2. Results2.1. Effects of NaCl on t

2. Results
2.1. Effects of NaCl on tomato growth
In LN medium (0.1 mM NO3–), tomato biomass was about 50% relative to that in HN medium (5 mM NO3–) (Fig. 1A).
Exposure of plants to 100 mM NaCl during 10 days reduced the leaf surface by 35% and 10% in HN and LN plants, respectively (Fig. 1A). DW production was decreased by 35% in HN plants and by 20% in LN plants (Fig. 1A). In both plants, leaves and stems-petioles were more affected by salt stress than roots. In HN plants, salinity decreased DW production in the leaves (40%), stems-petioles (30%) and roots (20%). In LN plants, DW production was decreased by 25% in the leaves and stems-petioles and by 10% in roots. Total extractable chlorophyll (Chl) decreased in HN leaves
with higher salt sensitivity of Chl a (Fig. 1B). In LN leaves, total leaf Chl contents were not affected by salt treatment. The changes in carotenoids (cart) contents by NaCl were low in both HN and LN plants (Fig. 1B). The NaCl treatment
decreased soluble protein contents by about 20% and 15% in the leaves from HN and LN plants, respectively (Fig. 1C). In
HN plants, soluble protein contents slightly increased in the stems-petioles and roots. In contrast, the increase in soluble
protein contents were observed in stems-petioles of salt treated LN plants (Fig. 1C).
2.2. Effects of NaCl on the enzymes of nitrogen metabolism during a day/night cycle
2.2.1. NR and activation state
The dark to light transition induced a fast increase in nitratereductase activity (NRA) in the leaves (Fig. 2A, B). Leaf NRA
in HN plants was higher than that in LN plants. Maximum NRA (NRAmax) occurred 3–6 hours after illumination. NRAmax
was about 2.7-fold higher in HN than in LN leaves. By the addition of NaCl, the NRAmax was inhibited in HN and
LN plants (Fig. 2A, B). The presence of NaCl did not affect the timing of the NRAmax, although it reduced the amplitude of
the changes in both HN and LN plants. The leaf NR activation state showed a similar pattern to that of activity (Fig. 2A, B).
The highest NR activation state (80%) occurred concomitantly with the NRAmax in both HN and LN plants. Under NaCl
stress, the NR activation state and NRA did not show similar diurnal changes. In both HN and LN plants, the NR activation
state was diminished in the light, but it was increased in darkness. The NRA exhibited a clear diurnal pattern in the stemspetioles (Fig. 2A, B). NRA was higher in HN than that in LN plants, and it increased in the night and reached maximum activity after 3 hours of illumination in both HN and LN plants. It can be noted that stem-petiole NRA decreased in the light despite a high NR activation state (Fig. 2A, B). This may reflect the NR protein synthesis rather than a NR inactivation via a phosphorylation/dephosphorylation process. In darkness, the NRA and NR activation state remained at lower levels. Salt stress inhibited NRA, but NRA showed a similar diurnal changes in both HN and LN plants. However, the NR activation state was not changed by salt stress in LN plants (Fig. 2B). In the roots, NRA was higher in HN than in the LN plants, and it showed a similar diurnal pattern to that found in the stemspetioles. NRA showed a peak 3 hours after illumination in both HN and LN plants (Fig. 2A, B). The NRA and NR activation state exhibited similar diurnal changes. In contrast to the leaves and stems-petioles, the NaCl stress stimulated NRA in both HN and LN plant roots. However, the diurnal pattern remained similar with a peak 3 hours into the light phase. The increase in the root NRA by the salt stress was associated with an increase in the NR activation state (Fig. 2A, B).
2.2.2. NiR
There were no diurnal changes in the specific nitrite reductase
activity (NiRA), irrespective of the plant tissue, the nitrogen regime and NaCl treatment (data not shown). The high
nitrogen regime increased NiRA in the leaves, stems-petioles and roots relative to the low nitrogen regime (Table 1). The addition of 100 mM NaCl decreased the leaf NiRA by about 15% in HN plants and by 30% in LN plants (Table 1). NiRA
levels were about ninefold and fivefold higher than the NRA in HN and LN plant leaves, respectively (Fig. 2A, B and Table 1).In both N medium, salt stress provoked a slight decrease (10–12%) of NiRA in the stems-petioles and roots. NiRA was
10–20-fold higher than NRA in the stems-petioles, and at least 10-fold higher than NRA in roots (Fig. 2A, B and Table 1).
