Hideyasu Fujiyama

Difference in -response of rice and tomato subjected to sodium salinization to the addition of calcium

Abstract Rice (Oryza sativa L. cv. Yamabiko) and tomato (Lycopersicon esculentum Mill cv. Saturn) plants were subjected to Na-salinization (80 mmol( + ) kg-1) in hydroponics. The effect of the addition of Ca on their growth was analyzed in terms of transpiration, ion uptake, and ion transporto. The addition of 10 mmol( + ) kg-1 Ca improved rice growth by decreasing the Na uptake and increasing the K and Ca uptake. It was worth noting that the Na uptake accompanied with water uptake (transpiration) was not affected by the addition of Ca. A close relationship was found in rice among the osmotic potential, cumulative transpiration, and top dry weight; The growth of rice, therefore, seemed to depend on the osmotic potential of the solution. The growth suppression of the tops and roots brought about by Na and recovery by the addition of Ca were greater for tomato. Ca improved tomato growth by reducing the Na uptake and increasing the uptake of K and Ca, as was observed in rice. The selectivity of plants for po...

Characteristics of Nitrate Uptake by Plants Under Salinity

ABSTRACT Under salt stress conditions, the uptake of nitrogen (N) by plants is generally suppressed. The objective of this study was to clarify the mechanism of inhibition of NO3 absorption under highly saline media prepared from NaCl or Na2SO4. Tomato (Lycopersicon esculentum Mill cv. Saturn) and rice (Oryza sativa L. cv. Koshihikari) were subjected to three N levels of 0.7 mmol L−1 (LN), 7 mmol L−1 (MN), and 14 mmol L−1 (HN) under the same concentration (100 mM) of NaCl or Na2SO4 salinity. The N level of non-saline control was 7 mM. For both species the shoot dry weights (DW) of salt-treated plants were significantly lower than those grown in non-saline (CO) conditions. The application of N significantly enhanced shoot DW of tomato under SO4 salinity, while it had no effect on tomato growth under chloride (Cl) salinity. In rice, the LN level resulted in better growth than MN and HN levels. Nitrate-N concentration in both species was significantly increased by increasing N level in the solution. A large difference in NO3-N concentration between Cl and SO4 salinity was observed under MN and HN levels in tomato, and under LN and MN levels in rice, indicating an antagonism between Cl and NO3-N ions. Also, a close relationship between cumulative transpiration and NO3-N concentration in the shoots was observed for tomato. This indicates that NO3 absorption is related to water uptake in tomato. In contrast, not much difference was observed in cumulative transpiration among N levels in rice, which may indicate that transpiration was not related to NO3 uptake. However, the antagonism is considered not to be as strong as the relation between NO3 absorption and transpiration in tomato. It appeared that the inhibition of NO3-N absorption in tomato was more strongly related to reduced water uptake than to Cl antagonism from salt stress.

Ameliorative effect of potassium on rice and tomato subjected to sodium salinization

Abstract Rice (Oryza sativa L. cv. Yamabiko) and tomato (Lycopersicon esculentum Mill cv. Saturn) plants subjected to Na-salinization (NA: 80 mmol( + ) kg-1 Na) in hydroponics were grown after the addition of K at five concentrations (K1: 10, K2: 20, K3: 30, K4: 40, K5: 50 mmol( + ) kg-1). The effect of K on their growth was analyzed in terms of transpiration, cation uptake, and transport. A similar tendency for the above parameters was obtained in both species. The addition of 10 mmol( + ) kg-1 K improved the growth by decreasing the content of Na and increasing the K content of the plants. The growth of the plants, however, was reduced along with the increase of the K concentration and became comparable to that of NA at K5. The total cation content increased with the increase of the K concentration, which was due to the increase of the K content. A close relationship was observed among the osmotic potential of the solution, cumulative transpiration, and dry weight for both species among the K treatments...

