Jpn. J. Trop. Agr. 51(4) : 160-168, 2007

Na+ and K+ Concentrations in Different Parts and Physiological Features of Becc. under Salt Stress

Hiroshi EHARA1*, Hiroyuki SHIBATA1, Hitoshi NAIT02, Takashi MIsHIMAI and Philimon ALA3

1 Graduate School of Bioresources , Mie University 2 College of Life Science , Kurashiki University of Science and The Arts 3 Department of Forests ,

Abstract Na+ and K+ concentrations in different plant parts and some physiological features under NaCl solution treatment were investigated to study the absorption and distribution of Na+ and K+ in Metroxylon warburgii (Heim) Becc. that belongs to same with sago palm (M, sagu Rottb.) in the palm family. Seedlings at the 11th or 13th stage were used for the treatment of 342mM (2%) NaCl in a green house under natural sun light in mid summer in central Japan. M. warburgii maintained a low Na+ concentration in the leaflets of upper active by storing Na+ mainly in the petioles at lower leaf positions under the NaCl treatment for 36 days. The Na+ concentrations in the roots were lower in the steles than in cortices, and this result suggests the existence of a mechanism to restrict the over influx of Na+ from the cortex into the stele of the roots. The K+ distribution to the leaflets was not affected by the change in the Na+ concentration in the roots and petioles in M warubrugii. Photosynthetic rate decreased with the NaCl treatment, which was attributed to decrease in stomatal conductance and chlorophyll content per unit leaf area. Key Words: Metroxylonpalm, NaCl treatment, photosynthetic rate, salt avoidance, stomatal conductance, transpiration rate

banana and taro (Barrau,1959; Takamura, 1990). Sago Introduction palm is still important as a staple food in some areas of The genus Metroxylon in the palm family spreads Southeast Asia and in the other areas inhabited by from Southeast Asia to Melanesia, Micronesia and M•¬lanesian people (Ehara et al., 2000). Sago palm is

Polynesia is divisible into two sections, that is, sections one of the most important crops not only for Metroxylon (Eumetroxylon) and Coelococcus (Beccari, subsistence economy but also for rural development in

1918; Rauwerdink, 1986). M. sagu Rottb. that is only swampy areas of the tropics because its carbohydrate of section Metroxylon (Eumetroxylon: although (sago starch) can be further processed into various monophyly of this section remains uncertain) is basic raw materials for commercial food, animal feed distributed in Southeast Asia: Thailand, Malaysia, and for industrial uses. Contrarily, in recent decades

Indonesia, the Philippines, and the northwestern the sago (palm starch) of the other Metroxylon spcecies

Melanesia: Papua and the Solomons. Five in section Coelococcus have been used as an emergency species are recognised within section Coelococcus that food when major crops such as taro or yam have been represents the eastern half of the distribution of the damaged by cyclone or the other hazards (Ehara et al., genus Metroxylon: one species in Micronesia and the 2003a) . The most important contemporary use of other four species in Melanesia and Polynesia, from Metroxylon palms is as materials for housing materials the Solomons to and (McClatchey, 1999). in Melanesia and Micronesia. Sago palm (M. sagu Rottb.) that is distributed in Since sago palm is distributed and can grow in

Southeast Asia and in areas inhabited by Melanesian brackish water areas near the coast, it is considered to people grows in swampy, alluvial and peaty soils where be salt-resistant (Yamamoto,1996) . Sago palm maintains almost no other crops can grow without drainage or a low Na+ concentration in the leaflets, which may be

soil improvement (Flack, 1977; Sato et al., 1979; Jong, attributed to high Na+ storage capacity in roots under

