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Abstract
The apparent photosynthesis of progressively older leaves of Themeda triandra was recorded in a controlled environment by means of gas exchange measurements. Photosynthetic rate increased with increasing leaf age and was maximal in the third fully expanded leaf. Thereafter, photosynthesis dropped sharply, but the photosynthetic rate of the oldest green leaf was still 55 % of that of the most efficient leaf. The implication is that old green leaves can probably still play an important role in initiating regrowth after defoliation of younger leaves.
Uittreksel
Die waarneembare fotosintese van blare wat toeneem in ouderdom van Themeda triandra is in ‘n beheerde omgewing gemoni‐tor dew middel van die meting van gasuitruiling. Fotosintesetempo het met toenemende blaarouderdom verhoog, en was die hoogste by die derde, heel oop blaar. Daarna het fotosintese skerp gedaal, maar die fotosintesetempo van die oudste groen blaar was steeds 55 % van die van die mees doeltreffende blaar. Die implikasie is dat ou groen blare heet waarskynlik ‘n belangrike rol kan speel om hergroei te inisieer na ontblaring van die jonger blare.
Notes
Work was conducted by both authors at the Animal and Grassland Research Institute, Hurley, Berks., United Kingdom, SL65LR.
