**2.2. Materials and methods**

of the culm of *S. kulinensis* has buds on nodes and continues to bifurcate. In contrast, there are no buds at lower part of the culm of *S. kulinensis*. The leaves of *S. kulinensis* can survive for relatively longer time, and its longevity ranges from 3 to 5 years. The culm height of *S. senanensis* is about 2 m, and its longevity is 5 years. The culm of *S. senanensis* has buds on every node. The leaf longevity of *S. senanensis* is about 2 years. In contrast, the culm height of *S. nipponica* is less than 1 m, and its longevity is also about 1 year. The buds of *S. nipponica* exist at the underground of the culm. The leaf longevity of *S. nipponica* is less than 1 year.

The three *Sasa* species have well-developed rhizome systems and are dominant at the forest floor in general forests of this region [14, 15]. As a result, the light environment under the *Sasa* species is quite dark, and regeneration of other species is suppressed [16]. Moreover, the *Sasa* species has high regeneration ability after disturbances. When forests suffer from forest fires, forest cannot restore; however, dwarf bamboo is able to regenerate as ground vegetation [17, 18]. The flowering period of the *Sasa* species is estimated to be 60–100 years [4]; however, information of flowering is still limited. Based on previous information, flowering of *Sasa* species occurs synchronously and often expands over 1000 ha in area [4, 19]. After flowering, numerous seeds are produced, and all culms of the *Sasa* species dies [4, 19], as does a mono-

**2. Ecophysiological characteristics of three** *Sasa* **species**

**Figure 2.** Morphological characteristics of the three *Sasa* species (modification from Makita [4]).

In the previous chapter, we summarized the ecological characteristics of the three dominant *Sasa* sp. in Northern Japan: *S. kurilensis*, *S. senanensis*, and *S. nipponica.* We showed specific

carpic plant.

188 Bamboo - Current and Future Prospects

**2.1. Background**

This research was conducted in an arboretum of the Hokkaido Research Center, Forestry and Forest products Research Institute (43°00′N, 141°23′E, 141 m a.s.l.) located in Sapporo City, Hokkaido, Japan. The annual mean, maximum, and minimum temperatures at the metrological station of this centre were 7.3, 35.7, and −22.8°C, respectively, from 1975 to 2003 [26]. The range of annual precipitation was from 581 to 1490 mm year−1 during 1975–2003 [26]. The maximum snow depth in winter was 130 cm [26]. In this arboretum, the subterranean stem of *S. kurilensis*, *S. senanensis*, and *S. nipponica* was planted in 1982. The size of planting area was 5 × 10 m for each *Sasa* species. Plantations of *Sasa* species were exposed to full sunlight the whole day because there were no surrounding trees around the plantation.

We measured the photosynthetic rate at light saturation (*Psat*, μmol m−2 s−1) from May to October 2004. The measurements were carried out at 10:00–15:00 each month. Second leaves counted from the top of culm of each *Sasa* species were used for the measurement of *Psat*. We selected four leaves of current and 2-year-old ones located at sunny positions. Measurements were made by using a portable gas analyzer (LI-6400, LI-COR Biosciences, Lincoln, NE, USA) under steady-state conditions (25°C, 36.0 Pa of CO<sup>2</sup> , and 1800 μmol m−2 s−1 photosynthetic photon flux using LED), which were previously determined [27].

After measuring photosynthetic rate, we sampled the leaves and analysed the chlorophyll concentration. The fresh mass of leaves were first measured, then crushed by liquid nitrogen, and finally extracted by dimethyl sulfoxide. Measurement of chlorophyll was done by a spectrophotometer (V560, JASCO Co., Tokyo, Japan), and its concentration was calculated by an equation [28]. The remaining leaf samples were dried at 80°C, for 4 days. After drying, we measured specific leaf area (SLA = leaf area per dry mass, cm<sup>2</sup> g−1, [29]). Leaf samples were ground to a fine powder using a sample mill (WB-1; Osaka Chemical Co., Osaka, Japan). The mass-based concentration of nitrogen (*N*mass, mmol g−1) was analysed using a NC analyser (NC-800, Sumika Chemical Analysis Service, Osaka). We also calculated the photosynthetic nitrogen use efficiency (PNUE, nmol mmol−1 s−1, [25]) as an indicator of photosynthetic apparatus allocation. PNUE was calculated by the following Eq. (1). We also calculated area-based concentration of nitrogen (*N*area, mmol m−2) from the value of SLA Eq. (2).

