The genus Cinnamomum

Other tissue culture studies
Botany and Crop Improvement of Cinnamon and Cassia 65
Yazaki and Okuda (1993) discussed the production of condensed tannins in tissue
culture of C. cassia. They induced callus from petiole explants cultured in Linsmaier and
Skoog’s (LS) agar medium containing several combinations of growth regulators (1965).
Callus tissues induced from petiole segments were further grown on LS medium containing
10 5 m IAA and 10 5 m 6-benzyl adenine as well as on a medium containing
10 4 m NAA and 10 6 m BA. Callus was further subcultured with 0.2% gellan gum
at 25 °C in the dark. The clumps of callus tissues developed on HPLC analysis were
found to contain epicatechin, procyanin B 2, procyanidin B 4, and procyanidin C 1, which
are precursors of condensed tannins. The vanillin-HCL test showed the occurrence of
a large amount of high-molecular condensed tannin in the callus cultures.
Physiological studies
Little is known about the physiology of cinnamon. Pathiratna et al. (1998) studied the
shade effects on photosynthesis of cinnamon plants grown under four levels of growth
irradiances ranging from 12% to 100% daylight. Photosynthetic rate at light saturation
derived from the data fitted to a quadratic model showed an increase from
5.14 to 7.25 mol m 2 s 1 . Light required for 50% light saturation of photosynthesis
also increased with the increase of growth irradiance. The above authors found that
light compensation point and dark respiration derived by fitting the data from 0 to
81 mol m 2 s 1 photon flux density to a linear model, and dark respiration measured
directly increased with the increase of growth irradiance. The plants under 12% daylight
had the highest quantum efficiency. The percentage increase of photosynthetic
rate from growth irradiance to that at light saturation was greatest at 12% daylight.
The size of leaves, the leaf area per unit, fresh and dry weight of leaves and leaf area per
unit dry weight of plants decreased with the increase in growth irradiance. These
results also indicated the C 3 nature of photosynthesis and the characteristics of shade
adapted photosynthesis in cinnamon.
In another study Pathiratna and Perera (1998) reported the growth and bark yield of
cinnamon grown under the shade of rubber trees, having an incident solar radiation of
1170 mol m 2 s 1 . The major yield components of bark yield (number of shoots per
bush and mature shoot length) were highest in cinnamon bushes under 21% daylight.
Bark thickness and average shoot diametre were higher under 100% and 53% daylight
but significantly lower under 21% and 5% daylight. Bark yield per bush in plants
under 21% daylight was significantly higher than under other light levels. Those under
5% daylight gave the lowest bark yield per bush and were on par with 100% and 53%
daylight.
Bregvadze (1975) reported that frost resistance in Cinnamomum species is related to
the degree of growth inhibitor activity in leaves; the greater the activity, the greater the
resistance to frost. Thus selection for a high degree of growth inhibitor activity to
increase frost resistance is possible.
Menon et al. (1993) used linear measurements for calculating leaf area. The model
Y aL B (0.72 L B) had given an R 2 value of 0.98, indicating that 98% of the
variance in leaf area could be explained by this model. The computed leaf area was in
close agreement with the actual area based on measurement.