1995) . This palm species stores a large amount of NaCl treatment (Ehara et al., 2006). We found that K+

starch in the trunk, approximately 300kg (dry wt.) per absorption and distribution to the leaflets are not palm (Ehara, 2006) and has long been utilized like affected though the changes in Na+ concentrations in Received Jan. 22, 2007 the roots and petioles were observed under the Accepted Sept. 22, 2007 treatment. M warburgii (Heim) Becc. is one of * Corresponding author Coleococcus palms and is distributed in Vanuatu, Fiji Kuriimamachiya-cho, Tsu 514-8507, Japan [email protected] and Samoa (McClatchey, 1999). Genetic distance Ehara et al.: Response of Metroxylon warburgii to Salt Stress 161

between this species and sago palm is considered to be fertiliser (N:P205:K20 = 12:12:12) was applied at the same level with that between sago palm and M rate of 0.3g each per pot. The pots were placed in a amicarum (H. Wendl.) Becc. distributed in Micronesia, green house under natural sun light (maintained at but not as close as that between sago palm and M. over 10 •Ž even in mid winter) at Mie University salomonense (Warb.) Becc. distributed in the Salomon located in central Japan. Seedlings at the 11th leaf

Islands and Vanuatu (Ehara, 2006). Plant size of adult stage (the 12th leaf was emerging) were transferred palm is small and dry matter percentage and starch one each to a 1/5000a Wagner pot filled with paddy soil concentration in pith at maturity are low in M warurgii and were cultivated in the same ways as germinated compared with sago palm (Ehara, 2006; Ehara et al., . The compound fertiliser was applied at the rate

2003b). Contrarily, total sugar concentration in pith of of 0.8g each per pot.

M. warburgii is comparatively high (Ehara et al., Three seedlings at the 11th leaf stage (the 12th

2003b). Sago (palm starch) from M. warburgii had leaf was emerging: mean plant length was 60cm) were been used until the 1950s at least on Gaua in Vanuatu used each for NaCl treatments in addition to three

(Ehara et al., 2003a) . Recently the Vanuatun Government other seedlings, two at the 11th leaf stage and one at recognises the importance of M warburgii as 13th leaf stage, as controls. Water containing 342mM thatching material and recommends to cultivate it NaCl (corresponding to 2% NaCl) was used in the NaCl

(Ehara et al., 2003a) . Furthermore, the new industries treatments and 200m1 of water with or without NaCl such as natangra (one of vernacular names of was supplied by turns every other day from 1 July to 6

Metroxylon palms in Vanuatu) jewellery using Met roxylon August 2003. NaCl concentration of the treatment seeds and collecting the seeds for the nurseries are solution was decided considering the previous result expected to increase employment opportunities. Though that sago palm (M sagu) at the 8th leaf stage survived there are some reports on the biology and agronomic under 342mM NaCl treatment for 30 days (Ehara et al., features of Metroxylon palms growing in Vanuatu and 2006). the surrounding area (Dowe, 1989; Dowe and Cabalion, The pots were plugged before supplying the NaCl

1996; Ehara et al., 2003b; McClatchey,1999; Rauwerdink, solution and the plug was pulled after the one day to

1986), only few studies on the physiological characteristics drain the solution. Subsequently the pots were of M warburgii exist. Growth environment of M plugged and 400m1 of water without NaCl was supplied warburgii, for instance in Vanuatu and Fiji is similar to and kept for one hour and then drained. After that the that of sago palm as swampy area to where brackish other 400ml of water without NaCl was supplied again water flows in, therefore M. warburgii is considered to and kept for one day and then drained. This process is be salt-resistant as well as sago palm. Thus, we indispensable to avoid excess NaCl accumulation over investigated the Na+ and K+ concentrations in different assumed concentration and was repeated for 36 days. plant parts and some physiological features under In the controls, water without NaCl was used and same

NaCltreatment to study the absorption and distribution amount of water was supplied with same procedure in of Na+ and K+ in M warburgii and discussed the the NaCl treatments. similarities and differences between this species and

M. sagu studied in the previous report. Transpiration and photosynthesis

The amount of transpiration of each plant per day Materials and Methods was measured by weighing the whole pot including the

