Question

What are raphides and where they are found?

Answer 1

Hint: Accumulation of raphides is most likely as a defense mechanism against herbivory. Raphides are found in specialized plant cells or crystal chambers called idioblasts.

Complete answer

>Raphides typically occur in parenchyma cells in aerial organs, especially the leaves, and are generally confined to the mesophyll cells. As leaf area increases, so does the number of raphides also increases. >A cell with an enlarged nucleus indicates the presence of these crystals.
>Raphides, needle-shaped calcium oxalate crystals, play a defensive role against herbivores.
>They are found in various tissues including leaves, roots, shoots, fruits etc.
>Raphides have defense mechanisms against plant predators. They have toxic which tear and harm the soft tissues of the throat of the plant predator chew on plant leaves. Raphides are commonly found in monocots families such as Araceae, Agaraceae, Orchidaceae etc. and also in Dicot families such as solanaceae, Rubiaceae etc. They are also found in many aquatic plants (eg. Pistia, Eicchornia etc.).
>Commonly eaten foods with raphides include spinach, pineapple, agave and kiwi fruit etc.
>Many functions have been attributed to calcium oxalate crystals in plants such as participating in calcium homeostasis, storage of calcium, removal of excess oxalate, metal detoxification, tissue support and protection against insects and grazing animals.
>They are found in more than 200 families of plants.

Note:Defensive role of raphides was firstly observed by a German scientist Ernst Stahl. He observed that snails avoided eating plant material containing raphides, but once plant material was treated by acid to dissolve the calcium oxalate, snails consumed treated plant material.