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  [Aroid-l] Blanching Query
From: ted.held at us.henkel.com on 2006.06.29 at 16:54:58(14372)
Dear aroid horticulturists,

Here I am again being curious.

What is happening when an indoor plant is moved outside and experiences massive blanching? This seems pretty universal for plants, not just for aroids. If the weather is clement, new leaves will eventually appear that are hearty enough to be fully green and lush without any protection. Sometimes those leaves are smaller or more intensely green than the indoor versions. But it means the plant is capable of receiving a full dose of weather and sunlight. It is as though leaves with different endurance characteristics are produced to match a given climate situation. It does not even help if the transition is made very gradually.

I have heard before that this involves a cuticle layer that either inhibits desiccation or not depending on whether or not it is present. But the blanching I refer to does not seem to involve desiccation - except if it is so severe that the leaf dies and the desiccation is associated with necrosis. Plants kept moist and in humid conditions will still blanch.

The reverse is also true - sort of. Plants with "outside" leaves are stalled when brought indoors. Most of the time the outside leaves stay, but when new ones come on they are now of the weaker "indoor" variety. Soon enough the outside leaves fall off, apparently ill-equipped to function in the new climate.

It is not always the case that outdoor leaves die when brought inside. But it is almost always the case for the reverse.

Do we have different chlorophyll types, or internal shading or illuminating structures?

I know somebody knows the answers.

Thanks for indulging me.

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