Plant materials and NaCl treatment plant, culture medium and water. Each pot was tightly

Fruits were collected from Espritu Santo in sealed with a plastic sheet during the measurement of

Vanuatu in the middle of September 2002. Fertilised the amount of transpiration. On 28th July 2003 (27 days and well-developed were selected and were from start of the NaCl treatment), net photosynthetic treated physically to remove coat tissues. The rate (Pn) and stomatal conductance (Cs) of the 2nd cleaned seeds were put one each in a plastic beaker leaf from the top among the fully expanded leaves (the filled with 100ml water and the beakers were placed in 12th or 13th leaf in the control , the 11th leaf in a dark air-conditioned room at 30 •Ž, as described in the treated plants) were measured by a portable previous reports (Ehara et al., 1998; 2001; 2006) . The photosynthetic meter (Koito CIRAS-1, Japan) under germinated seeds were transplanted one each to a different conditions of photosynthetically active radiation plastic pot (1.5L) filled with paddy soil. Compound (PAR) that were set using cheesecloth. After being 162 Jpn. J. Trop. Agr. 51(4) 2007 subjected to the NaCl treatment for 35 days, a portion A statistical analysis was performed by NCSS 2001

(middle part of right and left half leaflet blades of the (Number Cruncher Statistical Systems) mid-leaflet) of the leaves that were used for . Results and Discussion measurement of photosynthetic rate was used for measurement of chlorophyll concentration by the New leaves emerged from both control and procedure of Mackinney (1941). Five leaflet disks treated plants during the NaCl treatment, however,

(diameter of 0.25cm2) were punched out from each of emergence of the 14th leaf in treated plants slightly right and left half leaflets and were used for delayed compared with that in two of the control chlorophyll extraction with 80% acetone. plants. The number of leaves dead during the experiment was one in the control plants. Contrarily, Na+ and K+ concentrations in plant two leaves from the bottom in the treated plants were

The treated and control plants were sampled and dead during the NaCl treatment, and leaflets became were washed in distilled water. The plants were pale colour even at middle and higher leaf position. separated into three parts, leaflets, petioles (including There was no significant difference in change in plant rachis: petioles hereafter) and roots, and the roots length between the control and treated plants during were divided into small roots, stele and cortex (with the treatment (Fig. 1). Fig. 2 shows dry matter weight epidermis, exodermis, suberized sclerenchyma cells: of the control and treated plants at the end of the NaCl cortex hereafter) of large roots according to Nitta et al. treatment. There was a variation in dry matter weight

(2002) : large roots about 6 to 11 mm in diameter; small among the control plants because of their variation in roots less than 6 mm in diameter. The separated plant age. In case of comparison between the control samples were dried at 80•Ž and ground into a powder and treated plants that were same leaf age at the start and were reduced to ash for sodium and potassium of the NaCl treatment, the difference was relatively extraction with distilled water. The Na+ and K+ large in the leaflet dry weight (Table 1). This result concentrations in the leaflets and petioles at each leaf was attributed to delay of the leaf emergence with the position, and in the roots were determined using an ion NaCl treatment. In case of sago palm (M. sagu), there chromatograph with a conductivity detector (Shimazu was no differences in the appearance between the

CDD-6A, IC-C2, Japan). treatments consisting of 86mM (0.5%) to 342mM (2%)

Fig. 1 Change in plant length during the NaCl treatment. Fig. 2 Dry matter weight of different plant parts at the end Open and closed symbols indicate the control (C1- of the NaCl treatment. C3) and treated plants (Ti - T3), respectively.