2.2.3. GS
In the leaves of HN plants, the total GS activity showed a diurnal change (Fig. 3A). GS activity remained high in the dark
period, and it started to decline before the beginning of the light period to a minimum level at the middle of the light period. GS protein was detected only as a GS2 isoform in the leaves (Fig. 4A). During the light phase, the highest GS protein amount was associated with the high GS activity at 21 h (Fig. 3A). The addition of NaCl inhibited the total GS activity, and a similar diurnal change was observed showing a minimum level at the middle of the light period. GS activity did not strictly correlate with the GS protein. At 6–12 hours after illumination, GS activity was inhibited by 40–60% (Fig. 3A), whereas GS protein content was lowered only by 17% (Fig. 4A). GS activity in LN plant leaves showed lesser
changes during the day/night cycle (Fig. 3B), and was less affected by salinity than in HN plant leaves. GS activity levels
were similar to those obtained in the leaves from HN control plants. Salt stress decreased GS protein and activity by about
35% in LN plant leaves during the early hours of light period (Fig. 4B). GS exhibited contrasting diurnal changes in the stemspetioles from both HN and LN plants (Fig. 3A, B). The GS activity peak occurred 6 h after illumination, then it declined gradually until the end of the light period. The GS activity was slightly decreased by NaCl in the HN plants (Fig. 3A). The salt stress induced a pronounced decrease of GS activity in the LN plants in the second half of the light period (Fig. 3B). Similar diurnal variations of GS activity were observed in the roots from HN plants (Fig. 3A). The activity was higher during the second part of the light period, and it decreased progressively during darkness. However, in the LN plants, GS was lower in the light period and displayed an early activity peak in the dark, 3 h before illumination (Fig. 3B). The addition of NaCl increased GS activity in the root with a similar diurnal pattern in HN and LN plants (Fig. 3A, B).
2.2.4. Glutamate synthase
Fd-GOGAT represented the major form of the enzyme in the leaves, and NADH-GOGAT activity accounted for less than 30% of the Fd-GOGAT activity (data not shown). Fd- GOGAT activity exhibited diurnal changes (Fig. 3A). It was progressively increased after illumination and reached a maximum of activity at the second half of light period (15–18 h).
The highest Fd-GOGAT activity levels were concurrent with high Fd-GOGAT protein contents (Fig. 4C). Low activity
levels were measured at night, despite a high Fd-GOGAT protein amounts. The inhibition of Fd-GOGAT activity by NaCl occurred during the first hours following illumination. Fd-GOGAT activity was decreased by 40–60%. It was associated
with about 30–50% decrease in Fd-GOGAT protein.
2.2.5. Glutamate dehydrogenase (GDH)
There were no clear diurnal changes in GDH activity in the HN plant tissues. In HN untreated plants, NAD-GDH deaminating activity in the leaves was sixfold higher than NADHGDH aminating activity (Table 2). In contrast, aminating activity was always higher than deaminating activity in LN plants leaves (Fig. 5). The addition of 100 mM NaCl to HN medium inhibited deaminating activity by about 70% and induced aminating activity (sixfold) (Table 2). In LN plants, NaCl treatment induced both aminating and deaminating activities in the leaves, giving an apparent aminating activity peak in the second half of light cycle (Fig. 5). Under salt stress, LN plants preserved NADH-GDH/NAD-GDH ratios in the leaves, similar to those in control plants (Table 3). Whereas this ratio was enhanced in HN plant leaves; it was increased by NaCl treatment ranging from 0.2 to 6. The aminating activity was higher than the deaminating activity in the stems-petioles and roots, irrespective of nitrogen regime (Fig. 5 and Table 2). The NaCl stress inhibited the deaminating activity in the stems-petioles (50–60%) and roots (30%) from both HN and LN plants, except that the deaminating activity in the LN roots was stimulated. The aminating activity was stimulated by NaCl in the stems-petioles and roots from LN and HN plants (Fig. 5 and Table 2). We calculated nearly threefold and twofold increase in the aminating/ deaminating ratio in the stems-petioles from HN and LN treated plants, respectively (Table 3). It can be noted that high aminating activity was detected in the roots from control as well as treated LN plants. The NADH-GDH/NAD-GDH ratio
in the LN plant roots remained high despite the salt stress (Table 3).