Importance of Na content and water status for growth in Na-salinized rice and tomato plants

Abstract The effect of a high Na content in plant on rice (Oryza sativa L. cv. Yamabiko) and tomato (Lycopersicon esculentum Mill cv. Saturn) growth was investigated. The high Na content was achieved by the supply of NaCI (rice: R1: 40, R2: 60, R3: 80, R4: 100, R5: 120; tomato: R1′: 10, R2′: 20, R3′: 40, R4′: 60, R5′: 80 mmol( + ) kg-1) to the nutrient solution or spray of NaCl (rice: L1: 40, L2: 60, L3: 80, L4: 100, L5: 120; tomato: L1′: 10, L2′: 20, L3′: 40, L4′: 60, L5′: 80 mmol( +) kg-1) on the leaves. The high Na content in the tops suppressed the transport of K to the tops in rice and the uptake of K by the roots in tomato under N a spray conditions. The L5′ tomato leaves could not tolerate the high Na content (or lower osmotic potential (OP)) and exhibited necrosis. The N a spray resulted in a larger N a accumulation in the tops of rice and tomato than the Na supply at 2 d. This trend persisted until 8 d in tomato, but the N a supply resulted in a larger accumulation of N a in the rice tops. In the...

Some Physiological Responses of Chinese Iris to Salt Stress

Chinese iris (Iris lactea Pall. var. chinensis (Fisch) Koidz.), a robust iridaceous plant, is widespread in arid and semiarid regions with high salinity. However, the mechanism of its salt tolerance is not well understood. In this study, plant growth, water status, content and distribution of inorganic ions, cell membrane permeability, and proline content of I. lactea under salt stress were investigated using nutrient solutions with six NaCl concentrations ranging from 0 to 350 mmol L^(-1). The results indicated that the biomass, height, fresh weight, K(superscript +) content, and K(superscript +)/Na(superscript +) and Ca(superscript 2+)/Na(superscript +) ratios decreased with increasing NaCl stress, whereas plant water deficit and contents of Na(superscript +) and Cl(superscript -) increased with increasing NaC1 stress. In all salt treatments, water deficit of shunts was found to be higher than that of roots and had a positive correlation with salt concentration. When the NaCl concentration was less than 280 mmol L^(-1), the ion absorption selectivity ratio and the transportation selectivity ratio sharply increased with increasing NaC1 stress. Under medium salt stress, I. lactea exhibited a strong K(superscript +) selective absorption and the transportation of K(superscript +) from roots to shoots increased, whereas Na(superscript +) was not transported and was mostly retained in roots. The plants were able to maintain osmotic adjustment through the accumulation of Na(superscript +), Cl(superscript -), and proline. On the basis of its biomass production under salt stress, I lactea could be considered as a facultative halophyte.

Lipid Peroxidation and Antioxidative Enzymes of Two Turfgrass Species Under Salinity Stress

Abstract Salinity stress is a major factor limiting the growth of turfgrass irrigated with recycled wastewater. The change in lipid peroxidation in terms of malondialdehyde (MDA) content and the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxide (APX) and glutathione reductase (GR) in the shoots and roots of Kentucky bluegrass and tall fescue were investigated under salinity stress. Plants were subjected to 0, 50, 100, 150 and 200 mmol L−1 NaCl for 40 d. The MDA content under salinity stress was lower in tall fescue than in Kentucky bluegrass in both shoots and roots. Activities of SOD in the shoots of both species increased with salinity stress. The activities of CAT and APX decreased in Kentucky bluegrass, but no significant difference in the activities of CAT and APX was observed in tall fescue. The activities of SOD, CAT and APX in the shoots of tall fescue were higher than those in Kentucky bluegrass. In the roots of Kentucky bluegrass, SOD and GR activities increased and CAT and APX activities decreased in comparison with the control. In the roots of tall fescue, salinity increased the activities of SOD, CAT, and APX. These results suggested that tall fescue exhibited a more effective protection mechanism and mitigated oxidative stress and lipid peroxidation by maintaining higher SOD, CAT and APX activities than Kentucky bluegrass.

Adequate internal water status of NaCl-salinized rice shoots enhanced selective calcium and potassium absorption

Abstract High Na stress induces deleterious effects on plants by ion toxicity, inadequate water status and nutrient imbalances. Exogenous Ca ions that can sustain a high absorption rate of both Ca and K against Na in plants improve plant growth. To examine the effect of adequate internal water status on the process of cation absorption, water spray treatments were compared with Ca addition treatments at high (40, 80 and 120 mol m−3) NaCl concentrations. The water spray treatments improved internal water status and led to a higher Ca accumulation (73.2–85.2% increase) in the shoots than Na treatments at the same external Na and Ca concentrations. Higher Ca contents of shoots in the water spray treatments than in the corresponding Na treatments were induced by the higher transpiration stream concentration factor of Ca. Examination of plants with an adequate water status in shoots revealed that the active absorption of Ca was sensitive to the internal water status, and that there was no antagonistic effect of Na on Ca. It was necessary for the NaCl-salinized plants that Ca be actively absorbed and transported to avoid salinity damage, which was achieved through adequate water status.

