干旱区生态环境知识资源中心

The purpose of this study was to examine the uptake and distribution of ions in three grain legume species for potential use in and zones. Tepary bean (Phaseolus acutifolius A. Gray), cowpea (Vigna unguiculata L. Walp.), and wild bean "frijolillo" (Phaseolus filiformis Bent) were grown during a period of 14 d in a nutrient solution salinized with 80 mmol L-1 NaCl. Plant height, leaf number, and leaf area of the saline treated plants were all low because of salinity. The dry weight (DW) of the roots, stems, and leaves of cowpea and "frijolillo" was significantly lower when the plants were subjected to the saline treatment, while the DW of the stems and leaves of the tepary bean plants treated with NaCl was close to that of the control plants (0 mmol L-1 NaCl). Root DW was significantly higher under salinity conditions only in tepary bean. The net uptake rate (NUR) and net transport rate (NTR) of Ca2+, Mg2+, and K+ in cowpea and "frijolillo" shoots were lower in the saline treated plants than in the control (0 mmol L-1 NaCl), while tepary bean subjected to the salinity treatment displayed higher cation net uptake rate and transport. The NTR / NUR ratio of Na+ in tepary bean, "frijolillo," and cowpea treated with NaCl were 0.07, 0.70 and 0.72, respectively, indicating that Na+ transport to the shoots was in the following order: cowpea > "frijolillo" > tepary bean. Na+ distribution to roots, stems, and petioles was higher than the DW distribution to the same organs of the saline-treated plants only for tepary bean, while the Na+ distribution was lower than the DW distribution to leaves. These facts indicate that Na+ ion easily move to the leaves in cowpea, while in tepary bean and "frijolillo," Na+ mobility is restricted in order to prevent Na+ accumulation in leaves, and is achieved through the higher capacity of the stem and petiole to hold Na+. In the cowpea and "frijolillo" plants treated with NaCl, the uptake and transport of Ca2+ and Mg2+ were significantly lower, while in the tepary bean plants these rates were not affected by the saline treatment that exerted a negligible adverse effect on plant growth. The higher Ca2+ and Mg2+ uptake in tepary bean could be caused either by the higher Ca2+ and Mg2+ absorption efficiency or by the higher Ca2+ and Mg2+ uptake and transport required to neutralize excess Cl- in the cells.