Differences among the three races of tea plant
Anatomical features
The three different types of tea show some differences in their anatomical features and chemical composition. Like in many plant species, in tea leaves also sclereids, also known as stone cells, are developed. These are strongly thick walled cells where no living content is found in the cavity or lumen.The sclereids are deposed in the leaf lamina at the right angle to the mid rib.
In typical China tea plant, sclereids are either absent or very rarely present but these are present in large numbers in other two races. The few sclereids present in China plant are long and slender with smooth wall and a narrow lumen. However, there are differences in the morphology of the sclereids found in these two types of tea.The sclereids of Assam plant are short, upper end is acuminate the lumen is constricted at several points and have a few spicules i.e. out-growth. In plants of southern race, sclereids have a broad lumen without any constriction and these are covered by large number spicules.
Typical sclereids of (A) China (B) Assam and (C) Cambod plants
Upper ends of sclereids are pointing to upper leaf epidermis
In China plant, the palisade parenchyma usually consists of two layers of cells and occasionally three, whereas in Assam and Cambod plants one, rarely two, layers of palisade cells are present.
Chemical composition
In chemical composition also, the three types of tea plants have differences. Triglycosides of quercetin and kaempferol are found in the China tea plant and not in the other two kinds of tea. An unknown phenolic substance designated IC is found in Cambod tea and not in other two races.
Distinguishing anatomical and chemical characters of the three races of tea
| China | Assam | Cambod |
| Sclereids absent or rare | Sclereids numerous | Sclereids numerous |
| Sclereids slender almost without spicules | Sclereids stout with a few spicules | Sclereids stout with numerous spicules |
| Lumen of sclereids almost completely closed | Lumen of sclereids of irregular width, closed in places completely closed | Lumen of sclereids of irregular width, but not closed |
| Triglycosides present in fairly large amount | Triglycosides absent | Triglycosides absent |
| IC absent | IC absent | IC present in fairly large amount |