SOURCES OF WONDER IN PELARGONIUMS
By Wayne L. Handlos, Ph.D.
“All the variegated plants that I have seen amongst pelargoniums are chimeras, with
the exception of those that are caused by virus infection.” (Tilney-Bassett, 2008)
In Greek mythology, there was a fire breathing dragon calledChimaera. Its body
consisted of lion, goat and dragon parts.
Since at least 1644, occasional plants have been known which appeared to consist of
very different parts/tissues. One such plant was called the ‘Bizzarria’ orange. On
this grafted plant there were leaves, flowers and fruit identical with an orange or
identical to a citron and sometimes the fruits consisted of a compound structure that
was half orange and half citron (or some other proportions of the two species).
Studies have been conducted over the decades in an attempt to understand these unusual
plants. Through experimental grafting techniques, H. Winkler (a German) in
1907 created a plant composed of both tomato and black nightshade tissues. He
called this plant a “chimera.” About the same time (1909), E. Baur (another German)
experimented with zonal pelargoniums with green and white variegated leaves
(plants frequently called fancy leaf by pelargonium fanciers). Through further examination
of the cells and tissues of pelargonium and breeding experiments, he determined
that some of these unusual plants were composed of genetically different
cells. Depending on the arrangement of these genetically different cells within a
plant he described these plants as periclinal chimeras.
1. Guard cells with normal green chloroplasts
2. ‘L’Elegante’ -normal leaf -GWG 3. ‘L’Elegante’ -white leaf -GWW
4. ‘L’Elegante’ -all green leaf -GGG 5. ‘L’Elegante’ - variegated leaf with green marginal cells from LI
In the variegated leaf (or fancy leaf) zonal pelargonium, studies have shown that the
chlorophyll-bearing structures (called plastids or chloroplasts) are found in abundance
in the green portions of the leaf. But in the white, yellow or ivory areas of the
leaf, the plastids are abnormal or do not develop normally; in either case they do
not contain a functional form of the green pigment chlorophyll.
Through a variety of experimental techniques, it has been determined that in the
green and white variegated fancy leaf pelargonium leaves, the various layers of
the tunica and the corpus are genetically different from each other. In the typically
variegated leaf with a whitish margin and a green center, the layer LI of the
tunica produces cells which contain normal green plastids/chloroplasts. But in
the LII layer of the tunica, the plastids do not produce green chlorophyll and the
part of the leaf derived from this layer (that is, the margin or edge of the leaf) is
white (ivory or yellow). The central area of the leaf develops from cells of the
LIII layer (that is, the corpus). If the plastids are genetically normal, they produce
chlorophyll and this tissue in the leaf is green.
In order to understand the variations in the tunica-corpus and their derivative
cells, the layers are designated either G (for green) or W (for white). In the case
of ‘L’Elegante’ which has a green and white variegated leaf, it would be designated
GWG for the LI, LII and LIII layers respectively. The G nature of the epidermal
cells (guard cells) can be seen microscopically or the margin of the leaf
can be screened/examined for the presence of small green areas where an occasional
periclinal division in LI pushes some cells into the region normally produced
by LII (that is the mesophyll) and they then produce normal green chloroplasts.
These plants are referred to as “sandwich chimeras” because the white
tissue is sandwiched between two layers of green tissue. Occasionally
‘L’Elegante’ will produce all white leaves. In these plants the corpus, LIII, layer
has been replaced by white cells of the LII layer through periclinal divisions of
cells of this layer. If there are green marginal flecks such a plant is described as
being GWW. On the other hand, occasionally ‘L’Elegante’ produces all green
leaves. In such plants the LII and LIII layers have been replaced (supplanted) by
repeated periclinal divisions of LI giving the composition GGG. Upon microscopic
examination of the epidermis it has been found that a certain few cultivars
(‘Caroline Schmidt’, ‘Wilhelm Langguth’, ‘Lady Cullum’ and ‘Mrs. Parker’)
have a genetically white epidermis and are designated as WWG.
Occasionally it is possible to obtainPelargonium plants from adventitious buds.
