According to the classic description of the development of rice
(Itoh et al., 2005), the adult rice leaf is strap-like and divided into three
distinct regions along the proximal-distal axis and is also polarized along the
adaxial-abaxial axis. The leaf sheath forms the proximal region and surrounds
the shoot apex. The young rice leaves are enclosed in the sheaths of the older
leaves, protecting them from physiological and physical damage. The major
site of photosynthesis is blade or lamina in the distal part of the leaf. Between
the blade and the sheath is the boundary that consists of the three distinct
parts. Firstly, the lamina joint or collar is a whitish region located in the base of
the blade. The collar is responsible for bending the leaf blade toward the
abaxial side. Secondly, the ligule, which is usually differentiated into two
segments in mature leaves, is membranous. The other part, positioned at the
leaf margins, are the auricles which are a pair of small appendages containing
long hairs, as shown in Figure 1.2. Over the epidermis layer of the entire rice
leaf surface, except for the adaxial surface of the sheath, there are numerous
papilla and trichomes.