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The culms have all the nodes!

One of the characters that marks out the Poaceae, the grasses, is the node.

Grass node

Grass node

Grass nodes are the  funny “knobbly knees” on the grass culm (culm=the grass flower stem) and nodes are usually easy to spot. They maybe green or shades of brown or even reddish, round or elongated, hairy or glabrous.

Technically the node is the point at which two successive internodes meet and from whose meristematic tissue (= the intercalary meristem) leaves, adventitious roots and branches arise.

Meristematic tissues are cells or group of cells that have the ability to divide. These tissues in a plant consist of small, densely packed cells that can keep dividing to form new cells which form new leaves, roots and branches etc.

So, the nodes are found on the grass culm, and the culm is the flowering stem of the grass and therefore is quite unlike the smooth node-less flowering stems of rushes or sedges or other monocots – hence the useful monocot ID rhyme: “sedges have edges, rushes are round, and grass have nodes right down to the ground!”

 

Dr M has been investigating the value of the node for identifying grasses, and while this work is ongoing, Dr M is delighted to present here, for the first time, a collage of grass nodes! Hover your cursor over each image to see the identity of each node!

(NB these images are not to any common scale, so relative sizes between images can not be assumed).

 

 

STOP PRESS!  To accompany this node-fest Dr M is composing a poem: “Ode to the Node”, which he will post soon!  Keep your Poaceous eyes and ears open!

 

4 Comments

  • Tim

    Hi Dr. M. Your YouTube videos are wonderful and got me really interested in grass i.d. The grass in these images seemed to key out to common bent. Is this the correct id? http://www.ispot.org.uk/node/361056

    • DrM

      Tim, thanks for the comment. Your grass images are great, I like the way you include a ruler for scale (I will have to do that in my future posts!) and the microscope images are very helpful. You can see very clearly 1 floret per spikelet and the inflorescence is a branched panicle and the leaf blade is flat and (probably) pointed which all indicates the genus Agrostis the Bent Grasses. Your ligule picture is a bit unclear, but if the ligule is shorter than wide (and I think it is) then you have Agrostis capillaris (Common Bent) just as you suggested! Where did you collect the plant? And which key did you use? Keep up the good Poaceous work! Dr M

      • tim

        Thanks for the very quick reply. I live in N. Ireland and the grass was collected from a roadside verge. I was working from the basic key in Collin’s Flower Guide, which seemed to work quite well. When i wasn’t sure of what a term meant in a couplet, I jumped to a grass image that a couplet would have eventually led to and tried to work out what was being described. Is this a reasonable key, or is there a better one? Thanks again! Tim.

        • DrM

          Tim, I assume you mean David Streeter’s Wildflower Guide which is great as it covers all vascular plants (Francis Rose Wildflower key is good too, but only covers the dicots). There are more advanced books for grasses, as you will see from my Poaceae posts, but stick with David Streeter until you want to venture deeper, he does a good job, it obviously works for you (my Students find it good too) and it’s so cheap in paperback! Dr M

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