Table 1 Comparison of dry matter weight of the control and treated plants that were same leaf age at the start of the NaCl treatment

Data are the mean value of two plants (control) and mean value with standard deviation of three plants (treatment). Ehara et al.: Response of Metroxylon warburgii to Salt Stress 163

NaCl and the absence of NaCl in the culture solution, matured leaves of M warburgii show a markedly for 30 days (Ehara et al., 2006). Although ages of different leaflet surface from the other Metroxylon plant, the atmospheric condition and duration of the species concerned with the difference in cuticular treatment of the current experiment were different development (Ehara et al., 2003b). Well developed from those of the previous experiment, the effect of cuticular layer is observed on the matured leaflet in

NaCl treatment on the growth characteristics seems to this species (Naito et al., 2006). Although we did not be different between M warburgii and M sago. measure the transpiration rate at different leaf position, the expanding leaf might perform still relatively higher

Na+ and K+ concentrations in different plant parts transpiration in the plants used. This may be one of

Roots, leaflets and petioles at different leaf positions the reasons why the Na+ concentration of the 13th leaf

Fig. 3 shows the Na+ concentrations in the in the treated plants was higher than that the control leaflets, petioles and roots. The Na+ concentration in plants. The difference in the Na+ concentration in the the roots of the treated plants was 162ƒÊ molg-1 and was leaflets between the control and treated plants was higher than that of the control plants. In the , large at lower leaf positions but small at higher leaf the Na+ concentration ranged from 315 to 747ƒÊ mol g 1 positions except expanding leaf. In the leaflets of the in the treated plants, the values of which were tended 10th, 11th and 12th leaves, there was no significant to be higher at lower leaf positions than at higher leaf difference in the Na+ concentration between the positions. The Na+ concentration in the petiole of the control and treated plants. The 12th leaf was uppermost treated plants was significantly high at all the leaf fully expanded leaf, therefore it can be said that the positions compared with the control plants. On the change in Na+ concentration in leaflets was very small other hand, the Na+ concentration in the leaflets in most active three leaves. ranged from 16 to 134ƒÊl g-1 in the treated plants, As described above, the Na+ concentration in the the tendency of difference in the values of which at roots clearly increased by the NaCl treatment, and that different leaf positions were almost same with that in in the petioles increased by the NaCl treatment at all the petioles of the treated plants except the expanding the leaf positions and the increments tended to be

13th leaf. Generally, the expanding leaf is under higher at lower leaf positions than at higher leaf growing process especially in secretion and/or positions. The tendencies of increase in Na+ accumulation of the external cuticular, which will lead concentrations in the roots and petioles in M higher cuticular transpiration amount. In fact, the warburgii were similar with those in sago palm (Ehara et al., 2006). The extent of increase in Na+ concentration with the NaCl treatment was higher in the petioles than in the roots in M. warburgii, however, this result was opposite from the case in sago palm (Ehara et al., 2006). Consequently, there may be inter specific difference in capacity to store Na+ in the roots considering the differences in increases of Na+ concentrations in the roots and petioles between M. waruburgii and sago palm. In the leaflets, the Na+ concentration was clearly increased by the NaCl treatment at lower leaf positions in M waruburgii, which was different from sago palm. In case of sago palm, the Na+ concentration in the leaflets did not increase not only at higher leaf positions but also at Fig. 3 Na+ concentration in roots, leaflets and petioles at lower leaf position. Sago palm maintains a low Na+ different leaf positions under NaCl treatment. White and black bars indicate leaflet and petiole, concentration in the leaflets, which may be attributed respectively. Horizontal lines indicate the standard mainly to Na+ storage mechanism in roots under NaCl deviation (n=3; data of the 16th leaf and 15 the leaf treatment (Ehara et al., 2006). The difference in the was from one and two plants, respectively) . Asterisks effect of NaCl treatment on the Na+ concentration in indicate significant difference between the control and treated plants at the 0.05 probability level, the leaflets between M warburgii and sago palm may according to the T -test. be concerned with their different Na+ storing capacity, 164 Jpn. J. Trop. Agr. 51(4) 2007

particularly in the roots of each species. leaflets was not affected by the change in the Na+ The K+ concentration in the roots was 88ƒÊl mol g-1 concentration in the roots and petioles, which suggest and 1151 mol g 1 in the control and treated plants, the importance of K+ accumulation to maintain a respectively, and in the petioles the concentration favourable physiological status or in M warubrugii as ranged from 23 to 347ƒÊ mol g-1 and 13 to 236ƒÊ mol g-1 well. and in the leaflets from 19 to 234ƒÊmol g-1 and 13 to 276

