Photo-oxidation & Leaf drop, what do do now?

frog_gidgetApril 26, 2010

Hi there, fig lovers,

I have 2 figs that broke dormancy early, and despite my best efforts to harden off and expose them slowly to sunlight, the leaves are distressed, probably from photo-oxidation. Some are falling off, but i see no new leaves forming to take their place. In another post, I read about seaweed emulsion to help with the stress. What else should i be putting on the containers at this point to help?

I'm brand new at this, and I'd hate to lose these!



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tapla (mid-MI z5b-6a)

Hi, Mandie. If you're interested in what happens during photo-oxidation: high light intensity levels w/o adequate amounts of protective pigments present can cause chlorophyll molecules to rise to a more excited state than normal. If light levels are high enough, the energy that is released as electrons in molecules return to their normal energy state may be sufficient to form oxygen (O2) radicals from regular O2. These O2 radicals are extremely reactive particles that readily destroy chlorophyll molecules. (This is the same O- radical that causes rapid oxidation [bleaching] in organic molecules when we apply H2O2 [hydrogen peroxide]). Evidence of the process is seen in a bleached or whitish appearance of the leaves, and is often referred to as peroxidation.

I'm sorry to say so, but seaweed emulsion isn't going to alleviate the stress. Here is what happened: Your tree used a fair amount of it's energy reserves to push the flush of foliage that was lost to sunburn. Your tree is like a battery in the spring - it has a finite amount of stored energy. There is no way to tell if, after having lost all or a part of the initial flush of foliage, the tree will have enough energy to push a second flush. If all of the leaves are not involved, your tree will almost assuredly recover and be fine by late summer, assuming everything else is OK. If all the leaves abscise, you might be able to judge the likelihood of recovery if you think back to how the tree was growing just before it entered dormancy. If it was robust and growing well, it will probably be able to push another flush, but if it was stressed and just struggling along, the odds are reduced considerably.

Fertilizers and 'tonics' aren't the answer. The tree, lacking ALL foliage, would only be able to produce a minuscule amount of photosynthate - that which the tree is capable of producing in young bark tissue, and will be depending (virtually) entirely on stored energy reserves rather than current photosynthate production. If some of the leaves remain viable, the tree will have the benefit of current photosynthate production PLUS its reserves - so the odds of a quick recovery go way up.

Be patient. Put the tree in the shade and gradually expose it to longer periods of sun. I explained in another post why some leaves that flushed under extremely low light conditions cannot adapt to high photo-intensity levels, and why some leaves that flushed under high light levels will simply be shed under reduced photo-intensity/photo-period in another post not too long ago. I think it was on this forum, but I'm not sure.

If I had to bet, I'd bet on the natural vigor with which figs are endowed to pull it through. I'm sure all of us wish you well. ;o)


    Bookmark   April 26, 2010 at 2:54PM
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