Ion uptake and growth of wheat seedlings treated with nitrite at different pH values.

Increasing concentrations of NaNO2 caused decreases in the uptake of K+, Na+ and SO4(2-) by wheat roots at pH 4. At pH 6 or 7, the detrimental effect was much less. The translocation of nutrients to the shoots was also impaired. The root growth was strongly inhibited by increasing NaNO2 concentrations, but the shoot development was little affected. At low pH, however, the inhibitory effect was much higher.

Effects of nitrite and sulfate on K+ uptake and growth of wheat and cucumber seedlings.

The uptake of K+ ion was studied in the roots of wheat (Triticum aestivum L. cv. GK Szeged) and cucumber (Cucumis sativus L. cv. Budai csemege) seedlings grown in nutrient solution under nitrite and sulfate stress conditions. Seedlings pretreated with 1 or 10 mM NaNO2 absorbed more K+(86Rb) than those treated with 0.1 mM NaNO2. However, the posteffect was influenced considerably by Na2SO4 treatment. The results suggest that at least a partial feed-back regulation of K+ uptake may occur. However, due to the high Na+ content of the roots and the possible toxicity of NO2-, effects of Na+ and NO2- in this process cannot be excluded. The dry matter yields of the roots and shoots were strongly influenced by the NO2- supply of the plants. However, appreciable differences were observed between wheat and cucumber seedlings. The optimal SO4(2-) and NO2- concentrations of the growth solution for maximal growth differed considerably for the two species, and also for the roots and shoots in a given species. The root growth was strongly inhibited by increasing NO2- concentrations, but the shoot development was favourably affected, indicating that plants can assimilate NO2- taken up by the roots.

Effects of sodium chloride stress and calcium supply on growth, potassium uptake, and internal chloride and sodium levels of winter wheat seedlings.

The effects of saline conditions on the K+ (86Rb), Na+ and Cl- uptake and growth of 6-day-old wheat (Triticum aestivum L. cv. GK Szeged) seedlings were studied in the absence and presence of Ca2+. It was found that on direct NaCl treatment the K+ uptake of the roots in the absence of Ca2+ declined significantly with increasing salinity. The reverse was true, however, in the case of NaCl pretreatment: seedlings grown under highly saline conditions (50 mM NaCl) absorbed more K+ than those pretreated with low levels of NaCl (1 or 10 mM NaCl). The data indicate a definite Na(+)-induced K+ uptake inhibition and/or feed-back regulation in the K+ uptake of roots under the above-mentioned growth conditions. As regards the Ca2+ effect, it was established that supplemental Ca2+ counteracts the unfavourable effect of saline conditions as concerns both the K+ uptake of the roots and the dry matter yield of the seedlings. The internal concentrations of Na+ and Cl- in the seedlings increased in proportion to increasing salinity. Marked differences were experienced, however, in the internal concentrations of Na+ and Cl- in the roots and shoots, respectively. It was concluded that under these experimental conditions the salt tolerance of wheat could be related to its capability of restricting the transport of Na+ at low and moderate levels to the shoots, where it is highly toxic.