the sago palm tolerates up to 171 mM (1.0%) NaCl concentration for at least 30 days.
While the sago palm seedlings treated with NaCl, the dense distribution of Na was
observed around the endodermis of the large roots based on an X-ray microanalysis
(Ehara et al. 2008a). The effect of increased Na
+ concentration in the seedlings
relevant to Ca
2+ and Mg
2+ distribution to the leaflets was small (seedlings were at the
eighth leaf stage, treated with 342 mM (2%) NaCl). Notwithstanding the remarkable
decrease in the transpiration rate and slight delay in the emergence of new leaves
during the NaCl treatment, there was no significant difference in dry matter weight of
the leaflets and petioles at each leaf position. It was, therefore, considered that salt
resistance of sago palm might be due to salt avoidance aiming at mechanically
preventing the excessive Na distribution within the plant tissue and maintaining the
water status in the leaves by restricting the transpiration.
Sago palm properties such as salinity resistance are important to consider when
expanding the cultivation areas and to avoid competition with other crops (Sato
1993). Shimoda and Power (1990) reported that the environment of sago palm
growing area is very diverse, including both brackish water and fresh water areas.
The ability of sago palm to grow in lowland swamps affected by seawater suggests
that it possesses an extent of salinity resistance. Genus Metroxylon is generally found
growing behind mangroves belonging to the genera Rhizophora and Bruguiera or
nipa palms (Nypa fruticans) (Ehara et al. 2008b). Sago palm is considered to possess
some avoidance mechanisms to control the translocation of sodium ions to the
leaflets and keep the leaflet sodium concentration low by storing sodium in the
roots and petioles as described in the above section. In many crop species, when they
absorb excessive amounts of sodium, the absorption of potassium will be depressed.
However, in the case of sago palms, the absorption of potassium and its translocation
can be maintained even under salt stress; such absorption tends to increase. As the
leaf blade potassium concentration tends to increase in sago palms under salt stress
(Ehara et al. 2008a), potassium appears to be an osmotic regulator, albeit of a lesser
extent than that in the coconut palm. This suggests that sodium exclusion is also
performed at a part of the endodermis in the genus Metroxylon (Naito and Ehara
2015).
17.5.2 Nutrient Characteristics for Growth
Kueh (1995) tested fertilizer application from the time of sago palm planted in a
thick peat soil layer (>1.5 m) in Sarawak, Malaysia. The chemicals, i.e. 0.42 kg N/
plant/year of N (ammonium sulfate), 0.36 kg P 2 O 5 /plant/year of P (phosphate rock),
and 1.2 kg K 2 O/plant/year of K (potassium chloride), were applied and their effects
on sago palms (1 to 12-year-old) for 12 years were the consistent number of leaves
from the second to sixth year, trunk diameter from the seventh to eighth year, and
trunk height from the seventh to tenth year. Moreover, N application had no effect on
the N content in the leaf during the experiment and the application of P and K
affected the leaf P and K contents for some years.
496
H. Ehara et al.
While the sago palm seedlings treated with NaCl, the dense distribution of Na was
observed around the endodermis of the large roots based on an X-ray microanalysis
(Ehara et al. 2008a). The effect of increased Na
+ concentration in the seedlings
relevant to Ca
2+ and Mg
2+ distribution to the leaflets was small (seedlings were at the
eighth leaf stage, treated with 342 mM (2%) NaCl). Notwithstanding the remarkable
decrease in the transpiration rate and slight delay in the emergence of new leaves
during the NaCl treatment, there was no significant difference in dry matter weight of
the leaflets and petioles at each leaf position. It was, therefore, considered that salt
resistance of sago palm might be due to salt avoidance aiming at mechanically
preventing the excessive Na distribution within the plant tissue and maintaining the
water status in the leaves by restricting the transpiration.
Sago palm properties such as salinity resistance are important to consider when
expanding the cultivation areas and to avoid competition with other crops (Sato
1993). Shimoda and Power (1990) reported that the environment of sago palm
growing area is very diverse, including both brackish water and fresh water areas.
The ability of sago palm to grow in lowland swamps affected by seawater suggests
that it possesses an extent of salinity resistance. Genus Metroxylon is generally found
growing behind mangroves belonging to the genera Rhizophora and Bruguiera or
nipa palms (Nypa fruticans) (Ehara et al. 2008b). Sago palm is considered to possess
some avoidance mechanisms to control the translocation of sodium ions to the
leaflets and keep the leaflet sodium concentration low by storing sodium in the
roots and petioles as described in the above section. In many crop species, when they
absorb excessive amounts of sodium, the absorption of potassium will be depressed.
However, in the case of sago palms, the absorption of potassium and its translocation
can be maintained even under salt stress; such absorption tends to increase. As the
leaf blade potassium concentration tends to increase in sago palms under salt stress
(Ehara et al. 2008a), potassium appears to be an osmotic regulator, albeit of a lesser
extent than that in the coconut palm. This suggests that sodium exclusion is also
performed at a part of the endodermis in the genus Metroxylon (Naito and Ehara
2015).
17.5.2 Nutrient Characteristics for Growth
Kueh (1995) tested fertilizer application from the time of sago palm planted in a
thick peat soil layer (>1.5 m) in Sarawak, Malaysia. The chemicals, i.e. 0.42 kg N/
plant/year of N (ammonium sulfate), 0.36 kg P 2 O 5 /plant/year of P (phosphate rock),
and 1.2 kg K 2 O/plant/year of K (potassium chloride), were applied and their effects
on sago palms (1 to 12-year-old) for 12 years were the consistent number of leaves
from the second to sixth year, trunk diameter from the seventh to eighth year, and
trunk height from the seventh to tenth year. Moreover, N application had no effect on
the N content in the leaf during the experiment and the application of P and K
affected the leaf P and K contents for some years.
496
H. Ehara et al.