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To understand the effects of salinity stress on four different growth stages of sorghum, a greenhouse experiment with 10 treatments, considering all possible combinations of salinity stress and salt- free periods was carried out. The four growth stages for stress application included: emergence until growing point differentiation, growing point differentiation until half bloom, half bloom until soft dough, and soft dough until physiological maturity. Treatments were arranged based on randomized complete block design with 3 replications at the Research Greenhouse of theFerdowsiUniversityofMashhadin 2010-2011. Salinity stress during early growth and panicle differentiation declined the plant height and tiller number. The highest biological yield was obtained from the control treatment, but it was the lowest when plants were salinized throughout the growing season. When plants were stress-free at 2-3 early stages and then subjected to salt stress, reductions in total dry matter were remarkably less than those experienced when salinity was imposed in later growth stages, especially if salinity occurred at a late individual stage. Continuation of salt stress from emergence to both blooming and soft dough stages led to remarkably adverse effects on grain yield. The effect of salinity appears to be most effective on yield components that are growing or developing at the time the salt stress is imposed. The critical period of salinity stress for biological yield was more distinct than that of the grain yield. This indicates that sorghum is not sensitive to salinity at seed setting and seed filling periods.

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Second-language (L2) acquisition is generally thought to be constrained by maturational factors that circumscribe a critical period for native-like attainment. Consistent with the maturational view are age effects among learners who begin L2 acquisition prior to, but not after, closure of the putative critical period. Some studies indicate that native-like acquisition of a second language by learners after critical period rarely happens. Some subsequent studies do not support the critical period account of L2 acquisition constraints, however. Accordingly, this study was undertaken to investigate the impacts of maturational constraints on native-like attainment of second language accent, pronunciation, and intonation by Iranians who spent some years in English-speaking countries. The performance of 120 Iranian late and early arrivals was evaluated using a 6 point semantic differential scale. Descriptive and inferential statistics (independent sample t-test and ANOVA) were run (p≤ .05) to analyze the data. In keeping with other researchers, the results of the study indicate that L2 native-like attainment is constrained by the age of language learners. The results also indicate that late language learners who lived in an English-speaking country acquired near native-like proficiency whereas the late language learners who lived just in Iran were not able to acquire near native-like pronunciation. We also found modest evidence of native-like attainment among late learners.