leaf resupination, was Alstroemeria pulchella/psittacina

Jane McGary janemcgary@earthlink.net
Fri, 01 Feb 2013 12:05:04 PST
Nhu wrote,

>Alstroemeria and Bomarea are relatives, they share a common ancestor.
>Bomarea stems climb on other plants and if you look closely they actually
>twist their leaves so that the leaves face the sun (I went out to look at
>my plant just now and it did exactly that!). As a result, some of the
>leaves will be resupinate (twisted), others will be non-resupinate
>(regular). This may be the case with Alstroemeria too, but they don't climb
>and the chances of them falling over isn't too great.

Alstroemeria species are varied in size and growth habit, and 
although they have no active climbing mechanism such as grasping 
tendrils and petioles or twining scapes, in nature some of the larger 
ones grow among shrubs and ascend through the shrubs, leaning on them 
(scandent). I have seen Alstroemeria aurea emerging from a thicket of 
introduced Himalayan blackberry in Chile at a height almost 2 meters, 
although A. aurea more typically grows in woodland and open hillsides 
and is shorter. The flowering stems, which have more scale-like 
leaves, usually are stiffer and longer than the sterile, leafy stems, 
and thus better able to get the flowers up where pollinators (which 
include hummingbirds) will be attracted to them. In species where the 
leaves are resupinate, this twisting sometimes is at the base and 
sometimes more toward the mid part of the leaf. It's a diagnostic 
feature (if we can regress to morphology!). I don't think it changes 
depending on the site where the plant is growing. The reverse of the 
leaf, which turns upward when the leaf is resupinate, tends to have a 
lighter appearance than the upper surface; I think this is from very 
short, fine hairs. Would this interact with climatic factors, such as 
high insolation and drought?

Jane McGary
Portland, Oregon, USA

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