A Close-up View of a

Lantana Cultivar


Lantana camara 'Lemon Cream'


by Brian Johnston   (Canada)

Lantana camara is native to the tropical regions of the world, where it exists as a rugged evergreen shrub that grows as tall as 2 m.  The cultivar studied in this article couldn’t be more different!  For more than 500 years, artificial hybrids have been developed in Europe, and other locations, until today at least 100 different forms and varieties exist throughout the world.  In most hybrids, the flower colour changes with age, from the original yellow, to pink, white, or red, depending on the variety.  Some hybrids however, such as the one photographed here, have a yellow band at the mouth of the corolla tube which is thought to be a visual cue to pollinating insects.  These hybrids have a constant colouration.

The cultivar Lantana camara ‘Lemon Cream’ is diminutive in size.  The flower head shown above is approximately 3.5 cm in diameter, and the plant is 15 cm high.

Two bud-stage flowerheads, called umbels can be seen in the image below.  Notice the ring of green bracts (modified leaves) beneath each umbel.  The bracts form the flowerhead’s involucre.



Above the involucre bracts, there is a mound composed of smaller bracts.  There is one of these bracts for each flower in the flowerhead.  If you look closely, you can see a white flower bud above each bract, near the base of the flowerhead.



As time passes, these white, to pale-yellow buds increase in size until they dwarf their associated bracts.  The buds that form the outermost ring of the flowerhead are the largest, and these have a darker yellow colouration.  Some references describe Lantana buds as having a square shape, but to me they appear like miniature bow-ties!



When the flowers finally bloom, they do so in order from the outer ring to the centre of the flowerhead.  The fused petal tube, (corolla tube), has, as mentioned earlier, a yellow ring at the point where the narrow tube flares out to form the trumpet-shaped flower top.



Two photomicrographs showing the cellular structure of one of the flower’s fringe “petals” can be seen below.  The central cells appear spherical in shape, while those at the petal’s edge appear hair-like.



The lower surface of a petal is covered with long hairs that appear, at higher magnification, to have extremely small projections on their surfaces.



Different developmental stages can be seen in the flowerheads shown below.  Notice that no reproductive structures are visible in the fully mature flowers.  These are hidden deep within the corolla tube of the flower and are therefore inaccessible to insects without a long proboscis. 





A closer view shows additional details of each stage, from bud to flower.





Viewed from beneath, the ring of involucre bracts can be seen clearly.  Notice the length of each flower’s corolla tube.



Bright lemon-yellow flowerheads contrast with the surrounding green leaves.





Positioned deep within the corolla tube is the flower’s pistil.  At the top is the stigma which accepts pollen from a visiting insect.  Beneath the stigma is the style that supports it.  Older styles have a red colour (left), while younger ones are pale green (right).



The photomicrograph on the left below, shows a higher magnification view of the many hair-like projections on the stigma’s surface that help catch, and retain pollen grains.  The image on the right shows the base of the style, and the swollen ovary (seed producing organ).



Lantana leaves are lance-shaped (lanceolate), and have a glossy green upper surface with an attractive vein pattern.



The lower surfaces of leaves are covered with relatively long, sharply pointed hairs which are concentrated on the prominent veins.  In the last image, pollen grains can be seen clinging to the surface of these veins.





Lantana camara ‘Lemon Cream’ has unusually shaped buds, and colourful flowerheads that make it an attractive garden flower.

Mystery – “The case of the missing stamens.”  Readers may wonder why I failed to include photomicrographs of the flower’s male stamens in this article.  It was my intention to do so, but I couldn’t find any!  I carefully dissected several corolla tubes, expecting to find anthers with their filaments attached to the inner corolla tube.  They simply weren’t there!


Photographic Equipment

Approximately half of the photographs in the article were taken with an eight megapixel Canon 20D DSLR and Canon EF 100 mm f 2.8 Macro lens.  An eight megapixel Sony CyberShot DSC-F 828 equipped with achromatic close-up lenses (Canon 250D, Nikon 6T, and Sony VCL-M3358 used singly, or in combination), was used to take the remainder of the images.

The photomicrographs were taken with a Leitz SM-Pol microscope (using a dark ground condenser), and the Coolpix 4500.


Further Information

Lantana

http://plantanswers.tamu.edu/publications/lantana/lantana.html

Notes on poisoning – Lantana camara

http://www.cbif.gc.ca/pls/pp/ppack.info?p_psn=232&p_type=all&p_sci=sci

Lantana camara

davesgarden.com


A Flower Garden of Macroscopic Delights

A complete graphical index of all of my flower articles can be found here.


The Colourful World of Chemical Crystals

A complete graphical index of all of my crystal articles can be found here.


 All comments to the author Brian Johnston are welcomed.


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