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We started with Plant Morphology in class (specifically, the morphology of angiosperms).

My teacher's provided us with the following terms and their definitions.

  • Phylloclade

    A modified stem that is flattened or cylindrical and capable of unlimited growth. They are green and capable of photosynthesis. Examples include; Opuntia, Epiphyllum, Casuarina, Euphorbia.

  • Cladophyll (also called a Cladode)

    A modified stem capable of limited growth. They are green and capable of photosynthesis. They bear an axillary bud at the their middle, from which flowers develop. Examples include; Ruscus, and some Asparagus species.

No mention of the term "Phyllode"...yet.

Now I'm sure I understand the definitions provided, however, I'm beginning to seriously question the validity of those definitions.

Apparently, these terms aren't documented very well, and after two hours of constant Googling, I arrived at:

  • Phylloclade (From the Wikipedia page of the same name)

    Phylloclades and cladodes are flattened, photosynthetic shoots, which are usually considered to be modified branches. The two terms are used either differently or interchangeably by different authors. [Examples provided]: Ruscus, Phyllanthus and some Asparagus species.

  • Cladophyll (From the Wikipedia page for "Petiole")

    In some plants, the petioles are flattened and widened, to become phyllodes or phyllodia, or cladophylls and the true leaves may be reduced or absent. Thus, the phyllode comes to serve the functions of the leaf. [Examples provided]: Some Acacia species.

This is annoying, seriously.

According to the definitions provided by my teacher, we're dealing with something called a "Phylloclade" and something else called a "Cladophyll" (= "Cladode"). They don't mention the term "Phyllode", though.

Based on the Wikipedia definitions, however, we're dealing with something called a "Phylloclade (= "Cladode", if you ignore minor d̶i̶s̶r̶e̶p̶a̶n̶c̶i̶e̶s̶ differences in their definitions, which are mentioned later on in the Wikipedia article), and something else called a "Cladophyll" (= "Phyllode")

My questions:

1) What are the correct definitions of the terms "Phylloclade", "Phyllode", "Cladophyll" and "Cladode"?

2) Are the examples (provided in my notes and the Wikipedia articles) actually relevant/correct? For example: Does Ruscus possess Phylloclades (as suggested by the Wikipedia article) or does it possess Cladophylls (as suggested by my teacher)?

3) Building on question (1): Does "Phylloclade" = "Cladode", and "Cladophyll" = "Phyllode"?

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  • $\begingroup$ there seems to be a discrepancy in the term cladophyll in thiswebsite it is a modified leaf but in thiswebsite it is a modified stem. $\endgroup$
    – user 33690
    Oct 19, 2018 at 6:03
  • $\begingroup$ But my high school level textbook however claims cladophyll and cladode to be synonymous so it's a stem.. but the wiki page definitely says it's a leaf modification. This is ambiguous! $\endgroup$
    – user 33690
    Oct 19, 2018 at 6:10

2 Answers 2

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Apart from the discrepancy of the cladophyll term I can say that both your teacher and the wiki page are correct.

If you read the Wiki page carefully it states that

Phylloclades and cladodes are flattened, photosynthetic shoots, which are usually considered to be modified branches. The two terms are used either differently or interchangeably by different authors.

(As you have also quoted)

This is simple because both phylloclades and cladodes are stem modification for photosynthesis and xerophytic adaptation as well. So in this context they are interchangeable

Also if you have further read the article it states why the terms are interchangeable and why not. The different levels of definition are given:

Definitions of the terms "phylloclade" and "cladode" vary. All agree that they are flattened structures that are photosynthetic and resemble leaf-like branches. 

one definition, phylloclades are a subset of cladodes, namely those that greatly resemble or perform the function of leaves,[2] as in Butcher's broom (Ruscus aculeatus) as well as Phyllanthus and some Asparagus species.

The definition given by your teacher can be interpreted by these two definitions stated in the Wiki page:

By an alternative definition, cladodes are distinguished by their limited growth and that they involve only one or two internodes.[3] By this definition, some of the most leaf-like structures are cladodes, rather than phylloclades. By that definition, Phyllanthus has phylloclades, but Ruscus and Asparagus have cladodes.

Another definition uses "phylloclade" to refer a portion of a leaf-like stem or branch with multiple nodes and internodes, and "cladode" for a single internode of a phylloclade.

But phyllode is a leaf modification, specifically a modification of the petiole for photosynthesis and a xerophytic adaptation to some extent. (Source is the Wiki page itself)

So to conclude

  • phyllode is completely different from phylloclade and cladodes.

  • Taking the type of morphology of the plant into consideration and the definition used, phylloclade and cladodes may be used interchangeably or may not be.

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  • $\begingroup$ I will write an update if I find an answer to the discrepancy part $\endgroup$
    – user 33690
    Oct 19, 2018 at 6:51
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Just Remember the two main ; Phylloclade is a STEM modification for desert like area in which the stem becomes broad and fattened (in opuntia) or cylindrical(in euphorbia) !!

Phyllode is a LEAF modification and found in Australian Acasia in which the PETIOLE becomes a little braod and start performing photosynthesis!!

More key differences can be found on here https://www.differencebtw.com/difference-between-phyllode-and-phylloclade/

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