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Many physiological mechanisms associated with nutrient supply have been implicated as improving plant growth under drought conditions. However, benefits to plant growth under drought might derive from an increased recovery of soil water through osmotic adjustment in the shoots and especially in the roots. Thus, experiments were carried out to investigate the effects of the nutrients N, P and K applied singly or in combination, on the osmotic adjustment and turgor maintenance in the roots and leaves of maize seedlings. The seedlings were harvested between 18 and 37 days after sowing according to the soil matric threshold potentials. Soil matric potentials and shoot and root biomass were determined at harvest. Turgor pressure and osmotic adjustment of the leaves and roots were estimated by measurements of their water and osmotic potentials. Results showed that plants with either of the combined fertilisation treatments NPK or NP grew faster at a given level of drought stress than those with no fertilisation, N, P or K applied individually or the combined nutrient treatments PK and NK. Among the fertiliser applications with either a single or two combined nutrients, plants treated with any of N, P or NP grew faster than those with either K or NK. The association between the interactive effects of nutrients and drought stress on the osmotic adjustment and turgor maintenance in roots may partially explain the role of nutrients in drought tolerance of maize seedlings. In particular, the roots exhibited a higher osmotic adjustment than the leaves for all nutrient treatments, suggesting that shoot growth shows a higher sensitivity to water deficit compared to root growth. We conclude that the maintained turgor of roots under drought stress obtained with an optimal nutrient supply results in better root growth and apparently promotes overall plant growth, suggesting that osmotic adjustment is an adaptation not only for surviving stress, but also for growth under such conditions.

Salinity is increasingly limiting the production of graminaceous crops constituting the main sources of staple food (rice, wheat, barley, maize and sorghum), primarily through reductions in the expansion and photosynthetic yield of the leaves. In the present review, we summarise current knowledge of the characteristics of the spatial distribution patterns of the mineral elements along the growing grass leaf and of the impact of salinity on these patterns. Although mineral nutrients have a wide range of functions in plant tissues, their functions may differ between growing and non-growing parts of the grass leaf. To identify the physiological processes by which salinity affects leaf elongation in non-halophytic grasses, patterns of mineral nutrient deposition related to developmental and anatomical gradients along the growing grass leaf are discussed. The hypothesis that a causal link exists between ion deficiency and / or toxicity and the inhibition of leaf growth of grasses in a saline environment is tested.

In this study, we quantified the spatial distributions of inorganic ions and sugars contributing to osmotic adjustment and their net deposition rates in the elongating and mature zones of leaf 4 of the main stem of spring wheat (Triticum aestivum L. cv. Lona) during its linear growth phase under saline soil conditions. Plants were grown in growth chambers in soil irrigated/treated with nutrient solution containing either no added or 120 mM NaCl. The sampling was conducted on the 3rd day after emergence of leaf 4 at 3 and 13 h into the 16 h photoperiod. The patterns of spatial distributions of total osmoticum, cation, anion and sugar contents (mmol kg-1 H2O) were distinct and were affected by salinity. The total osmoticum content in the region between 0 and 60 mm above the leaf base differed between the two harvests at 120 mM NaCl. Net deposition rates of total osmotica, cations, anions, and sugars (mmol kg-1 H2O h-1) in both treatments increased from the base of the leaf to the most actively elongating location and then decreased near the end of the elongation zone. Contributions of cations, anions, and sugars to osmotic adjustment varied with distance from the leaf base, and were about 21–30, 15–21, and 13%, respectively, in the elongation zone. We suggest that the accumulation of solutes under saline conditions occurs both by increasing the net deposition rate of osmotica and by reducing growth.