ผลลัพธ์ (ไทย) 1:

2. ผลลัพธ์2.1. ผลของ NaCl มะเขือเทศเจริญเติบโตใน LN (0.1 mM NO3-), มะเขือเทศชีวมวลถูกประมาณ 50% เมื่อเทียบกับที่ใน HN (5 mM NO3-) (Fig. 1A)แสงของพืช 100 มม. NaCl ในระหว่างวันที่ 10 ลดลงผิวใบ โดย 35% และ 10% ในพืช HN และ LN ตามลำดับ (Fig. 1A) ผลิต DW ถูกลดลง 35% ในพืช HN และ 20% ในพืช LN (Fig. 1A) ในทั้งสองพืช ใบและลำต้น-petioles ขึ้นถูกกระทบจากความเครียดเกลือมากกว่าราก ในพืช HN เค็มลดลงผลิต DW ในใบไม้ (40%), ลำต้น-petioles (30%) และราก (20%) ใน LN พืช ผลิต DW ถูกลดลง 25% ในใบและลำต้น petioles และ 10% ในราก รวม extractable คลอโรฟิลล์ (Chl) ลดลงในใบไม้ HNมีความไวเกลือสูงของ Chl (Fig. 1B) ในใบไม้ LN รวม Chl เนื้อหาไม่ถูกกระทบจากเกลือ การเปลี่ยนแปลงในเนื้อหา carotenoids (รถเข็น) โดย NaCl ได้ต่ำสุดในพืชทั้ง HN และ LN (Fig. 1B) รักษา NaClลดเนื้อหาโปรตีนที่ละลายน้ำประมาณ 20% และ 15% ในใบจากพืช HN และ LN ตามลำดับ (Fig. 1C) ในพืช HN เนื้อหาโปรตีนที่ละลายน้ำเพิ่มขึ้นเล็กน้อยใน petioles ลำต้นและราก ในทางตรงข้าม เพิ่มการละลายโปรตีนเนื้อหาถูกสังเกตในลำ petioles เกลือบำบัดพืช LN (Fig. 1C)2.2. ผลของ NaCl เอนไซม์ของไนโตรเจนในระหว่างรอบกลางวัน/กลางคืน2.2.1. NR และเปิดใช้งานสถานะมืดในการเปลี่ยนแสงทำให้เกิดการเพิ่มขึ้นอย่างรวดเร็วในกิจกรรม nitratereductase (NRA) ในใบไม้ (Fig. 2A, B) ใบไม้ NRAในพืช HN ได้สูงกว่าพืช LN สูงสุด NRA (NRAmax) เกิด 3-6 ชั่วโมงหลังจากไฟส่องสว่าง NRAmaxมีประมาณ 2.7-fold สูงใน HN กว่าในใบ LN ด้านนอกของ NaCl, NRAmax ถูกห้ามใน HN และLN พืช (Fig. 2A, B) ของ NaCl ไม่มีผลต่อเวลาของ NRAmax แม้ว่ามันลดความกว้างของการเปลี่ยนแปลงในพืชทั้ง HN และ LN รัฐเปิด NR ใบแสดงให้เห็นรูปแบบคล้ายกับกิจกรรม (Fig. 2A, B)สูงสุด NR เปิดใช้งานสถานะ (80%) เกิดขึ้น concomitantly กับ NRAmax ในพืชทั้ง HN และ LN ภายใต้ NaClความเครียด สถานะการเปิดใช้งาน NR และ NRA ได้แสดง diurnal เปลี่ยนคล้าย ในพืชทั้ง HN และ LN เปิด NRstate was diminished in the light, but it was increased in darkness. The NRA exhibited a clear diurnal pattern in the stemspetioles (Fig. 2A, B). NRA was higher in HN than that in LN plants, and it increased in the night and reached maximum activity after 3 hours of illumination in both HN and LN plants. It can be noted that stem-petiole NRA decreased in the light despite a high NR activation state (Fig. 2A, B). This may reflect the NR protein synthesis rather than a NR inactivation via a phosphorylation/dephosphorylation process. In darkness, the NRA and NR activation state remained at lower levels. Salt stress inhibited NRA, but NRA showed a similar diurnal changes in both HN and LN plants. However, the NR activation state was not changed by salt stress in LN plants (Fig. 2B). In the roots, NRA was higher in HN than in the LN plants, and it showed a similar diurnal pattern to that found in the stemspetioles. NRA showed a peak 3 hours after illumination in both HN and LN plants (Fig. 2A, B). The NRA and NR activation state exhibited similar diurnal changes. In contrast to the leaves and stems-petioles, the NaCl stress stimulated NRA in both HN and LN plant roots. However, the diurnal pattern remained similar with a peak 3 hours into the light phase. The increase in the root NRA by the salt stress was associated with an increase in the NR activation state (Fig. 2A, B).2.2.2. NiRThere were no diurnal changes in the specific nitrite reductaseactivity (NiRA), irrespective of the plant tissue, the nitrogen regime and NaCl treatment (data not shown). The highnitrogen regime increased NiRA in the leaves, stems-petioles and roots relative to the low nitrogen regime (Table 1). The addition of 100 mM NaCl decreased the leaf NiRA by about 15% in HN plants and by 30% in LN plants (Table 1). NiRAlevels were about ninefold and fivefold higher than the NRA in HN and LN plant leaves, respectively (Fig. 2A, B and Table 1).In both N medium, salt stress provoked a slight decrease (10–12%) of NiRA in the stems-petioles and roots. NiRA was10–20-fold higher than NRA in the stems-petioles, and at least 10-fold higher than NRA in roots (Fig. 2A, B and Table 1).2.2.3. GSIn the leaves of HN plants, the total GS activity showed a diurnal change (Fig. 3A). GS activity remained high in the darkperiod, and it started to decline before the beginning of the light period to a minimum level at the middle of the light period. GS protein was detected only as a GS2 isoform in the leaves (Fig. 