The change in leaf thickness is highly correlated with the thickness of palisade tissue.
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.
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;
