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Re: Stargrass suffering under Zoomeds (fwd)


Cavan reported damaged leaves on his h. zosterifolia grown under bright

I (like several others who have commented) suspect that Cathy Hartland's
reasoning is correct, but I think that Wayne Jones' observation of
damaged leaves under other bulbs was interesting.

Several years ago I had plants that exhibited a number of damage symptoms
when grown under Philips Ultralume lights.  That included black spots on
java fern leaves, lesions on leaves of H. corymbosa and early leaf drop by
several plants, but most noticeably by the H. corymbosa.  The visible
damage was limited to those parts of the leaves that were exposed to
direct light.

I brought this up on the list and found that several other people were
growing plants under the same kind of lights without similar symptoms.
Just the same, I switched the lights out and the plants suddenly stopped
dropping their leaves and the leaves remained undamaged.  I started adding
extra K and Mg to the tank a couple weeks earlier, so there was some
possibility that the changes were a delayed response to the added K and

Paul K. suggested that I put the old lights back to confirm the effect and
eliminate the possibility that the changes were caused by my change in the
fertilizer regime.  I refused because having solved the problem, I didn't
want to back up.  The tank was, after all, in my dining room and the
aesthetics were pretty important.

A year or so later the new lights I put on refused to light, so I put the
old tubes back on until I could get out to buy replacements.  Three days
later when I once again replaced the Ultralumes the H. corymbosa had
dropped almost half their leaves.  I took that as confirmation that there
was some detrimental effect from those specific lights.

Other people reported great success with the same lights, so what could
the problem be?  I still don't actually know.  I suspect that it could be
caused by an interplay between a trace or minor nutrient deficiency and
the enzymes that are regulated by the plants' secondary pigments that
respond to very specific wave lengths of light.

Pretty pure speculation, I know.

Roger Miller