There are 2-3 layers of long-column-shaped palisade tissue under the upper epidermis, and there are a great number of mechanical tissues which made up of vascular bundle sheath .
The upper epidermis, palisade tissues and leaves are all thinner, so the leaves are more tender, and its yield is 8% higher;
The mesophyll is not differentiated into spongy and palisade tissues, but mesophyll near midrib in tip and middle parts of leaf is often lengthened to appear as palisade-liked tissue.
The change in leaf thickness is highly correlated with the thickness of palisade tissue.