International Aroid Society

I am not convinced any of the "ecological" explanations even begin to touch the question!

There is usually a tacit assumption that perforated leaves have evolved from unperforated leaves - hence the question 'why holes?'. But maybe they have evolved from leaves with had dissected margins - in which case the question becomes why=2C in their development=2C are these leaves dissected from within the margin instead of at the margin?

Roughly speaking=2C the leaf of a mature M. deliciosa has three hierarchical sets of holes - a set very big ones whose thin edges break as the leaf unfolds creating the major dissections of the leaf=2C a set of medium holes and a set of small holes near the midrib. Philidendron bipinnatidum on the other hand=2C also roughly speaking=2C has (up to) three sets of marginal lobes=2C a set of very big ones making the major divisions=2C which are themselves lobed (the mid-level divisions) and a few of the finest "lobes on lobes on lobes". =3BThe leaves of these two common examples are=2C in a sense=2C 'inside out' versions of each other.... =3B

Looking at it primarily as an evolution of development (interior functional) question rather than an adaptive-ecological (exterior functional) question leads one off in a rather different direction [see Hay &=3B Mabberley in Bot. Jahrb. Syst. 113 (1991) 339-428] :-)

Date: Sat=2C 25 Feb 2012 20:38:10 -0800
From: jason.hernandez74@yahoo.com
To: aroid-l@www.gizmoworks.com
Subject: Re: [Aroid-l] Holes

No one has figured out definitely what is the function of holes=2C but several ideas have been proposed in the literature. =3B One -- which I consider the least plausible -- is to fool insects: supposedly=2C insects see the leaves appearing already to have been eaten and move on=2C as if to avoid a plant with higher concentrations of defensive compounds=2C or possibly competition from other insects. =3B This theory does=2C however=2C raise questions about how important visual cues are to herbivorous insects. =3B Another idea is that the holes increase air circulation around the leaves=2C possibly providing "air conditioning" or facilitating gas exchange. =3B To me this seems more likely.

Jason Hernandez

Naturalist-at-Large

Date: Fri=2C 24 Feb 2012 20:55:14 -0400
From: "John" <=3Bcriswick@spiceisle.com>=3B
Subject: [Aroid-l] Holes
To: "'Discussion of aroids'" <=3Baroid-l@www.gizmoworks.com>=3B
Message-ID: <=3Bauto-000487290283@cgpfe4.candwall.com>=3B
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Can anyone say what might be the biological purpose of leaves with holes in
them? =3B A typical example would be Monstera deliciosa.

John.

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