$$\text{PNUE} = P\_{\text{sat}} / N\_{\text{ava}} \times 1,000 \tag{1}$$

However, *P*sat of *S. nipponica* started to decrease from September. *P*sat of *S. senanensis* in June was significantly lower than *S. nipponica* (*P* < 0.001); however, *P*sat increased to 16 μmol m−2 s−1 from July to September. In contrast, flushing of leaves of *S. kurilensis* was in July, and *P*sat was significantly lower in July and August than other *Sasa* species (*P* < 0.001). In September, *P*sat of

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In 2-year-old leaves, all *Sasa* species showed high values of *P*sat in May when all species had not yet flushed new leaves. However, *P*sat of 2-year-old leaves was decreased from June. Especially, the culms of *S. nipponica* fell to the ground in June, and *P*sat was drastically decreased. *P*sat of *S. senanensis* and *S. kurilensis* was also decreased from July. However, *P*sat of *S. kurilensis* was maintained at 8 μmol m−2 s−1 until September, and these values were significantly higher in

The value of SLA was also different among the three *Sasa* species. For the current leaves, SLA in July and September showed significantly high values for *S. nipponica* than that for *S. senanensis* and *S. kurilensis* (**Figure 4**, *P* < 0.05). In contrast, SLA for current leaves of *S. kurilensis* was the lowest values from July to September. The values of SLA for current leaves decreased by time for all *Sasa* species. Compared to current and 2-year-old leaves, SLA showed low values for 2-year-old leaves for all *Sasa* species. From July, there was no significant difference in

Concentration of mass-based nitrogen (*N*mass) in current leaves showed the highest values in June for *S. nipponica* and *S. senanensis*; however, their values decreased by time (**Figure 5**). In the case of *S. kurilensis*, the decrease of *N*mass in current leaves was not clear. *N*mass for current leaves was significantly higher for *S. nipponica* from June to September than those for *S. senanensis* and *S. kurilensis* (*P* < 0.05). In October, *N*mass of *S. nipponica* showed similar value with *S. kurilensis*. As for the trend of 2-year-old leaves, all *Sasa* species decreased *N*mass with time. *N*mass in June of 2-year-old leaves of *S. nipponica* was significantly lower than the *N*mass of *S.* 

Compared with *N*mass, area-based nitrogen (*N*area) showed that its decrease by time was not obvious for current leaves. The peak of *N*area showed in June of 2-year-old leaves for *S. kurilensis*

**Figure 4.** Seasonal change of specific leaf area (SLA) for current and 2-year-old leaves of the three *Sasa* species (May to

October 2004, n = 4). Different letters indicate significant differences as calculated by Tukey test (*P* < 0.05).

*S. kurilensis* increased to 15 μmol m−2 s−1.

July, August, and September than that of *S. senanensis* (*P* < 0.05).

SLA of 2-year-old leaves among the three *Sasa* species.

*senanensis* and *S. kurilensis* (*P* < 0.05).

$$N\_{\text{area}} = 10,000 \,/\text{SLA} \times N\_{\text{mass}} \tag{2}$$

The value of *P*sat, SLA, concentrations of chlorophyll and nitrogen, and PNUE was examined using Tukey tests. The mean values were compared among *S. kurilensis*, *S. senanensis*, and *S. nipponica*.

#### **2.3. Results**

Concerning the value of *P*sat for the current leaves, *S. nipponica* showed high values (14 μmol m−2 s−1) from June when its leaves flushed (**Figure 3**). In July, *P*sat of *S. nipponica* increased to 18 μmol m−2 s−1, and its value was significantly higher than other *Sasa* species (*P* < 0.01).

**Figure 3.** Seasonal change of photosynthetic rate at light saturation (*P*sat) for current and 2-year-old leaves of the three *Sasa* species (May to October 2004, n = 4). Different letters indicate significant differences as calculated by Tukey test (*P* < 0.05).

