The genus Cinnamomum

Table 2.4 Stomatal characteristics of four species of Cinnamomum
Botany and Crop Improvement of Cinnamon and Cassia 31
Species Frequency/mm 2 Guard cell length Guard cell breadth
(mm) (mm)
C. verum (India) 609 0.018 0.016
C. verum (Sri Lanka) 637 0.017 0.015
C. verum (wild) 609 0.019 0.018
C. cassia 425 0.020 0.017
C. camphora 354 0.023 0.021
C. malabatrum (1) 637 0.016 0.017
C. malabatrum (2) 651 0.018 0.018
C. malabatrum (3) 623 0.018 0.017
C. malabatrum (4) 680 0.016 0.016
Source: Shylaja, 1984.
C. camphora and in C. cassia while C. verum and C. malabatrum have a higher frequency.
Guard cell dimensions do not show much variation among species except in C. camphora,
in which the dimensions are higher than those in other species.
Stomatogenesis
Metcalfe and Chalk (1950) and Kasapligal (1951) were of the opinion that stomata in
Lauraceae were paracytic (Rubiaceous), i.e. that they remain surrounded by two subsidiary
cells placed parallel to the pore. Pal (1974) reported that in C. camphora and
C. zeylanicum (C. verum) stomata were anomocytic, i.e. stomata were surrounded by a
number of epidermal cells that were not differentiated into subsidiary cells. Kostermans
(1957) and Avita and Inamdar (1981) were of the opinion that stomata in Cinnamomum
were paracytic. Shylaja (1984) confirmed anomocytic stomata in C. verum, C. cassia,
C. malabatrum, C. perrottettii, C. riparium, C. macrocarpum and paracytic stomata in
C. camphora.
The process of anomocytic stomatogenesis in C. verum was outlined by Pal (1978) and
Shylaja (1984). In young leaves, epidermal cells are regularly arranged, straight walled
and polygonal. Stomata differentiation initiates when leaves attain a length of 11–15
mm and a width of 5–8 mm. The development of stoma begins when an epidermal cell
differentiates into a protoderm cell by the formation of a septum that produces two
unequal cells (Fig. 2.7). The smaller cell is lenticular in shape, having a prominent
nucleus. This cell functions as the meristemoid, while the larger cell becomes a normal
epidermal cell. The meristemoid increases in size, becomes almost circular and divides
vertically to form two equal or sometimes unequal guard cells. These guard cells
enlarge and become kidney shaped, leaving a pore in the centre. As the leaf enlarges the
epidermal cell walls become sinuous in C. verum and in many other species. At this
stage four to five neighbouring cells of various shapes and sizes surround the guard
cells. The meristemoid directly acts as guard cell mother cell, and the neighbouring
cells are derived from other protoderm cells, hence the development is perigenous type.
Anomocytic stoma is generally regarded as the primitive type and occurs in the primitive
land plants such as Psilophytales. The paracytic type is also primitive, occurring
in Equisetales, but it is derived from the anomocytic type. In this genus different types
of stomata have been reported. Such developmental variations are common in any genus