ƒÊ mol g-1, respectively (Fig. 4). In the petiole and Different parts of roots leaflets, the K+ concentration tended to be higher at Two types of roots are distinguished in root higher leaf positions than at lower leaf positions in both systems of sago plam (Nitta et al., 2002). In M the control and treated plants. The K+ concentration in waruburgii also, the roots can be classified into two each part of the treated plants was almost same level types, large and small roots. Thus we investigated the compared with that of the control plants, that is, the Na+ concentration in both types of roots. The Na+ change in the K+ concentration in all the parts with the concentration in different parts of the roots is shown in

NaCI treatment was negligible. In the leaflets of Fig. 5. In the control plants, the Na+ concentration in lowermost two leaves (6th and 7th leaves) and the the cortices of the large roots was high compared with

petiole of lowermost three leaves (6th, 7th and 8th that in the steles of the large roots and in the small leaves), the K+ concentrations tended to be lower in roots, though the difference was not so large. The Na+ the treated plants than in the control plants, though the concentration in the roots of the treated plants was differences were still not significant because of their higher than that of the control plants in all the parts. In variations among the individuals. In all the parts, the K+ the treated plants, the Na+ concentration was clearly

concentration was low in M. warburgii compared with higher in the cortices of the large roots than in the

that in sago palm, which ranged from 558 to 563 mol steles and the small roots. The result, Na+ concentration

g-1 in the roots, 614 to 665ƒÊ mol g-1 in the petioles and in the steles is lower compared with the cortices in the

205 to 256ƒÊ mol g-1 in the leaflets (Ehara et al., 2006). treated plants, suggests that there should be a

As a whole, the pattern of differences in the K+ mechanism to restrict the influx of Na+ from the cortex

concentration in the petiole and leaflets at different leaf into the stele.

position of M warubrgii in the current experiment is Fig. 6 shows the K+ concentration in different almost same to that of sago palm reported in the parts of the roots. The K+ concentration was highest

previous paper. Our previous result suggested that K+ in the cortices of the large roots followed by the steles accumulation may be associated with osmotic adjustment and the small roots in both the control and treated in sago palm under salt stress. Yoneta et al. (2006) also plants. According to Nitta et al. (2002), large roots are

reported K+ was accumulated in leaflets through the

roots systems in response to NaCI stress in sago palm.

In the current experiment, the K+ distribution to the

Fig. 5 Na+ concentration in different parts of roots under NaCI treatment. Vertical lines indicate the standard deviation. Different letters in the figure indicate significant differences at different parts within the control or treated plants at the 0.05 probability level, according to the Tukey-Kramer test. Asterisks Fig. 4 K+ concentration in roots, leaflets and petioles at indicate significant difference in each part between different leaf positions under NaCI treatment. Bars the control and treated plants at the 0.05 probability and symbols are the same as those in Fig. 3. level, according to the T -test. Ehara et al.: Response of Metroxylon warburgii to Salt Stress 165

