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Thorns, Spines and Prickles


 you know that plants have their own mechanical defences?

And some of them can cause severe discomfort and even pain. If you get pricked by a thorn, spine or prickle, clean it immediately and watch for infection.

There is something called "Plant Thorn Arthritis" which I will write about soon in another page.

In the meantime, here's what you need to know.



How to Tell the Difference


 


THORNS


THORNS:

- are shoots or modified stems with very sharp, woody points and  appear immediately above a leaf.. or where a leaf would be and each thorn contains a "vascular bundle" (see below)

Hawthorn (Crataegus monogyna),

Quince (Cydonia oblonga),

Buckthorn (Rhamnus cathartica or Frangula alnus) or 

Honey-Locust (Gleditsia triacanthos)

FUNCTION:  a mechanical protection from plant eaters



Thorn Sketch


VASCULAR BUNDLE:

- part of the transport system of tube-like tissues that run through the plant to carry water and nutrition to different parts of the plant..

- shown with red lines in the sketch above and go up the stem and  out the length of the thorn.

The bundles are those dots you see when you cut a  piece of celery (sketch below).




Hawthorn Thorns

Quince Thorn

 Buckthorn Thorn

Honey Locust Thorns


SPINES


   
SPINES

 - are sharp, pointed modified leaves that form spines as the plant evolves, replacing the leaves - especially in plants living in dry conditions as the spines help reduce water loss (Cacti)

Spines appear in the position of a leaf, just below an axillary bud and also contain vascular bundles. 

Barberry  (Berberis)

Black Locust (Robinia pseudo acacia)

FUNCTION: mechanical protection as well as prevent excessive transpiration in plants like Cacti.


SPINE


Black Locust Spines

Barberry Spines

Cactus Spines


PRICKLES



PRICKLES

- are modified hairs (epidermis) that are sharp, woody outgrowths on the stem or cane of a plant but unlike thorns and spines, prickles do not contain vascular bundles.

They are  extensions of the plant cortex and epidermis (outer layer of the stem) and are neither modified stems nor leaves
They are also  easy to remove without damaging the stem or cane

FUNCTION:
 - protection- like grappling hooks for stems to climb over neighbouring objects like trellises or trees

LOCATED: anywhere on the twig or cane

Roses (Rosa)

Blackberries. Raspberries (Rubus)

Rose Prickles



Thorn, Spine and Prickle


"Some people grumble that roses have thorns

but I am grateful that thorns have roses"

Jean-Baptiste Alphonse Karr


Actually roses have prickles.... nevertheless....


Roses

How Roses Grow

Pruning Roses

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