Sodium tolerance of plants in relation to ionic balance and the absorption ability of microelements

Abstract Salinity stress is a major abiotic problem in arid land agriculture. In particular, Na stress severely limits crop production because it causes Na toxicity and disturbs the homeostasis of essential cations and microelements in crops. The purpose of the present study was to verify the validity of two indexes with regard to Na tolerance in plants: (1) cation balance (([K]+[Ca]+[Mg])/[Na]), (2) absorption ability of microelements. Salicornia bigelobii (highly salt tolerant), beet (tolerant), maize (moderately sensitive) and bean (sensitive) were grown in artificially prepared saline (SA), sodic (SO) and highly sodic (HSO) soils. Salicornia bigelobii showed the best growth in SO soil and accumulated Na in the growing part of the shoot. Beet showed the best growth in SA soil and also needed Na for satisfactory growth. Both species, therefore, can be classified as halophytes. There was no relationship between growth and cation balance in Salicornia bigelobii and beet. The salt treatments suppressed the growth of maize and bean, with more severe suppression in bean. The cation balance of maize was higher than that of bean. Cation balance can, therefore, be an index of Na tolerance in maize and bean, which are glycophytes. Salicornia bigelovii and beet actively absorbed microelements under high Na conditions. In maize and bean, the salt treatments lowered the uptake amount of microelements, more so in bean. Absorption ability of microelements can, therefore, be an index of Na tolerance, irrespective of whether the plants are halophytes or glycophytes.

Abscisic acid substantially inhibits senescence of cucumber plants (Cucumis sativus) grown under low nitrogen conditions.

Low nitrogen (N) availability such as that found in both dry land and tropical regions limits plant growth and development. The relationship between the level of abscisic acid (ABA) in a plant and its growth under low-N conditions was investigated. The level of ABA in cucumber (Cucumis sativus) plants under low-N conditions was significantly higher at 10 and 20 d after transplantation compared with that under sufficient-N conditions. Chlorophyll was preserved in the aerial parts of cucumber plants grown under low-N conditions in the presence of ABA, while there was no significant difference between control plants and ABA-applied plants under sufficient-N conditions. ABA suppressed the reduction of chlorophyll biosynthesis under low-N conditions but not under sufficient-N conditions. On the other hand, ABA decreased the expression of the chlorophyll degradation gene in older cucumber plants grown under both conditions. In addition, transcript and protein levels of a gene encoding a chlorophyll a/b binding protein were positively correlated with ABA concentration under low-N conditions. The chloroplasts in control plants were round, and the stack of thylakoid membranes was reduced compared with that of plants treated with ABA 10(-5) M. These results strongly suggest that ABA is accumulated in cucumber plants grown under low-N conditions and that accumulated ABA promotes chlorophyll biosynthesis and inhibits its degradation in those plants.

Responses of Halophyte Salicornia bigelovii to Different Forms of Nitrogen Source

Abstract Salt-affected soils are agricultural and environmental problems on a global scale. Plants suffer from saline stresses in these soils and show nitrogen (N) deficiency symptoms. However, halophytes grow soundly under saline conditions. In order to clarify the N nutrition of the halophyte Salicornia bigelovii , it was grown at several N levels (1, 2, 3, and 4 mmol L −1 ), supplied in the form of NO − 3 or ammonium (NH + 4 ), under high NaCl conditions (200 mmol L −1 ). NH + 4 -fed plants showed better growth than NO − 3 -fed plants at 1–3 mmol L −1 N, and plants in both treatments showed the same growth at 4 mmol L −1 N. Nitrogen contents in NO − 3 -fed plants increased with the N concentrations in solution; competitive inhibition of NO − 3 absorption by Cl − was observed under lower N conditions. In addition, shoot dry weight was significantly correlated only with shoot N content. Therefore, growth of NO − 3 -fed plants was regulated by N absorption. In contrast, N contents of shoots in NH + 4 -fed plants did not change with N concentration. Shoot Na content decreased with increasing N concentration, while K content increased. Dry weight was highly correlated only with K content in NH + 4 -fed plants. These observations indicated that growth of NH + 4 -fed plants was mainly regulated by K absorption.