concentrations in the petioles and leaflets of lowermost two or three leaves. In some species, plant growth is not affected when the K+ concentration in plant is maintained even under NaCltreatment (Greenway, 1962a,; 1962b; Greenway et al., 1965; Munns et al., 1983; Jeschke et al., 1985; Yeo and Flowers, 1986) . The K+ concentrations in the top part did not decrease regardless of the leaf position in M warburgii at least in the active leaves except lowermost two or three leaves in the current experiment. It appears that Na+ absorption clearly did Fig. 6 K+ concentration in different parts of roots under not depress K+ absorption and distribution to the NaCltreatment. Vertical lines indicate the standard leaves in M warburgii even under the 342mM NaCl deviation. Letters and asterisks in the figure are the same as those in Fig. 5. treatment as well as sago palm in the previous paper (Ehara et al., 2006). Although new leaf emergence delayed slightly and leaf senescence of lower leaf adventitious roots whose primordial are formed just advanced with the NaCl treatment, M warburgii well inside the epidermis in the stem, emerged from the survived for 36 days in the current experiment. Our stem surface and grow downward into soil, and small previous and current results in sago palm and M roots are lateral roots whose primordial are formed on warburgii support the precede assumption by that salt large roots or on the other small roots, grow not only tolerance is related to the exclusion of K+ by Na+ downward and obliquely but also right above in soil. absorption in the leaf blade (Greenway, 1962a; 1962b; They reported that both large and small roots have the Munns et al., 1983; Jeschke et al., 1985; Yeo and same internal structures containing epidermis, exodermis, Flowers, 1986). K+ accumulation may be associated suberized sclerenchyma cells, cortex and stele, with with osmotic adjustment also in this palm species. only differences in their size or cell numbers. The functions and roles of large and small roots seem to be Physiological features different as follows: large roots seem to be a suitable Transpiration rate structure for air conduction and transport of nutrition The current experiment was conducted under and water; the internal structure of small roots is natural sunlight, therefore transpiration per plant suitable for air exchange and this root body is exposed varied daily because of the changing atmospheric in the air, the function of this roots seems mainly to be condition for each day. Thus the amount of transpiration air transportation from the root to the shoot rather per unit time is shown as five days moving average in than transport of nutrition or water (Nitta et al., 2002). Fig. 7. The treated plants started to decrease the Our current results of the K+ concentration that was higher in the large roots than in the small roots may show their functional difference such as in nutrient transport. There was no significant difference in the K+ concentration in the cortices of the large roots and in the small roots between the control and treated plants. Contrarily in the steles of the large roots, the K+ concentration was lower in the treated plants than in the control plants. Although there were no significant differences, the K+ concentrations in the petiole of lowermost two leaves and the leaflets of lowermost three leaves were tended to be lower in the treated Fig. 7 Change in transpiration rate under NaCl treatment. Open and closed symbols indicate the control and plants than in the control plants (Fig. 4). The low K+ treated plants, respectively. Data are the mean concentration in the steles of the large roots in the value with standard deviation of five days moving treated plants might account for the results of the K+ average (n=3). 166 Jpn. J. Trop. Agr. 51(4) 2007

transpiration rate after the 2nd day and it was less than treated plants under different PAR conditions. The

50% of the control plants after the 14h day. After that difference in the Pn between the control and treated

the transpiration rate increased in the control plants plants was small under lowest PAR, 150 mol m-2 s -1, and was stable at lower level in the treated plants. and it was greater under the higher PAR conditions.

Though the transpiration rate was decreased 35% with The Pn values in the treated plants were nearly half of

342mM NaCl treatment in sago palm (Ehara et al., the control plants at 300 to 1500ƒÊ mol m-2 s-1 PAR. The

2006). The tendency in the effect of NaCl treatment on Cs in the treated plants was comparatively smaller than

transpiration rate of M warburgii in the current that in the control plants at 300, 600, 1200 and 1500ƒÊ mol

experiment was same as that of sago palm, the extent m-2 s-1 PAR, and the values of the treated plants were

of decrease in transpiration rate was considered to be less than 50% of the control plants. The extent of

large in M warburugii compared with sago palm. decrease in Pn with the NaCl treatment was almost

same level with that in Cs. The cause of the decrease

Chlorophyll content per unit leaf area and photosyn- in Pn could be primarily attributed to the decrease in

thetic rate Cs, though the decrease in chlorophyll content per unit

The chlorophyll content per unit leaf area was 30 leaf area also might be one of the major factors limiting