These are buds that develop from structures other than the apical meristem. In
Pelargoniumsuch buds develop frequently from the roots. This is particularly
common in the regal and scented leaf pelargoniums. However, such buds develop
from cells of the inner layers of the root (usually in areas of the vascular
system which would have been derived from the LIII layer). In such plants the
chimeral nature of the plant is lost and the genetic nature of the core tissue is re
1. White shoot of ‘Mrs. J.C. Mappin’ - GWW
2. Marginal green tissue in ‘Mrs. J.C.Mappin’ showing the green potential of LI
3. Butterfly variegation pattern in ‘A Happy Thought’ 4. Butterfly variegation in ‘Crystal Palace Gem’
5. All gold leaf of ‘Crystal Palace Gem’
Now, if you want to breed variegated leaf pelargoniums, remember that the reproductive
cells are usually derived from the LII layer. So if LII is white (W), then
the seedlings from selfed plants will be white. (And unfortunately all white
plants die because they lack chlorophyll and cannot produce their own food supply
to sustain life.) Similarly, if you decide to propagate your variegated leaf.
Pelargoniumby tissue culture, the component cells become separated
(disassociated) so the G cells will produce only green plants and the W cells will
produce only white plants. In either case, no variegated plants result because
each individual plant and its tissues are derived from a single cell and therefore
all cells of that individual are genetically identical.
Most variegated leaf plants will at some time produce aberrant shoots. In zonal
pelargoniums the stems and their leaves will either be all green when LI replaced
LII and LIII (GWG to GGW to GGG), or all white when LII replaces LIII (GWG
The sandwich chimera, GWG, is the most common type giving white-margined
leaves. The green nature of the epidermal cells (and therefore of the cells of LI)
can be determined by examining the guard cells in the lower epidermis. In a genetically
green epidermis the guard cells contain green plastids; in a genetically
white epidermis the guard cells lack green plastids. The presence of small green
segments along the margin of the leaf due to periclinal division of cells of LI also
indicates the genetically green nature of LI and the epidermis. The LII layer is
responsible for the white margin. (Its presence is also confirmed by the appearance
of non-green seedlings from the self pollination of variegated plants.) The
green nature of LIII is confirmed by the green color of the stem and the production
of green shoots from adventitious buds from the roots. Sandwich chimeras
frequently give rise to all green (GWG to GGW to GGG) shoots or all white
shoots (GWG to GWW).
Up to this point, all the chimeras described have been related to the plastids of the
cells. The plastids contain their own DNA and are inherited independently of the
nuclear DNA which is contained in the chromosomes. However, there are chimeras
that are under the control of the nuclear DNA. The “butterfly” leaf pattern in
zonal pelargoniums is a case in point. In these plants, there is a central area of the
leaf that has a different pigmentation from the remainder of the leaf. ‘A Happy
Thought’ illustrates this chimeral type. These leaves have a white central area
with a darker green marginal area. In these plants the LI and LII layers are green
and the LIII layer is mutant and does not produce chlorophyll. From a genetic
point of view, LII is heterozygous for a nuclear mutation and produces chlorophyll;
LIII is homozygous recessive for a nuclear mutation which suppresses
chlorophyll production and is, therefore, white. It has been characterized as
GGPale for LI, LII and LIII, respectively. In genetic terms this is designated as
Pp, Pp, pp, where P is the dominant gene and p is the recessive gene.
In ‘Crystal Palace Gem’, also a nuclear chimera, the leaf is light, yellowish green
with a dark green center. The layers are designated as gold gold and green for LI,
LII and LIII respectively. When the green center is “lost” it would appear that
periclinal divisions have occurred in LII which then replaces the green layer of
LIII and gives the composition gold gold gold.
1. ‘Paton’s Unique 2 ‘Spanish Lavender’ 3. Leaf of ‘Golden Lilac Gem’ and the green leaf of ‘Lilac Gem'
4. ‘Rober’s Lemon Rose’ 5. ‘Madame Thibaut’
Tilney-Bassett also notes that other characteristics of pelargoniums are due to chimeral
arrangements of the cell layers of the apical meristem. Besides the variegation
of leaves, these include layers giving rise to different flower color and differential
growth in various cell layers giving rise to cupped leaves.
Changes in flower color are commonly found in regal geraniums (P. x domesticum)
indicating that there is a genetic difference for pigmentation between different layers.
Amongst the zonals, color chimeras are found in such cultivars as ‘Miss
Burdette-Coutts’, ‘Hills of Snow’, and ‘Mrs. J.C. Mapping’.
Amongst the ivy geraniums (P. peltatum), the cupping of leaves is commonly seen
(as in ‘Golden Lilac Gem’, ‘Evka’, ‘Silver Crown,’ ‘Silver Cascade Pink’) The
differential growth of the different layers appears to be under genetic control.
Variegated leaves that are flat indicate that cupping is not due simply to the differential
production of food in the green versus the white cells.
