OD mR HIELD GLASS 6 Calcium oxalate is an insoluble precipit

OD mR. HIELD GLASS 6 Calcium oxalate is an insoluble precipitate of oxalic acid, which is a strong metabolic toxin. Briefly explain the function or importance of the crystals seen in a zebrina. (20) 7 some plants, for example the jackin-the-pulpit, have high concentrations of calcium oxalate crystals in their cells. Taking a bite of the raw plant tissue produces a severe burning sensation in the lining of the mouth. Drinking water does not alleviate the pain. Can you suggest a reason why drinking water does not help? (21) 8 How do the druses seen in a begonia differ in appearance from the raphides seen in a zebrina? (22) a. Begonia: b. Zebrina: Exercises for the Botany Laboratory

Solution

Zebrina is a species of spiderworts, usually belonging to the the genus Commelinaceae. They have big vacoules, and also show the presence of ertain mineral structures of plants. In Zebrina, vacuoles contain long needle-like crystals of calcium oxalate, called raphides, which are easily identified using a microscope. Raphides are rarely found as a single crystal, rather they are usually found as a bunch of crystals.

Raphides have a sharp end, which on consumption, release a toxin that is harmful to a plant\'s predator.Stinging and burning can occur in the mouth of a predator who has eaten a raphide crystal, and esophageal damage can occur. A lethal dose of raphide crystal to an animal like a field mouse is 15 mg/kg.

Biochemical pathways involved in crystal formation include hydrolysis of oxaloacetate, glycolate/glyoxylate oxidation or oxidation cleavage of L-ascorbic acid.