| Shrnutí: | <p>1. Peperomia magnolaefolia, the main plant material used
in the work reported in this thesis, possesses succulent
leaves which show a periclinal chimera. The anatomy of
the leaves, and the occurrence of 'bud-variations' which
were found in the course of the work is to indicate
that their periclinal struetare is a mesochimera</p>
<p>2. Greening in the yellow leaves which takes place in winter
has been shown to be due, not to the short-days, but to
the reduced light intensities during the winter months. </p>
<p>3. Both green and yellow Peperomia leaves can synthesize
chlorophylls and carotenoids. Their different appearance
is due to the difference in the relative ratios of these
pigments they contain.</p>
<p>4. A study of chloroplast differentiation in Peperomia leaf
tissues has been reported. This showed a peculiar
chloroplast structure in greened-yellow tissue - the
chloroplasts here are incompletely differentiated. </p>
<p>5. The pigments formed in the yellow leaves at low light
intensities, like those in the normal green leaves, are
functional (i.e. photosynthetic). </p>
<p>6. Some evidence has been given to show that the occurrence
of non-green (yellow) leaves is not the reault of faster
chlorophyll degradation of some leaf-tissues. </p>
<p>7. Studios on the incorporation of glycine-2-<sup>14</sup>C into
chloroplast pigments of Peperomia leaf discs have been
reported. These showed unexpectedly higher levels of
labelling of a yellow terpeniod 'spot' (carotenes) than
of chlorophylls. A tentative (but plausible) explanation
has been given for this observation (i.e. the almost
complete absence of incorporation of <sup>14</sup>C from the
labelled glycine into chlorophylls). </p>
<p>8. In terms of the incorporation of <sup>14</sup>C from labelled
glycine into 'chlorophyll precursors', chlorophyll
synthesis is faster in green than in yellow leaves. </p>
<p>9. The rate of bleaching in the yellow leaves appears to be
too high, compared with the rate at which chlorophyll
is synthesized in them. It is therefore probable that
these leaves appear yellow at high light intensities
because the rate at which the pigment breaks down is
too fast to make chlorophyll accumulation possible. </p>
<p>10. The control mechanism probably affects chloroplast
differentiation too. Where (as in green tissue)
complete chloroplast differentiation is possible,
chlorophyll synthesis is high enough to permit
chlorophyll accualulation. In yellow tissue, the
control factor (or defect) inhibits complete chloroplast
differentiation and/or reduces the rate of chlorophyll
synthesis, thus making chlorophyll accumulation at
high light intensities impossible.</p>
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