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Effects of non-uniform root zone salinity on water use, Na+ recirculation, and Na+ and H+ flux in cotton.

Kong X, Luo Z, Dong H, Eneji AE, Li W - J. Exp. Bot. (2011)

Bottom Line: Non-uniform treatments decreased Na(+) concentrations in leaves.The [Na(+)] in the '0' side roots of the 0/200 treatment was significantly higher than that in either side of the 0/0 control, but greatly decreased when the '0' side phloem was girdled, suggesting that the increased [Na(+)] in the '0' side roots was possibly due to transportation of foliar Na(+) to roots through phloem.Improved plant growth under non-uniform salinity was thus attributed to increased water use, reduced leaf Na(+) concentration, transport of excessive foliar Na(+) to the low salinity side, and enhanced Na(+) efflux from the low salinity root.

View Article: PubMed Central - PubMed

Affiliation: Shandong Academy of Agricultural Sciences, Jinan, People's Republic of China.

ABSTRACT
A new split-root system was established through grafting to study cotton response to non-uniform salinity. Each root half was treated with either uniform (100/100 mM) or non-uniform NaCl concentrations (0/200 and 50/150 mM). In contrast to uniform control, non-uniform salinity treatment improved plant growth and water use, with more water absorbed from the non- and low salinity side. Non-uniform treatments decreased Na(+) concentrations in leaves. The [Na(+)] in the '0' side roots of the 0/200 treatment was significantly higher than that in either side of the 0/0 control, but greatly decreased when the '0' side phloem was girdled, suggesting that the increased [Na(+)] in the '0' side roots was possibly due to transportation of foliar Na(+) to roots through phloem. Plants under non-uniform salinity extruded more Na(+) from the root than those under uniform salinity. Root Na(+) efflux in the low salinity side was greatly enhanced by the higher salinity side. NaCl-induced Na(+) efflux and H(+) influx were inhibited by amiloride and sodium orthovanadate, suggesting that root Na(+) extrusion was probably due to active Na(+)/H(+) antiport across the plasma membrane. Improved plant growth under non-uniform salinity was thus attributed to increased water use, reduced leaf Na(+) concentration, transport of excessive foliar Na(+) to the low salinity side, and enhanced Na(+) efflux from the low salinity root.

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Split-root system used in this study, showing the schematic diagram of the graft–split-root system (A); root system of cotton exposed to uniform NaCl concentrations (equal on both root sides, such as 0/0 mM and 100/100 mM NaCl treatment) or to non-uniform NaCl concentrations (different in the low and high salt sides, such as 0/200 mM and 50/150 mM NaCl treatment) for 1, 3, and 7 d (B); the grafted plants were uniform before treatment (C); the xylem and phloem of the two halves of the hypocotyl and stem were harvested separately after treatment (D); the girdled position of the grafted cotton is shown (E). (This figure is available in colour at JXB online.)
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fig1: Split-root system used in this study, showing the schematic diagram of the graft–split-root system (A); root system of cotton exposed to uniform NaCl concentrations (equal on both root sides, such as 0/0 mM and 100/100 mM NaCl treatment) or to non-uniform NaCl concentrations (different in the low and high salt sides, such as 0/200 mM and 50/150 mM NaCl treatment) for 1, 3, and 7 d (B); the grafted plants were uniform before treatment (C); the xylem and phloem of the two halves of the hypocotyl and stem were harvested separately after treatment (D); the girdled position of the grafted cotton is shown (E). (This figure is available in colour at JXB online.)

Mentions: When most seedlings reached the two true leaf stage, uniform seedlings were carefully removed from the sand and washed with water. Split-root systems were established through grafting with these seedlings (Fig. 1). Briefly, a ‘/’ shaped incision was made with a blade on the hypocotyl 2 cm below the two cotyledons, leaving about one-third of the hypocotyl tissues intact. The top of the rootstock was cut to form a deep ‘Δ’ at the same position of the hypocotyl from another seedling. The ‘Δ’ section was then inserted into the ‘/’ incision of the plant and closely wrapped with parafilm. Grafted seedlings were transferred to plastic pots containing aerated nutrient solution, sprayed with water, and immediately covered with plastic bags to prevent wilting. The nutrient solution was topped up with deionized water as required and renewed weekly. The solution consisted of (mM): 1.25 Ca(NO3)2, 1.25 KNO3, 0.5 MgSO4, 0.25 NH4H2PO4, 0.05 EDTA-FeNa; and (μM): 10 H3BO3, 0.5 ZnSO4, 0.1 CuSO4, 0.5 MnSO4, 0.0025 (NH4)6Mo7O24, and was adjusted to pH 6 with KOH. When a new leaf emerged from the grafted seedling at 2 weeks after grafting, the plastic bag and parafilm were removed. Grafted seedlings with two uniform split-root systems were transferred to a naturally lit greenhouse to grow under 28–32/20–24 °C and 60–70% relative humidity for 20 d. Nutrient solutions were renewed daily during the period of growth. Healthy seedlings with two uniform split-root systems (Fig. 1B, C) were selected for further experiments.