ƒÊg cm-2 in the control plants and decreased to 20ƒÊg Pn. Considering the remarkable decrease in transpiration

cm-2, two-thirds of the control plants with the NaCl rate with the NaCl treatment, the decrease in Pn can

treatment. As described above, the leaflet colour in the be understood as a result of trade off for maintaining

treated plants was pale even at middle and higher leaf water status in plant body by restricting the transpiration

position, that was attributed to decrease of the rate to avoid water loss. Naito et al. (1994) reported chlorophyll content with the NaCl treatment. that it was important to maintain a high transpiration

Fig. 8 shows the Pn and Cs of the control and rate for exclusion of Na and growth under saline

conditions in rice seedlings. Our understanding of

restricting the transpiration under salt stress in M

warburgii was not in agreement with that in rice plant

reported as above by Naito et al. (1994). However, the

NaCl treatment for M warburgii in the current

experiment was much severe in its concentration than

that for rice seedlings (100mM NaCl for 12hours)

conducted by Naito et al., (1994). Plant salinity

resistance has been described as having components

of either avoidance or tolerance (Levitt,1980), that is to

say, salt resistance is the reaction to salt stress and

involves either salt tolerance or salt avoidance. According

to Johnson (1991), avoidance occurs when the plants

are able, at least in part, to exclude toxic ions from

internal plant tissue, and tolerance is exhibited by

plants that take up salt ions while showing a relatively

low level of tissue ion toxicity. As general strategies,

salt tolerance involves physiological and biochemical

adaptations for maintaining protoplasmic viability as

cells accumulate electrolytes, and salt avoidance

involves structural with physiological adaptations to

minimize salt concentrations of the cells or physiological Fig. 8 Photosynthetic rate (Pn) and stomatal conductance exclusion by root membranes. In addition to ion (Cs) at different photosynthetically active radiation (PAR) under NaCl treatment. Open and closed toxicity, salinity stress causes lower soil water symbols indicate the control and treated plants, potential, which can result in salinity-induced plant respectively. Data are the mean value with standard dehydration stress (Johnson, 1991). In case of deviation of three control plants and are the mean value of two treated plants (date of one plant was Mertoxylon palms, restricting the transpiration can be not available because of technical error). considered as one of the avoidance responses to salt Ehara et al.: Response of Metroxylon warburgii to Salt Stress 167

stress, that is, physiological adaptation with the physical treatment and presence of the pericarp and decrease in stomatal aperture, for maintaining a sarcotesta on seed germination in sago palm ( Rottb.). Seed Sci. & Technol. 29: 83-90. relatively lower Na+ concentration in the leaflets Ehara, H., H. Naito, C. Mizota and P. Ala 2003a. Distribution, especially at higher leaf positions through keeping growth environment and utilization of Metroyxlon palms in water status in the plant body. Absorbed Na+ into the Vanuatu. Sago Palm 10: 64-72. Ehara, H., H. Naito, C. Mizota and P. Ala 2003b. Agronomic roots was stored much more in the cortex, which features of Metroxylon palms growing on Gaua in the Banks contributed for the salt avoidance in this species. Islands, Vanuatu. Sago Palm 11:14-17. In conclusion, M. warburgii belongs to same Ehara, H., S. Susanto, C. Mizota, S. Hirose and T Matsuno 2000. Sago palm (Metroxylon sagu, ) production in the genus with sago palm has a mechanism to restrict the eastern archipelago of Indonesia: Variation in morphological influx of Na+ from the cortex into the stele of the roots characteristics and pith-dry matter yield. Econ. Bot. 54:197- and maintains a low Na+ concentration in the leaflets of 206. Flach, M. 1977. Yield potential of the sago palm and its upper active leaves by storing Na+ mainly in the petiole realization. In: Sago-'76: The Equatorial Swamp as a Natural at lower leaf positions. K+ distribution to the leaflets is Resource (Tan, K. ed.) The 1st International Sago not affected by the change in the Na+ concentration in Symposium (Kuala Lumpur) 157-177. Greenway, H. 1962a. Plant response to saline substrates. I. the roots and petioles in M warubrugii. The specific Growth and ion uptake of several varieties of Hordeum growth response of M warburgii to salt stress in vulgare during and after sodium chloride treatment. Aust. J. comparison with that of sago palm can be summarised Biolog. Sci. 15: 16-38. Greenway, H. 1962b. Plant response to saline substrates. II. as follows: 1) new leaf emergence is delayed, 2) leaf Chloride, sodium, and potassium uptake and translocation in senescence of lower position is accelerated, 3) the young plants of Hordeum vulgare during and after a short decrease in transpiration is large to, less than 50% of sodium chloride treatment. Aust. J. Biolog. Sci. 15: 39-57. Greenway, H., A. Gunn, M. Pitman, D. A. Thomas 1965. Plant control, 4) the increase in Na+ concentration is higher response to saline substrates. VI. Chloride, sodium, and in petiole rather than in roots. potassium uptake and distribution within the plant during ontogenesis of Hordeum vulgare. Aust. J. Biolog. Sci. 18: 525- Acknowledgments 540. Jeschke, W. D., C. A. Atkins and J. S. Pate 1985. 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塩 ス ト レ ス 下 に お け るMetroxylon warburgii Becc.の 部 位 別N+・K+濃 度

