Growth and contents of sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), chloride (Cl), phosphorus (P) and sulphur (S) in shoot and root tissues of Carthamus fincforius plants were measured at combinations of four nutrient solution osmotic potentials (Q'S = 0, -0.3, -0.6 and -0.9 MPa) induced by NaCl and CaCl treatments, three constant temperatures (T) ranging from 15 to 35 "C and four abscisic acid (ABA) concentrations (0,10,50 and 100 mg L-l). Unstressed and stressed plants grown in optimal temperature conditions (25 "C) maintained higher growth rates (dry mass production) than plants grown under low and high temperatures (15 and 35 "C respectively). Shoot and root growth (dry mass production) were largely inhibited by salinity but the magnitude of growth inhibition was temperature dependent. Safflower plants respond to salinity stress by increases in Ca, Cl and to a lesser extent Na in their shoots and roots and by a decrease in the ratio of fresh to dry weight. The ratio of WNa was decreased progressively on salinization. With stressed plants, ABA application reduced the toxicity of salt treatment, improved K uptake under salinity, effectively increased WNa ratio and helped the plants to avoid Na toxicity and sometimes enhanced growth. The effect of ABA on the growth was more pronounced at optimum temperature (25 "C). The association between the internal mineral element concentrations was largely affected by ABA application and temperature change but a wide fluctuation in response was noticed. The effects of single factors (Q',, T and ABA) on the growth and mineral contents were statistically significant. Also, bifactorial (!p, x T, @s x ABA and T x ABA) and three factorial (qs x T x ABA) interactions significantly affected the parameters. Further statistical treatment of the data (coefficient of determination n*) led to four important findings: (1) Salinity (Q',) was dominant in affecting Ca and Cl contents in both shoot and root as well as root Na content. (2) Temperature (T) had a dominant effect on growth, shoot K, Mg, P, S and root P, and S contents (3) The share of 9, x T x ABA interaction was dominant for root Na and Mg contents. (4) The single factors and their interactions had a dual role in their subsidiary effects.Abbreviations.-ABA = abscisic acid; Q's = osmotic potential, v2 = coefficient of determination; Ewt = fresh weight; d.m. = dry matter; T = temperature; MPa = mega Pascal, SAR = sodium adsorption ratio; P = phosphorus; S = sulphur 1. Introduction important component of biological responses to environmental factors. Among the environmental factors The regulation of plant growth depends on environwhich control growth and development, two are of mental factors such as light, temperature, water and special interest for crop production: water supply and nutrient supply, and the concentration and interactemperature. tion of endogenous plant hormones. Coincidence of Excessive salinity is a stress factor that negatively optimal levels of two or more factors certainly is an affects the perf...
