秸秆还田是干旱地区广泛应用的作物高效生产技术，但其能否通过改善作物生理生态特性而进一步提高产量还需实践验证。在甘肃河西绿洲灌区，通过田间试验，研究了不同秸秆还田方式[免耕秸秆覆盖还田(NTSM)、免耕秸秆立茬还田(NTSS)、传统翻耕秸秆还田(CTS)及传统翻耕无秸秆还田(CT, 对照)对小麦生理生态特性的调控效应，以期阐明秸秆还田影响小麦产量的生理生态机制。结果表明，NTSM和NTSS处理对小麦生理生态特性的调控作用优于CTS和CT而获得较高产量，NTSM因较优的调控效应使其增产幅度略高于NTSS。与CT相比，NTSM降低了小麦孕穗期之前的叶面积指数为6.1–7.6%，提高孕穗期之后的叶面积指数为38.9–45.1%，NTSM可有效地调控小麦光合源动态。NTSM较CT提高小麦灌浆期与蜡熟期光合速率为10.2–21.4%与11.0–21.6%，提高蒸腾速率为4.4–10.0%与5.3–6.1%，提高叶片水分利用效率为5.6–10.4%与5.4–14.6%。与CT相比，NTSM提高小麦抽穗期至蜡熟期叶片与土壤水势分别为7.5–12.0%与8.9–24.0%。NTSM较CT降低了小麦叶-土水势差，表明NTSM处理有利于保持干旱条件下小麦植株水分需求和土壤水分供给的稳定性。NTSM较CT增产18.6~27.3%，其增产归因于穗数、穗粒数和千粒重的协同增加。因此，免耕秸秆覆盖还田是干旱灌区优化小麦生理生态特性及获得高产的可行栽培措施。

A hydroponic study was conducted to determine the effects of selenium (Se: 0, 3, 6 μmol L−1) on senescence-related oxidative stress in garlic plants grown under two sulfur (S) levels. We evaluated the yields of plants harvested at 160 and 200 days after sowing. Plants grown under a low Se dose (0.3 μmol L−1) at low S level showed higher yields (12.0% increase in fresh weight yield, 13.7% increase in dry weight yield) than the controls, despite a decrease in chlorophyll concentration. Compared with control plants, the Se-treated plants showed lower levels of lipid peroxidation. The Se-treated plants also showed higher activities of glutathione peroxidase and catalase, but lower superoxide dismutase activities. Changes in Fv/Fm values and proline contents were affected more strongly by S than by Se. On the basis of our results, we can conclude that Se plays a key role in the antioxidant systems in garlic seedlings. It delays senescence by alleviating the peroxide stress, but it can be toxic at high levels. A high S level may increase tolerance to high Se concentrations through reducing Se accumulation in plants.