4A). During the light phase, the highest GS protein amount was associated with the high GS activity at 21 h (Fig. 3A). The addition of NaCl inhibited the total GS activity, and a similar diurnal change was observed showing a minimum level at the middle of the light period. GS activity did not strictly correlate with the GS protein. At 6–12 hours after illumination, GS activity was inhibited by 40–60% (Fig. 3A), whereas GS protein content was lowered only by 17% (Fig. 4A). GS activity in LN plant leaves showed lesserchanges during the day/night cycle (Fig. 3B), and was less affected by salinity than in HN plant leaves. GS activity levelswere similar to those obtained in the leaves from HN control plants. Salt stress decreased GS protein and activity by about35% in LN plant leaves during the early hours of light period (Fig. 4B). GS exhibited contrasting diurnal changes in the stemspetioles from both HN and LN plants (Fig. 3A, B). The GS activity peak occurred 6 h after illumination, then it declined gradually until the end of the light period. The GS activity was slightly decreased by NaCl in the HN plants (Fig. 3A). The salt stress induced a pronounced decrease of GS activity in the LN plants in the second half of the light period (Fig. 3B). Similar diurnal variations of GS activity were observed in the roots from HN plants (Fig. 3A). The activity was higher during the second part of the light period, and it decreased progressively during darkness. However, in the LN plants, GS was lower in the light period and displayed an early activity peak in the dark, 3 h before illumination (Fig. 3B). The addition of NaCl increased GS activity in the root with a similar diurnal pattern in HN and LN plants (Fig. 3A, B).2.2.4. Glutamate synthaseFd-GOGAT represented the major form of the enzyme in the leaves, and NADH-GOGAT activity accounted for less than 30% of the Fd-GOGAT activity (data not shown). Fd- GOGAT activity exhibited diurnal changes (Fig. 3A). It was progressively increased after illumination and reached a maximum of activity at the second half of light period (15–18 h).The highest Fd-GOGAT activity levels were concurrent with high Fd-GOGAT protein contents (Fig. 4C). Low activitylevels were measured at night, despite a high Fd-GOGAT protein amounts. The inhibition of Fd-GOGAT activity by NaCl occurred during the first hours following illumination. Fd-GOGAT activity was decreased by 40–60%. It was associatedwith about 30–50% decrease in Fd-GOGAT protein.2.2.5. Glutamate dehydrogenase (GDH)There were no clear diurnal changes in GDH activity in the HN plant tissues. In HN untreated plants, NAD-GDH deaminating activity in the leaves was sixfold higher than NADHGDH aminating activity (Table 2). In contrast, aminating activity was always higher than deaminating activity in LN plants leaves (Fig. 5). The addition of 100 mM NaCl to HN medium inhibited deaminating activity by about 70% and induced aminating activity (sixfold) (Table 2). In LN plants, NaCl treatment induced both aminating and deaminating activities in the leaves, giving an apparent aminating activity peak in the second half of light cycle (Fig. 5). Under salt stress, LN plants preserved NADH-GDH/NAD-GDH ratios in the leaves, similar to those in control plants (Table 3). Whereas this ratio was enhanced in HN plant leaves; it was increased by NaCl treatment ranging from 0.2 to 6. The aminating activity was higher than the deaminating activity in the stems-petioles and roots, irrespective of nitrogen regime (Fig. 5 and Table 2). The NaCl stress inhibited the deaminating activity in the stems-petioles (50–60%) and roots (30%) from both HN and LN plants, except that the deaminating activity in the LN roots was stimulated. The aminating activity was stimulated by NaCl in the stems-petioles and roots from LN and HN plants (Fig. 5 and Table 2). We calculated nearly threefold and twofold increase in the aminating/ deaminating ratio in the stems-petioles from HN and LN treated plants, respectively (Table 3). It can be noted that high aminating activity was detected in the roots from control as well as treated LN plants. The NADH-GDH/NAD-GDH ratioin the LN plant roots remained high despite the salt stress (Table 3).