お よ び 関 連 生 理 特 性

江 原 宏1*・ 柴 田博 行1・ 内藤 整2・ 三 島 隆1・Philimon ALA3

1三 重大学大学院生物資源学研究科 2倉 敷芸術科学大学生命科学部 3Department ofForests, Vanuatu

要 約 サ ゴ ヤ シ(Metroxylon sagu Rottb.)と 同 じ属 の.M. warburgii(Heim)Becc.の,NaCl処 理 下 に お け る部 位 別 のNa+お よびK+濃 度,な ら び に 関 連 す る 生 理 的 特 性 に つ い て 検 討 した.11な い し13葉 期 の 実 生 を 用 い,日 本 の 夏 季 に 自然 光 の ガ ラ ス室 内 で36日 間 の342m M NaCl処 理(2%NaClに 相 当)を 行 っ た こ ろ,上 位 に 着 生 して い る 活 動 中 心 葉 に お い て は,小 葉 のNa+濃 度 は 高 ま らな か っ た.根 お よ び 下 位 の 葉 柄(含 葉 軸)にNa+が 蓄 積 され た こ と に よ っ て,小 葉,特 に 上 位 の 活 動 中 心 葉 へNa+の 移 行 が 妨 げ られ た こ と に よ る も の と 考 え られ た.ま た,根 を 中 心 部(中 心 柱 他)と 周 辺 部(皮 層 他)に 分 け て Na+濃 度 を 測 定 した と こ ろ,周 辺 部 に 比 べ て 中 心 部 で 低 か っ た こ と か ら,Na+が 中心 柱 に 流 入 して 地 上 部 へ 移 行 す る の を 妨 げ る よ う な機 構 が 存 在 す る も の と理 解 され た.一 方,小 葉 へ のK+の 分 配 は,処 理 に よ る 根 や 葉 柄 のNa+濃 度 の 上 昇 に 影 響 さ れ な か っ た.気 孔 コ ン ダ ク タ ン ス と単 位 葉 面 積 当 た り ク ロ ロ フ ィル 含 量 の低 下 に伴 い,光 合 成 速 度 も低 下 した. キ ー ワ ー ド:塩 害 回 避 性,気 孔 コ ン ダ ク タ ン ス,光 合 成 速 度,サ ゴ ヤ シ属 植 物,蒸 散 速 度,NaCl処 理

*Corresponding author

〒514-8507三 重 県 津 市 栗 真 町 屋 町 [email protected]