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Jonathan B. Marder MARDER at agri.huji.ac.il
Tue May 31 01:05:21 EST 1994

In article <2s7re0$k2l at vixen.cso.uiuc.edu> csogren at prairienet.org (Carolyn S. Ogren) writes:
>Subject: absorption
>From: csogren at prairienet.org (Carolyn S. Ogren)
>Date: 28 May 1994 16:27:44 GMT

>The absorption spectrum for plant chlorophyll shows that there is
>little absorption of green light. I understand that is why plants
>are green. But why don't plants absorb, use, these wavelengths?
>Isn't this a "waste of a valuable resource?
Don't be fooled by Absorbance spectra - absorbance is a logarithmic
scale.  If a single leaf transmits 63% of the green light (0.2 optical
density), then a stack of five leaves (1 O.D)would transmit only 10% i.e.
90% absorbed AND USED.  In practice this means that crop canopies absorb and
utilise green light for photosynthesis.

BTW John Cheeseman is right in saying that some of the green absorbance is due
to accessory pigments (which channel the energy to chlorophyll).

Jonathan B. Marder                 '
Department of Agricultural Botany  |     Internet: MARDER at agri.huji.ac.il
The Hebrew University of Jerusalem | /\/ Bitnet:   MARDER at HUJIAGRI
Faculty of Agriculture             |/  \ Phone:    (08 or +9728) 481918

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