In the scented geraniums, in particular,P. ‘Rober’s Lemon Rose’ the leaf shape of
plants derived from the apical meristem differs markedly from the leaf form of
plants growing from the roots.
The zonal pelargonium, ‘Skelly’s Pride’ or ‘Madame Thibaut’, with glossy leaves
and fringed petals produces a plant with matte leaves and normal petals when
propagated from root tissue. Fringed petals are characteristic of a number of regal
geraniums and loss of this characteristic would indicate that this characteristic is
also related to a chimeral situation. Similarly, the carnation type of flower in certain
ivy geraniums may be of a chimeral nature.
Plant of ‘Mr. Wren’ showing a normal branch with
and an aberrant branch with all red flowers
‘Mr. Wren’ with white-edged, red petals, when propagated from tissue culture, produces
flowers which are all red. When tested genetically it breeds as a heterozygous
red; no white offspring are produced. The white edge is determined by a gene
for pattern and gives offspring which are either red or patterned. The “New Life”
series of plants would also appear to be due to a chimeral arrangement and these
plants are notorious for changing color
Trichimeras. It can be imagined that with a three layered apical meristem, the genetic
nature of each layer theoretically could be different. In fact, this is true for
several pelargoniums that have been studied.
In the variegated zonal ‘Mrs. J.C. Mappin’ which has a green and white leaf variegation
and whitish flowers, it has been found that LI is genetically green and produces
white flowers. LII is genetically white and produces red flower; LIII is genetically
green and produces red flowers. In crossing experiments this cultivar
breeds as if it had red flowers because the reproductive cells are derived from LII
(which is genetically red) not LI (which is genetically white).
‘Madame Salleron’ another variegated zonal which rarely flowers has been determined
to have LI genetically green and produces long internodes; LII is genetically
white with the ability to produce long internodes; and LIII is genetically green with
short internodes. The loss of flowering ability appears to be related to the loss of
one chromosome so that 2n = 17 (rather than the expected 2n = 18).
Miscanthus -GGG GGW GWG
Poinsettia chimeras Carnation chimeras Explain this!!!
Many of our common ornamental and food plants appear to be of chimeral nature.
These include the many plants with green and white variegated leaves. For example,
variegated Fuchsias, ivies, Hydrangeas, Dracaena, Miscanthus. A number of
apple varieties are chimeral. For example, the color forms of ‘Green Delicious’,
‘Delicious’, ‘Northern Spy’, ‘McIntosh’ and ‘Cortland’. The same is true for many
of our potato cultivars where skin color (brownish-red, red, purple) and surface texture
(smooth vs. russet) and leaf form (simple to compound) are affected. The
common Christmas poinsettia is an interesting case. Here the color is produced in
bracts which are modified leaves which surround the small flowers at the tips of the
stems. Normally the bracts are red (R) and the LI, LII and LIII layers are designated
as RRR. When the plants produce pink bracts, the LI layer does not produce
any pigment and the epidermis is white (W). The genetic composition of the layers
is WRR. The red pigment is seen through the white layer and the bracts are seen
as pink rather than red. In cultivars that have a white edge and a pink center, the
genetic composition of the layers is WWR. Plants with all white bracts have the
composition WWW and no cell layer produces a colored pigment. A further variation
is seen where there are pink bracts with red streaks. In this case the red cells
break through the white epidermis and show their full red color. A similar situation
has been found in the florist carnation. ‘William Sim’ is red (RRR); ‘Pink Sim’ has
a pink epidermis over a red core (PRR); ‘White Sim’ has a white epidermis over a
red core (WRR); ‘Jacqueline’ is orange and red striped (YRR) and ‘Jacky” is orange
So we see that chimeras are more common than one might have assumed and contribute
significantly to the variations we see and cherish in our plants.
N.B. Much of this information comes from the following volumes:
R. Tilney-Bassett. 1986. Plant Chimeras. Edward Arnold, London. 199 pp.
R. Tilney-Bassett. 2008. Variegated Zonal Pelargoniums. Serendipity, Darlington, U.K
This heavy-duty article is one in a series of newsletters concerned with the structure of the plants ofPelargonium.
July 2009—Basic Plant Structure; Jan. 2010—Variegated Leaves; Dec. 2009—Chloroplast DNA;
Dec. 2007—Trichomes; Feb. 2009—Chromosomes; Sept. 2012—Stem Apex; June 2008—Flowers
Links to our website will help to refresh your memory.