Water is a key limiting factor in agriculture.  Water resource shortages have become a serious threat to global food security.  The development of water-saving irrigation techniques based on crop requirements is an important strategy to resolve water scarcity in arid and semi-arid regions.  In this study, field experiments with winter wheat were performed at Wuqiao Experiment Station, China Agricultural University in two growing seasons in 2013–2015 to help develop such techniques.  Three irrigation treatments were tested: no-irrigation (i.e., no water applied after sowing), limited-irrigation (i.e., 60 mm of water applied at jointing), and sufficient-irrigation (i.e., a total of 180 mm of water applied with 60 mm at turning green, jointing and anthesis stages, respectively).  Leaf area index (LAI), light transmittance (LT), leaf angle (LA), transpiration rate (T_r), specific leaf weight, water use efficiency (WUE), and grain yield of winter wheat were measured.  The highest WUE of wheat in the irrigated treatments was found under limited-irrigation and grain yield was only reduced by a small amount in this treatment compared to the sufficient irrigation treatment.  The LAI and LA of wheat plants was lower under limited irrigation than sufficient irrigation, but canopy LT was greater.  Moreover, the specific leaf weight of winter wheat was significantly lower under sufficient than limited irrigation conditions, while the leaf T_r was significantly higher.  Correlation analysis showed that the increased LAI was associated with an increase in the leaf T_r, but the specific leaf weight had the opposite relationship with transpiration.  Optimum WUE occurred over a reasonable range in leaf T_r.  In conclusion, reduced irrigation can optimize wheat canopies and regulate water consumption, with only small reductions in final yield, ultimately leading to higher wheat WUE and water saving in arid and semi-arid regions.

Compared to single-trait transgenic crops, stacked transgenic plants may be more prone to become weedy, and transgene flow from stacked transgenic plants to weedy relatives may pose a potential environmental risk because these hybrids could be more advantageous under specific environmental conditions.  Evaluation of the potential environmental risk caused by stacked transgenes is essential for assessing the environmental consequences caused by crop-weed transgene flow.  The agronomic performance of fitness-related traits was assessed in F₁+ (transgene positive) hybrids (using the transgenic line T1c-19 as the paternal parent) in monoculture and mixed planting under presence or absence glufosinate pressure in the presence or absence of natural insect pressure and then compared with the performance of F₁– (transgene negative) hybrids (using the non-transgenic line Minghui 63 (MH63) as the paternal parent) and their weedy rice counterparts.  The results demonstrated that compared with the F₁– hybrids and weedy rice counterparts, the F₁+ hybrid presented higher performance (P<0.05) or non-significant changes (P>0.05) under natural insect pressure, respectively, lower performance (P<0.05) or non-significant changes (P>0.05) in the absence of insect pressure in monoculture planting, respectively.  And compared to weedy rice counterparts, the F₁+ hybrid presented higher performance (P<0.05) or non-significant changes (P>0.05) in the presence or absence of insect pressure in mixed planting, respectively.  The F₁+ hybrids presented non-significant changes (P>0.05) under the presence or absence glufosinate pressure under insect or non-insect pressure in monoculture planting.  The all F₁+ hybrids and two of three F₁– hybrids had significantly lower (P<0.05) seed shattering than the weedy rice counterparts.  The potential risk of gene flow from T1c-19 to weedy rice should be prevented due to the greater fitness advantage of F₁ hybrids in the majority of cases.