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What makes a cactus to be a cactus


What makes a cactus to be a cactus
Photo Information
Copyright: petru damsa (petrudamsa) Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 572 W: 77 N: 699] (2450)
Genre: Plants
Medium: Color
Date Taken: 2001-09
Categories: Cacti
Camera: Minolta HT-SI, Minolta AF 35-70
Photo Version: Original Version
Date Submitted: 2006-01-09 5:48
Viewed: 1013
Points: 28
[Note Guidelines] Photographer's Note
I've seen posted on Trek Nature many pictures with succulent plants with prickles that had been categorized as cacti.
Well, all cacti are succulents indeed, but not all succulents are cacti.

so, what make a cactus to be a cactus?

The most remarkable characteristic, which is found only in cacti is that they developed am unique organ: they produce areoles.
Areoles appear in different places on the plant, depending on the specie and they are composed of two perpendicular buds that welded together and they took the task of giving "birth" of other plant parts. The upper bud produces either the new joints (stem) or the flowers and the fruits; the lower bud produces the spines. A remarkable thing that is done by this areoles is that when organs produced by them (spines, bristles, flowers, joints) are thorned off, no tissue dammage is made to the plant, for they are not connected to the tissue below them. On the other side, breaking spines from roses or euphorbia will directly dammage the plant.

Opuntia genus characteristics

Most of the cacti produce just one type of spines, differing on shape, colour, size, number per areole, etc.
Opuntia has developed two kinds of spines comming out of their areoles: the main spines are usualy bigger and stick well to the plant. There are also a very fine layer of tiny spines called glochids, usually very dense and small but quite strong, that are caduc (they come off the plant very easily, somtime even a moderate wind is enough to blow them off). These are quite dangerous because if touched, they will stick under the skin, producing a nasty itch (learnt that the hard way).
As I know, not long time ago, these glochids were used to make the infamous "itchy powder".

The photo posted today lets you see the areoles, spines and glochids of an Opuntia englemannii plant.
scottevers7, Dave, marjan, red45, Active, livios, thistle, Janice, annagrace, Norok, slrnovice2 has marked this note useful
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Discussions
ThreadThread Starter Messages Updated
To Jancie: my jobpetrudamsa 2 01-11 14:44
To Dave: prickles and spinespetrudamsa 1 01-09 11:53
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Critiques [Translate]

Hi Petru,
Excellent macro with good colors and detail. It shows very well the information you are providing. Excellent nots. Thanks for the education, facisnating stuff to me.
Scott

  • Great 
  • Nico Gold Star Critiquer/Gold Note Writer [C: 209 W: 1 N: 332] (1313)
  • [2006-01-09 9:46]

I like your prickly shot showing a small part of the beauty in nature.

  • Great 
  • Dave Gold Star Critiquer/Silver Workshop Editor/Gold Note Writer [C: 527 W: 47 N: 674] (2171)
  • [2006-01-09 9:46]
  • [+]

Hi Petru!
I love the perspective you presented with this shot! Very nice...;-) You created a beautiful and artistic picture. If it were hanging on my wall I would want the Petru Damsa signiture in the lower left...;-)
Besides the wonderful education I got today, one thing I know about cactus is that my mountain bike tires don't like them...:-( Oh well, I pretty much know where all of them are along my route now. And, if I do get a flat it's just time to drag up and take a break for a short while...;-)
Great shot!
Thanks,
Dave

  • Great 
  • marjan Gold Star Critiquer/Silver Workshop Editor/Gold Note Writer [C: 483 W: 10 N: 362] (2631)
  • [2006-01-09 10:29]

Petru , this is very nice photo even better explanation about cacty. TFS
Marjan

  • Great 
  • red45 Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 2816 W: 75 N: 7977] (26975)
  • [2006-01-09 10:38]

Very interesting note Petru, illustrated by good photo. Nice POV and details. Sharp and abstractive picture :-)

  • Great 
  • Active Gold Star Critiquer/Silver Note Writer [C: 113 W: 6 N: 19] (1231)
  • [2006-01-09 12:34]

Petru, it`s a lovely picture:)
I haven`t seen such wonderful macro for a long time.
TFS :-)
Barbara

  • Great 
  • livios Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 2306 W: 324 N: 4306] (16856)
  • [2006-01-09 12:56]

Petru, this one has an artistic touch.

Excellent contrast, dark bg and colors.

I like sharpness too.

Congratulations.

Lovely shot!
The picture looks very arty and very interesting. Has great colours and not bad quality.
As always, great note from you.
WELL DONE & TFS!

  • Great 
  • nofer Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 1219 W: 367 N: 805] (2225)
  • [2006-01-09 20:53]

Muito bom...!! Excelente nitidez. Fundo preto ficou ótimo!
Tive o prazer de ver uma boa foto e completei seus pontos (50) para o WORKSHOP. A partir de agora você terá um QUADRADO DOURADO ao lado de seu nick. Parabéns e obrigado!
TKS
Reynaldo
Very good...!! Excellent clearness. Black Fund was great!
I had the pleasure to see a good picture and I completed their points (50) for WORKSHOP. From now on you will have a GOLD SQUARE beside your nick. Congratulations and thank you!
TKS
Reynaldo

wow,
Great Macro and composition!

thanks Ana:)

Very interesting notes Petru, I hope I haven't called a wrong succulent a cactus!! Please correct me if I have.
I like your POV showing very clearly all the areoles, spines and glochids that you are teaching us. Very well done, thank you. I have taken notes of what you have said too. TFS.
BTW, are you a teacher?

Great capture, it gives a 3D effect that is fabulous. Perfect DOF here.

Alli

bravo pt nota. foto excelenta.

Nice DOF with good details.
sharpness and dark background is great.

Hi Petru, lovely close-up of this cactus. The detail and light come across really well and I love the composition, it is very artistic. Fantastic note as well. I'd like to see a succulent with spines and a cactus side by side and examine them more closely. Very nicely done :)

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