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Necrotic leaf margins (pictures)
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Posted by Teresa_in_MD z7 MD (My Page) on Thu, Jul 28, 05 at 19:18
| Sorry to be posting so much lately...
Two of my plants are being taken from the bottom up by leaves that are slowly dying from the margins inward. There is absolutely no yellowing whatsoever, no wilting and no discolored liquid comes from cut stems. The margins just turn brown and the leaf becomes very dry and the dead material crumbles away - all while the leaves are still attached to the stem. Doesn't appear to be any discernable spotting. Spraying with fungicides and copper seems to be having no effect. Plants have been fertilized sparingly. I have no idea what's causing this and have never had this happen before. Any ideas?
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Follow-Up Postings:
RE: Necrotic leaf margins (pictures)
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- Posted by LizzieA z9 CA Sunset 17 (My Page) on
Fri, Jul 29, 05 at 1:11
| Yes! This is what's happenning to me also. I got on here tonight to post a question about it. My experience is exactly the same as Teresa's. It looks most like the picture of Canker on the Problem Solver/Leaves pictures but there appears to be nothing wrong with the leaf stems or the branches (no canker.) I have early blight on other plants so I know what that looks like, but this one is new to me. Any help out there? |
RE: Necrotic leaf margins (pictures)
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| Teresa and Lizzie, There are two diseases with Canker in the name. One is Bacterial Canker which can be found almost anywhere in the US but ususally more southern than northern, and is characterized not by necrotic lesions on the leaf margin, but by many other symptoms such as dark lesions on the stems, wilting in a certain pattern, fruit infections with specific lesions, etc. The other one is Alternaria Stem Canker which has leaf lesions that are nothing like what is shown here as well as other symptoms and is found almost exclusively in CA. I have leaves with necrotic edges as well, and as long as there aren't any other symptoms I ignore them and usually new foliage is fine. I chalk it up to weather, whether I'm right or wrong. Carolyn |
RE: Necrotic leaf margins (pictures)
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| Well Carolyn, I will surely heed your advice. I too felt the lesions were like nothing I'd seen associated with EB or bacteria but was unsure what to do. It does, however, appear to be spreading which gives me pause. I'll try to remove as much of the dead tissue as I can and keep the fingers and toes crossed. As always, thanks a bunch. Teresa |
RE: Necrotic leaf margins (pictures)
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| Teresa, what was the outcome for those two plants? Did it spread to other plants? I have 18 varieties started, mostly between 6-12 of each and of those I have one variety 'Hawaiian Pineapple' that has a similar problem to the one you posted about. It started with the cotyledons. There is only one other plant that has this problem and it is a cross (not all the seedlings from that cross, just one plant). I'd like to get some advice on whether I should dispose of the plants with the leaf disorder. If it could spread, it's not worth it. See pictures. 
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RE: Necrotic leaf margins (figured out pictures)
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| Here are the pictures that should have been above. Also, forgot to note that the leaf disorder appeared on the cotyledons before the first true leaves emerged, so well before I used any fertilizer. I'm now using Alaska 5-1-1 and 0-10-10 TBSP of each per gallon. My seed starter mix is Promix PGX 
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RE: Necrotic leaf margins (pictures)
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Plants have responses to internal (biotic) & external environmental (abiotic) triggers that involve the different ion salts' homeostasis.
There is an enzyme complex (NADPH-oxidase) that senses oxygen biochemistry.
Special oxygen molecules then develop with the reactive capability to mediate cell signals.
An important regulator of the growth factor (GF) signal is a Copper/Zinc oxygen molecule (Cu,Zn-SOD).
Chloroplasts are affected by abiotic & biotic stress influx of Calcium (Ca++). This Ca++ ion stimulates another reactive oxygen species (H2O2) to be produced, which diffuses into surrounding cells as a messenger to initiate physiological action.
H202 is Hydrogen Peroxide & the Ca++ ion can instigate two opposite types of regulation (ie: positive = generate H202 by activating NADPH & even indirectly producing more NADPH; & negative = stimulate Catalase the antagonist to H202, which breaks down & sets loose an unstably charged oxygen molecule).
What the leaf margin pictures show is oxidative damage on the fringe of leaf growth. A lay explanation is that these are some burned out dead (necrotic) cells.
This is consistent with Carolyn's experience that the plants seem to grow out of this phase , and that this is not a plant disease. In other words the season progresses, the plant adapts & it sorts out the biochemistry it has to live with.
The pronounced occurrence in some tomato varieties, & even their cotyledons, is quite probably due to a minor genetic mutation. Those Reactive Oxygen Species (ROS: like superoxide O2-- & H202 hydrogen peroxide) control some gene expression of proteins that signal the plant (or cotyledon) what to do in it's cells.
Let's go down to the roots for a possible clue to intervention ....
Potassium(K) metabolism is important for feeder root function. A deficiency in K+, whether from lack or lock out by other ions, loads up ethylene in the root tissue.
In case of acute K+ ion deprivation the roots back up system driver is H202. Hydrogen Peroxide activity in this situation is focused next to the root zone of elongation. In other words H202 boosts the genetic activity that makes K+
ions get moving.
Since nutrient salt uptake is ionic the net effect of getting feeder roots to metabolize K ions is to break apart the log jam of locked up ions. The plant's roots can then send adequate Cu,Zn & Ca to the leaf. (Remember, roots feed ion by ion & nobody mentioned their soil analysis - just that they tried to fertilize responsibly.)
A soil drench of the root zone with 1-2 Tablespoons of 3% Hydrogen Peroxide diluted in a gallon of fresh water can be used to try to circumvent the continuation of new leaf necrosis. You will find internet recommendations for higher gardening concentrations & foliar application rates, if inclined.
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RE: Necrotic leaf margins (pictures)
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| Some tomato genotypes show this sort of marginal burn on the cotyledons and leaves when germinated and grown in artificial soil mixes. Once you transplant them out to the field in real soil, the burn symptoms go away on the new foliage. The post above by gringojay gives some insight into what may be going on with the plants. This is a physiological disorder rather than a pathogen caused disease. |
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