However, *P*sat of *S. nipponica* started to decrease from September. *P*sat of *S. senanensis* in June was significantly lower than *S. nipponica* (*P* < 0.001); however, *P*sat increased to 16 μmol m−2 s−1 from July to September. In contrast, flushing of leaves of *S. kurilensis* was in July, and *P*sat was significantly lower in July and August than other *Sasa* species (*P* < 0.001). In September, *P*sat of *S. kurilensis* increased to 15 μmol m−2 s−1.

selected four leaves of current and 2-year-old ones located at sunny positions. Measurements were made by using a portable gas analyzer (LI-6400, LI-COR Biosciences, Lincoln, NE, USA)

After measuring photosynthetic rate, we sampled the leaves and analysed the chlorophyll concentration. The fresh mass of leaves were first measured, then crushed by liquid nitrogen, and finally extracted by dimethyl sulfoxide. Measurement of chlorophyll was done by a spectrophotometer (V560, JASCO Co., Tokyo, Japan), and its concentration was calculated by an equation [28]. The remaining leaf samples were dried at 80°C, for 4 days. After drying,

ground to a fine powder using a sample mill (WB-1; Osaka Chemical Co., Osaka, Japan). The mass-based concentration of nitrogen (*N*mass, mmol g−1) was analysed using a NC analyser (NC-800, Sumika Chemical Analysis Service, Osaka). We also calculated the photosynthetic nitrogen use efficiency (PNUE, nmol mmol−1 s−1, [25]) as an indicator of photosynthetic apparatus allocation. PNUE was calculated by the following Eq. (1). We also calculated area-based

 PNUE = *Psat* / *N*area × 1, 000 (1) *N*area = 10, 000 / SLA × *N*mass (2) The value of *P*sat, SLA, concentrations of chlorophyll and nitrogen, and PNUE was examined using Tukey tests. The mean values were compared among *S. kurilensis*, *S. senanensis*, and

Concerning the value of *P*sat for the current leaves, *S. nipponica* showed high values (14 μmol m−2 s−1) from June when its leaves flushed (**Figure 3**). In July, *P*sat of *S. nipponica* increased to 18 μmol m−2 s−1, and its value was significantly higher than other *Sasa* species (*P* < 0.01).

**Figure 3.** Seasonal change of photosynthetic rate at light saturation (*P*sat) for current and 2-year-old leaves of the three *Sasa* species (May to October 2004, n = 4). Different letters indicate significant differences as calculated by Tukey test

, and 1800 μmol m−2 s−1 photosynthetic

g−1, [29]). Leaf samples were

under steady-state conditions (25°C, 36.0 Pa of CO<sup>2</sup>

190 Bamboo - Current and Future Prospects

*S. nipponica*.

**2.3. Results**

(*P* < 0.05).

photon flux using LED), which were previously determined [27].

we measured specific leaf area (SLA = leaf area per dry mass, cm<sup>2</sup>

concentration of nitrogen (*N*area, mmol m−2) from the value of SLA Eq. (2).

In 2-year-old leaves, all *Sasa* species showed high values of *P*sat in May when all species had not yet flushed new leaves. However, *P*sat of 2-year-old leaves was decreased from June. Especially, the culms of *S. nipponica* fell to the ground in June, and *P*sat was drastically decreased. *P*sat of *S. senanensis* and *S. kurilensis* was also decreased from July. However, *P*sat of *S. kurilensis* was maintained at 8 μmol m−2 s−1 until September, and these values were significantly higher in July, August, and September than that of *S. senanensis* (*P* < 0.05).

The value of SLA was also different among the three *Sasa* species. For the current leaves, SLA in July and September showed significantly high values for *S. nipponica* than that for *S. senanensis* and *S. kurilensis* (**Figure 4**, *P* < 0.05). In contrast, SLA for current leaves of *S. kurilensis* was the lowest values from July to September. The values of SLA for current leaves decreased by time for all *Sasa* species. Compared to current and 2-year-old leaves, SLA showed low values for 2-year-old leaves for all *Sasa* species. From July, there was no significant difference in SLA of 2-year-old leaves among the three *Sasa* species.

Concentration of mass-based nitrogen (*N*mass) in current leaves showed the highest values in June for *S. nipponica* and *S. senanensis*; however, their values decreased by time (**Figure 5**). In the case of *S. kurilensis*, the decrease of *N*mass in current leaves was not clear. *N*mass for current leaves was significantly higher for *S. nipponica* from June to September than those for *S. senanensis* and *S. kurilensis* (*P* < 0.05). In October, *N*mass of *S. nipponica* showed similar value with *S. kurilensis*. As for the trend of 2-year-old leaves, all *Sasa* species decreased *N*mass with time. *N*mass in June of 2-year-old leaves of *S. nipponica* was significantly lower than the *N*mass of *S. senanensis* and *S. kurilensis* (*P* < 0.05).

