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Starch - Starch is the major energy storage material of trees. Starch is not soluble in water. Trees only store starch in living parenchyma cells. Basically trees do three things, they load (sunlight energy, water, elements), they store and then they use. Trees change glucose to starch and store starch in living parenchyma cells. Then when trees need energy (see "Energy") the starch is transformed back to glucose. Glucose is soluble in water, but starch is not. Starch is the savings account for the tree (symplast). Starch = biological currency in storage. The difference between starch and glucose is a water molecule. An enzyme called amylase can change the starch chains back to glucose molecules. Trees store an abundance of starch in woody roots. Starch is stored behind buds during the end of the growing season. The current developing growth increment does not store starch until the end of the growth period. Storage of compounds for new growth and defense is usually as insoluble starch or as oils and fats. Starch is made up of long chains of glucose. Starch is different from cellulose because of a different type of bonding. Starch-is an insoluble polysaccharide. It is made up of two glucose polymers, amylose and amylopectin. The glucose units are connected by 1-4 alpha linkages. Cellulose is connected by 1-4 beta linkages which causes the long molecule chain to twist.
Starch grains can be stained purple with a 2% solution of iodine in potassium iodide (I2KI). See page 277 in the book MODERN ARBORICULTURE by SHIGO for info on I2KI. Picture is a Tilia (Linden). You can see the purple in this stained sample.