just edema, especially in Matt's photos...
Like Matt, I am not completely convinced, and it may be something more complex though edema or edema-causing conditions may be a factor...
I wonder if wild agaves ever exhibit the same damage - anyone know?
Peyton
P.S. The attached photo shows some damage on
Aloe dichotoma caused by cool wet overcast conditions a month or two ago...