Compared with *N*mass, area-based nitrogen (*N*area) showed that its decrease by time was not obvious for current leaves. The peak of *N*area showed in June of 2-year-old leaves for *S. kurilensis*

**Figure 4.** Seasonal change of specific leaf area (SLA) for current and 2-year-old leaves of the three *Sasa* species (May to October 2004, n = 4). Different letters indicate significant differences as calculated by Tukey test (*P* < 0.05).

Chlorophyll concentration for 2-year-old leaves of *S. kurilensis* and *S. senanensis* was maintained these values compared with current leaves, whereas its value of *S. nipponica* was decreased gradually. *S. kurilensis* had a significantly higher chlorophyll concentration in all months than that of S. *nipponica* and *S. senanensis* (*P* < 0.05). Concentration of chlorophyll for

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PNUE of current leaves showed significantly high values for *S. senanensis* from July compared with the other *Sasa* species (**Figure 7**, *P* < 0.05). In contrast, PNUE of current leaves of *S. nipponica* decreased from September. PNUE of current leaves of *S. kurilensis* increased from

For 2-year-old leaves, PNUE showed high in May; however, this value was decreased in June. From June to August, the value of PNUE was maintained these values for three *Sasa* species. In September, PNUE of *S. kurilensis* and *S. senanensis* was increased, whereas its value was decreased for *S. nipponica*. Compared with three *Sasa* species, PNUE for 2-year-old leaves of *S. kurilensis* was significantly higher from July to October than those for other *Sasa*

Based on the results, the ecophysiological characteristics of the three *Sasa* species were different. The leaf of *S. nipponica* showed high *P*sat from flushing (**Figure 3**). The leaf of *S. nipponica* also had high N (**Figure 5**), and this made it possible to maintain a high *P*sat concentration. Furthermore, the leaf of *S. nipponica* was thin with a high value of SLA (**Figure 4**). In general, thin leaves

the relatively thin leaf of *S. nipponica* has a big advantage to obtain a high photosynthetic rate

June, and its leaves were laid at a low layer of the plantation. *P*sat of 2-year-old leaves decreased (**Figure 3**), and the photosynthetic productivity of its leaf may have been small. However, we confirmed that the leaves of *S. nipponica* could survive over 1 year, even if the culm has fallen.

**Figure 7.** Seasonal change of photosynthetic nitrogen use efficiency (PNUE) for current and 2-year-old leaves of the three *Sasa* species (May to October 2004, n = 4). Different letters indicate significant differences as calculated by Tukey

diffusive conductance [25]; as a result, thin leaves show high *P*sat. So,

in its leaves. In contrast, 2-year-old culm of *S. nipponica* was fallen in

September. PNUE of current leaves was decreased for all *Sasa* species in October.

2-year-old leaves showed remarkable decrease from September.

species (*P* < 0.05).

**2.4. Discussion**

have a low value of CO<sup>2</sup>

through diffusion of CO<sup>2</sup>

test (*P* < 0.05).

**Figure 5.** Seasonal change of mass-based (*N*mass) and area-based (*N*area) concentrations of nitrogen for current and 2-yearold leaves of the three *Sasa* species (May to October 2004, n = 4). Different letters indicate significant differences as calculated by Tukey test (*P* < 0.05).

and *S. senanensis*, whereas its peak was in June of current leaves for *S. nipponica*. *N*area for current leaves of *S. nipponica* showed significantly higher than that of *S. senanensis* from June to August (*P* < 0.01). In contrast, *N*area for current leaves of *S. nipponica* did not show significant difference with *S. kurilensis* from July to September. In October, *N*area for current leaves showed significantly higher for *S. kurilensis* than those of other *Sasa* species (*P* < 0.001). Also, *N*area for 2-year-old leaves showed significantly higher for *S. kurilensis* than that for *S. nipponica* (*P* < 0.01). *N*area for 2-year-old of *S. senanensis* showed middle range between *S. kurilensis* and *S. nipponica*, and its trend was similar with *S. kurilensis*.

