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Experiments were carried out with barley cultivars (Hordeum vulgare L.) grown in both pot‐ and water‐culture. Net uptake of NO3− and K+ in the roots was followed in two barley cultivars grown on water‐culture for 85 days. After an initial period of low net uptake of both ions, uptake increased until a maximum was reached after 30 to 45 days. Thereafter, net uptake of NO3− and K+ steadily decreased. In the pot experiments, effects of different mineral supply on day 4 to 18 upon the development of five barley cultivars of various earliness were investigated. The effect of earliness on fresh weight production was largest when mineral supply on day 4 to 18 was limited. The influence of limited mineral supply on day 4 to 18 on K‐economy was independent of earliness of the cultivars. The maximal N‐content was reached at the same time as maximal fresh and dry weight in fairly late cultivars; in early cultivars maximum N‐level was reached later than maximum fresh and dry weight. Overall, maximal N‐content was higher in the fairly late cultivars than in the early cultivars. The highest rate of 15N‐transport was attained later in two of three fairly late cultivars than in early cultivars. Partitioning of dry weight, N and K in the shoots changed during ageing, ears being an important sink. Varietal differences in partitioning depended on the earliness of the cultivars. The largest fraction of recently supplied 15N, supplied as nitrate, and K+ (86Rb) were found in the stems. In the oldest plants of the early cultivars the transport to the ears of these isotopes was gradually impaired, reflecting the decreasing function of the long distance transport system.

Six cultivars of spring barley (Hordeum vulgare L. cvs Salve, Nümberg II, Bomi, Risø 1508, Mona and Sv 73 608) were grown in water culture for three weeks with various combinations of mineral supply and differential roots/shoot temperatures during the growth period. Most important for growth and accumulation of N, K+, Ca2+ and Mg2+ was the mineral supply, followed by the root temperature and the choice of cultivar. Treatments with low mineral supply or low root temperature induced a uniform reduction in growth and accumulation of the ions studied. The effects of low mineral supply and low root temperature on growth and N accumulation was additive, which indicates that these factors exert their influence independently of each other. Roots grown at 10°C were smaller and Rb+(86Rb) influx was higher than in roots grown at 20°C. It is suggested that the control of Rb+(86Rb) influx is affected by the root temperature and the age of the plants. The higher 86Rb+ (86Rb) influx into the low temperature roots could not compensate for the smaller root size. However, the lower total mineral accumulation made up for the needs of the smaller plants and cannot explain the reduction in growth.

Growth and uptake of N, P, S, K, Ca and Mg in barley (Hordeum vulgare L.) were studied in water culture using young plants of 17 cultivars. Large varietal differences were obtained in dry weight production and mineral accumulation. The differences were not the same for plants grown in high‐ and low‐salt media. For plants grown under both conditions there was a good correlation between dry weight production and total N content. Total shoot contents of K and Ca were closely correlated with shoot dry weight. Utilization of P and S in high‐ and low‐salt plants and Mg in low‐salt plants was variable in relation to dry weight production in both types of nutrient conditions. The correlation between dry weight and total content of Mg in high‐salt plants was good. These differences in mineral economy between young barley plants were partly caused by varietal differences in relative growth rate, and in high‐salt seedlings also by differences in seed content of N. The significance of root size, and of uptake, root‐shoot partitioning and use‐efficiency of specific elements differed; all four factors were important for P and S, but had varying impact on K, Mg and Ca. For N, differences in root size and ion accumulation were the most important factors causing varietal variation in mineral nutrition. – In a special experiment seedlings of barley were transferred to N‐free nutrient solution after six days of adequate N supply. There was no significant varietal differences in use‐efficiency ratio of N. Root/shoot partitioning of N was unaffected.

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