Maximizing the utilization of water unit is of paramount importance in arid zones and worldwide. This is even more significant when plants are subjected to both thermal and water stress. Hence, a two-year (2014 and 2015 seasons) field trial was carried out to study the effect of three sowing dates (April 21, May 21, and June 21); two irrigation levels (I100 and I85) and two ascorbic acid rates, ASA (0 and 450 mg L⁻¹), on physiological and biochemical traits, productivity and water use efficiency (WUE) of sunflower. Results showed that subjecting sunflower plants to water deficit under any sowing date caused decreases in chlorophyll, carotenoids, oil% and seed yield and an increase in proline content. As averages of the two seasons, ASA treated plants caused increases in seed yield amounted to 11.7%, 10.6% and 8.4% with I100 and 5.1%, 14.4% and 7.7% with I85 compared to non-treated plants sown in April, May and June, respectively. In ASA treated plots, WUE values of sowing in April x I100 or sowing in June x I85 in 2014 and sowing in May x I85 in 2015 were as similar as that of conventional practice (sowing in May x I100 × 0 mg L⁻¹ ASA). Accordingly, results clarify that ASA can be used successfully in sunflower management programs, particularly under abiotic stresses e.g. unfavorable heat and drought.

在干旱地区和全球范围内，最大限度地利用水单元至关重要。当植物同时遭受热和水分胁迫时，这一点甚至更为重要。因此，进行了为期两年（2014年和2015年）的田间试验，以研究三个播种日期（4月21日，5月21日和6月21日）的影响。两个灌溉水平（I100和I85）和两个抗坏血酸比率ASA（0和450 mg L ^-1），向日葵的生理和生化特性，生产力和水分利用效率（WUE）。结果表明，在任何播种日期下使向日葵植物缺水都会导致叶绿素，类胡萝卜素，油含量和种子产量下降，脯氨酸含量增加。作为两个季节的平均值，与4月，5月和5月播种的未处理植物相比，用I100处理的ASA处理植物引起的种子产量分别增加11.7％，10.6％和8.4％，使用I85引起的种子产量分别增加5.1％，14.4％和7.7％。六月。在ASA处理的样地中，4月播种x I100的播种的WUE值或2014年6月x I85播种和2015年5月x I85播种的WUE值与常规做法相似（5月播种x I100×0 mg L ^-1作为一个）。因此，结果表明，ASA可以成功地用于向日葵管理计划，特别是在非生物胁迫（例如不利的高温和干旱）下。