Total chlorophyll (Chl a+b) concentration showed the low value after flushing and increased in August for *S. kurilensis* and *S. nipponica* and in June for *S. senanensis* (**Figure 6**). Compared with *Sasa* species, chlorophyll concentration was significantly high value for current leaves of *S. kurilensis* in September and October (**Figure 6**, *P* < 0.05). In August, chlorophyll concentration of current leaves was significantly higher at *S. nipponica* compared to *S. kurilensis* and *S. senanensis* (*P* < 0.05).

**Figure 6.** Seasonal change of chlorophyll (a + b) concentration for current and 2-year-old leaves of the three *Sasa* species (May to October 2004, n = 4). Different letters indicate significant differences as calculated by Tukey test (*P* < 0.05).

Chlorophyll concentration for 2-year-old leaves of *S. kurilensis* and *S. senanensis* was maintained these values compared with current leaves, whereas its value of *S. nipponica* was decreased gradually. *S. kurilensis* had a significantly higher chlorophyll concentration in all months than that of S. *nipponica* and *S. senanensis* (*P* < 0.05). Concentration of chlorophyll for 2-year-old leaves showed remarkable decrease from September.

PNUE of current leaves showed significantly high values for *S. senanensis* from July compared with the other *Sasa* species (**Figure 7**, *P* < 0.05). In contrast, PNUE of current leaves of *S. nipponica* decreased from September. PNUE of current leaves of *S. kurilensis* increased from September. PNUE of current leaves was decreased for all *Sasa* species in October.

For 2-year-old leaves, PNUE showed high in May; however, this value was decreased in June. From June to August, the value of PNUE was maintained these values for three *Sasa* species. In September, PNUE of *S. kurilensis* and *S. senanensis* was increased, whereas its value was decreased for *S. nipponica*. Compared with three *Sasa* species, PNUE for 2-year-old leaves of *S. kurilensis* was significantly higher from July to October than those for other *Sasa* species (*P* < 0.05).

#### **2.4. Discussion**

and *S. senanensis*, whereas its peak was in June of current leaves for *S. nipponica*. *N*area for current leaves of *S. nipponica* showed significantly higher than that of *S. senanensis* from June to August (*P* < 0.01). In contrast, *N*area for current leaves of *S. nipponica* did not show significant difference with *S. kurilensis* from July to September. In October, *N*area for current leaves showed significantly higher for *S. kurilensis* than those of other *Sasa* species (*P* < 0.001). Also, *N*area for 2-year-old leaves showed significantly higher for *S. kurilensis* than that for *S. nipponica* (*P* < 0.01). *N*area for 2-year-old of *S. senanensis* showed middle range between *S. kurilensis* and *S. nip-*

**Figure 5.** Seasonal change of mass-based (*N*mass) and area-based (*N*area) concentrations of nitrogen for current and 2-yearold leaves of the three *Sasa* species (May to October 2004, n = 4). Different letters indicate significant differences as

Total chlorophyll (Chl a+b) concentration showed the low value after flushing and increased in August for *S. kurilensis* and *S. nipponica* and in June for *S. senanensis* (**Figure 6**). Compared with *Sasa* species, chlorophyll concentration was significantly high value for current leaves of *S. kurilensis* in September and October (**Figure 6**, *P* < 0.05). In August, chlorophyll concentration of current leaves was significantly higher at *S. nipponica* compared to *S. kurilensis* and *S. senanensis* (*P* < 0.05).

**Figure 6.** Seasonal change of chlorophyll (a + b) concentration for current and 2-year-old leaves of the three *Sasa* species (May to October 2004, n = 4). Different letters indicate significant differences as calculated by Tukey test (*P* < 0.05).

*ponica*, and its trend was similar with *S. kurilensis*.

calculated by Tukey test (*P* < 0.05).

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Based on the results, the ecophysiological characteristics of the three *Sasa* species were different. The leaf of *S. nipponica* showed high *P*sat from flushing (**Figure 3**). The leaf of *S. nipponica* also had high N (**Figure 5**), and this made it possible to maintain a high *P*sat concentration. Furthermore, the leaf of *S. nipponica* was thin with a high value of SLA (**Figure 4**). In general, thin leaves have a low value of CO<sup>2</sup> diffusive conductance [25]; as a result, thin leaves show high *P*sat. So, the relatively thin leaf of *S. nipponica* has a big advantage to obtain a high photosynthetic rate through diffusion of CO<sup>2</sup> in its leaves. In contrast, 2-year-old culm of *S. nipponica* was fallen in June, and its leaves were laid at a low layer of the plantation. *P*sat of 2-year-old leaves decreased (**Figure 3**), and the photosynthetic productivity of its leaf may have been small. However, we confirmed that the leaves of *S. nipponica* could survive over 1 year, even if the culm has fallen.