Effects of non-uniform root zone salinity on water use, Na+ recirculation, and Na+ and H+ flux in cotton.

Kong X, Luo Z, Dong H, Eneji AE, Li W - J. Exp. Bot. (2011)

Split-root system used in this study, showing the schematic diagram of the graft–split-root system (A); root system of cotton exposed to uniform NaCl concentrations (equal on both root sides, such as 0/0 mM and 100/100 mM NaCl treatment) or to non-uniform NaCl concentrations (different in the low and high salt sides, such as 0/200 mM and 50/150 mM NaCl treatment) for 1, 3, and 7 d (B); the grafted plants were uniform before treatment (C); the xylem and phloem of the two halves of the hypocotyl and stem were harvested separately after treatment (D); the girdled position of the grafted cotton is shown (E). (This figure is available in colour at JXB online.)
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3295398&req=5

fig1: Split-root system used in this study, showing the schematic diagram of the graft–split-root system (A); root system of cotton exposed to uniform NaCl concentrations (equal on both root sides, such as 0/0 mM and 100/100 mM NaCl treatment) or to non-uniform NaCl concentrations (different in the low and high salt sides, such as 0/200 mM and 50/150 mM NaCl treatment) for 1, 3, and 7 d (B); the grafted plants were uniform before treatment (C); the xylem and phloem of the two halves of the hypocotyl and stem were harvested separately after treatment (D); the girdled position of the grafted cotton is shown (E). (This figure is available in colour at JXB online.)
Mentions: When most seedlings reached the two true leaf stage, uniform seedlings were carefully removed from the sand and washed with water. Split-root systems were established through grafting with these seedlings (Fig. 1). Briefly, a ‘/’ shaped incision was made with a blade on the hypocotyl 2 cm below the two cotyledons, leaving about one-third of the hypocotyl tissues intact. The top of the rootstock was cut to form a deep ‘Δ’ at the same position of the hypocotyl from another seedling. The ‘Δ’ section was then inserted into the ‘/’ incision of the plant and closely wrapped with parafilm. Grafted seedlings were transferred to plastic pots containing aerated nutrient solution, sprayed with water, and immediately covered with plastic bags to prevent wilting. The nutrient solution was topped up with deionized water as required and renewed weekly. The solution consisted of (mM): 1.25 Ca(NO3)2, 1.25 KNO3, 0.5 MgSO4, 0.25 NH4H2PO4, 0.05 EDTA-FeNa; and (μM): 10 H3BO3, 0.5 ZnSO4, 0.1 CuSO4, 0.5 MnSO4, 0.0025 (NH4)6Mo7O24, and was adjusted to pH 6 with KOH. When a new leaf emerged from the grafted seedling at 2 weeks after grafting, the plastic bag and parafilm were removed. Grafted seedlings with two uniform split-root systems were transferred to a naturally lit greenhouse to grow under 28–32/20–24 °C and 60–70% relative humidity for 20 d. Nutrient solutions were renewed daily during the period of growth. Healthy seedlings with two uniform split-root systems (Fig. 1B, C) were selected for further experiments.

Bottom Line: Non-uniform treatments decreased Na(+) concentrations in leaves.The [Na(+)] in the '0' side roots of the 0/200 treatment was significantly higher than that in either side of the 0/0 control, but greatly decreased when the '0' side phloem was girdled, suggesting that the increased [Na(+)] in the '0' side roots was possibly due to transportation of foliar Na(+) to roots through phloem.Improved plant growth under non-uniform salinity was thus attributed to increased water use, reduced leaf Na(+) concentration, transport of excessive foliar Na(+) to the low salinity side, and enhanced Na(+) efflux from the low salinity root.

View Article: PubMed Central - PubMed

Affiliation: Shandong Academy of Agricultural Sciences, Jinan, People's Republic of China.

ABSTRACT
A new split-root system was established through grafting to study cotton response to non-uniform salinity. Each root half was treated with either uniform (100/100 mM) or non-uniform NaCl concentrations (0/200 and 50/150 mM). In contrast to uniform control, non-uniform salinity treatment improved plant growth and water use, with more water absorbed from the non- and low salinity side. Non-uniform treatments decreased Na(+) concentrations in leaves. The [Na(+)] in the '0' side roots of the 0/200 treatment was significantly higher than that in either side of the 0/0 control, but greatly decreased when the '0' side phloem was girdled, suggesting that the increased [Na(+)] in the '0' side roots was possibly due to transportation of foliar Na(+) to roots through phloem. Plants under non-uniform salinity extruded more Na(+) from the root than those under uniform salinity. Root Na(+) efflux in the low salinity side was greatly enhanced by the higher salinity side. NaCl-induced Na(+) efflux and H(+) influx were inhibited by amiloride and sodium orthovanadate, suggesting that root Na(+) extrusion was probably due to active Na(+)/H(+) antiport across the plasma membrane. Improved plant growth under non-uniform salinity was thus attributed to increased water use, reduced leaf Na(+) concentration, transport of excessive foliar Na(+) to the low salinity side, and enhanced Na(+) efflux from the low salinity root.

Show MeSH