**Figure 7.** Seasonal change of photosynthetic nitrogen use efficiency (PNUE) for current and 2-year-old leaves of the three *Sasa* species (May to October 2004, n = 4). Different letters indicate significant differences as calculated by Tukey test (*P* < 0.05).

These characteristics that show high photosynthetic capacity and high concentration of nitrogen for younger leaf and short leaf longevity are corresponded with fast-growing species [25]. In general, fast-growing species shows that photosynthetic rate is decreased drastically by increase of leaf age [21, 30]. This trend is clear for evergreen oak compared with conifer species [30]. Moreover, there are a fast-growing species among same genus of *Picea*, and *Picea abies* and *Picea glauca* are considered as fast-growing species [21]. These species showed high photosynthetic rate for younger leaves; however, their high values were not maintained. Also, fast-growing species have a high rate of leaf turnover [31]. Woody species have a leaf turnover mechanism, and when old leaves are lost, leaf nitrogen is retranslocated to younger leaves [32]. *S. nipponica* showed continuous decrease of *N*mass (**Figure 6**), and its trait is probably related with retranslocation of nitrogen. *S. nipponica* may be retranslocated nitrogen from old to young leaves, thus maintaining high photosynthetic capacity.

(LHCP) at thylakoids in the chloroplast [35]. As an increase of chlorophyll contributes to an increase in photon absorption, chlorophyll concentration shows a positive relationship with photosynthetic rate within the same species [35]. In the case of 2-year-old leaves of *S. kurilensis*, *P*sat showed a high value despite not having a high nitrogen concentration (**Figures 3** and **5**) and small SLA (**Figure 4**). There is a possibility that 2-year-old leaves of *S. kurilensis* allocate nitrogen to chlorophyll (Chl/N) and reinforce the absorption and transferring capacity of photon. Consequently, *S. kurilensis* may use absorbed photo efficiently for increasing photo-

Therefore, aged leaves of *S. kurilensis* are considered to be shaded by new leaves that flushed later on; therefore, mutual shading occurs. High concentration of chlorophyll in 2-year-old

*Sasa* species regenerates at the same place with clonal development, and these traits cannot be simply classified into fast- and slow-growing species as other species. We regard the *Sasa* species as follows: *S. nipponica* is classified as a fast-growing species, whereas *S. kulinensis* are slow-growing species. Indeed, ecophysiological characteristics of *Sasa* sp. are the same as slowand fast-growing species as found in other plant species. *S. senanensis* cannot be classified as two growing types and showed intermediate characteristics between fast- and slow-growing

Related to the habitat of the three *Sasa* species, edaphic habitat of *S. nipponica* is considered to be the deep humus layer and A-horizon [36]. The characteristics of a fast-growing species is to have an advantage in a fertile habitat, and the growth trait of *S. nipponica* shows a rapid turnover of leaves and culms [4], which is considered to be suitable for the habitat. We conclude that ecophysiological characteristics of *S. nipponica* are adapted to fertile habitats. The distribution area of *S. nipponica* is classified as low altitudes, facing to the coast of Pacific Ocean where the summers are relatively cloudy with high humidity and the high photosynthetic performance of *S. nipponica* is kept [8]. Moreover, although the snowy period there is short, the soil freezes with cold climate [5]. *Sasa* cannot keep evergreen leaves during winter; hence, the *Sasa* species must produce new leaves from spring after the death of leaves of previous

In contrast, the distribution of *S. kurilensis* is hillsides and slope of valley sides where soil depth is shallow [36]. In general, these locations restrict plant growth. The leaves and culms of *S. kurilensis* can survive for several years [4], and these traits may exist to compensate for low photosynthetic productivity. *S. kurilensis* showed high concentration of chlorophyll and PNUE for 2-year-old leaves (**Figures 6** and **7**). This characteristic is suitable for conditions where resources are limited*.* Thus, we conclude that ecophysiological characteristics of *S. kurilensis* reflect the adaptability to infertile habitats. *S. kurilensis* distributes at high mountain areas in Hokkaido Island (**Figure 1**). The area of *S. kurilensis*

year. Its high photosynthetic rate may be compensating short leaf longevity.

probably corresponds with deep snow and harsh environmental conditions.

leaves of *S. kulinensis* may have had the advantage under shady conditions.

diffusion in its leaf. Leaf longevity of *S. kurilensis* is 3–5 years [4].

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system by decreasing CO<sup>2</sup>

**3. Conclusion**

species.

For the other *Sasa* species, the maximum value of *P*sat for current leaves of *S. kurilensis* was lower than other species; however, its value for 2-year-old leaves was maintained for 5 months (**Figure 3**). These traits are corresponded with slow-growing species [25]. The concrete slow-growing species are *Taxus baccata*, *Picea mariana*, and *Picea rubens* [21, 30]. The leaf longevities of these species were over 5 years, and photosynthetic rates showed high value for 6-year-old leaves [21, 30]. Also, maximum leaf longevity of *S. kurilensis* is 5 years [4], and its ecophysiological characteristics are similar with other slow-growing species. Also, slowgrowing species have a characteristic to maintain high value of PNUE for aged leaves [21, 30], and *S. kurilensis* showed high PNUE for 2-year-old leaves (**Figure 7**). This trait is related with the maintenance of photosynthetic rate for long period.

On other traits, slow-growing species has thick leaves [21, 25]. Leaves of *S. kurilensis* showed a low value of SLA (**Figure 4**), which was characterised by thick leaves. In general, species with a small SLA allocates nitrogen to the leaf cell wall and increases toughness of the cell [33]. This trait contributes to the extent of leaf longevity [34]. Thus, allocation of nitrogen in leaves for *S. kurilensis* is probably larger for cell wall than for protein of photosynthetic apparatus. As a result, *S. kurilensis* may make leaves with a long longevity but with a low photosynthetic rate.

*P*sat of *S. senanensis* for current leaves showed high values in August and September (**Figure 3**). In contrast, current leaves of *S. senanensis* were thick (**Figure 4**), and *N*area and *N*mass were low compared with *S. nipponica* (**Figure 5**). Thus, ecophysiological characteristics of *S. senanensis* are not similar with *S. nipponica*. In contrast, leaves of *S. senanensis* were thin (**Figure 4**) and short longevity (about 2 years, [4]) compared with *S. kurilensis*. Thus, ecophysiological characteristics of *S. senanensis* are also not similar with *S. kurilensis*. Consequently, ecophysiological characteristics of *S. senanensis* are intermediate between fast- and slow-growing species. On the remarkable characteristics of *S. senanensis*, PNUE showed the highest value for current leaves (**Figure 7**). *S. senanensis* may allocate more nitrogen to protein of photosynthesis apparatus compared with other *Sasa* species. Similar ecophysiological characteristics were reported for *Pinus pinea* and *Picea jezoensis* var. *hondoensis* [21, 30].

In addition, the trait of chlorophyll concentration also concerns with ecophysiological characteristics. The concentration of chlorophyll showed high values for *S. kurilensis*, especially 2-year-old leaves (**Figure 6**). In general, chlorophylls have light harvesting complex proteins (LHCP) at thylakoids in the chloroplast [35]. As an increase of chlorophyll contributes to an increase in photon absorption, chlorophyll concentration shows a positive relationship with photosynthetic rate within the same species [35]. In the case of 2-year-old leaves of *S. kurilensis*, *P*sat showed a high value despite not having a high nitrogen concentration (**Figures 3** and **5**) and small SLA (**Figure 4**). There is a possibility that 2-year-old leaves of *S. kurilensis* allocate nitrogen to chlorophyll (Chl/N) and reinforce the absorption and transferring capacity of photon. Consequently, *S. kurilensis* may use absorbed photo efficiently for increasing photosystem by decreasing CO<sup>2</sup> diffusion in its leaf. Leaf longevity of *S. kurilensis* is 3–5 years [4]. Therefore, aged leaves of *S. kurilensis* are considered to be shaded by new leaves that flushed later on; therefore, mutual shading occurs. High concentration of chlorophyll in 2-year-old leaves of *S. kulinensis* may have had the advantage under shady conditions.
