长江流域旱地多熟模式水分供需平衡特征与水分生产效益

长江流域年内降雨分布不均,季节性干旱问题严重,构建以避旱减灾为主体的多熟间套作种植模式是实现本区域水资源高效利用的根本途径。本研究于2016—2020年在长江流域(四川、湖北、湖南、江西、江苏等5个地区)进行旱地多熟模式水分利用特征评比试验,分别设置为四川:小麦-夏玉米(C1)、小麦-夏玉米‖夏大豆(C2)、饲草油菜-春玉米/夏大豆(C3)、马铃薯-春玉米/夏大豆(C4);湖北:油菜-夏玉米‖夏大豆(B1)、饲草油菜-春玉米‖春大豆(B2)、马铃薯/春玉米/夏大豆(B3);湖南:油菜-夏玉米‖夏大豆(N1)、饲草油菜-春玉米/夏大豆(N2)、饲草油菜-春玉米‖春大豆-秋大豆(N3);江西:马铃薯/春玉米/夏大豆(X1)、油菜-夏玉米‖夏大豆(X2)、黑麦草-春玉米/夏大豆(X3)、黑麦草-春玉米‖春大豆(X4);江苏:小麦-鲜食玉米/鲜食玉米(S1)、小麦-鲜食玉米/鲜食大豆(S2)、鲜食蚕豆/鲜食玉米-鲜食玉米(S3)、鲜食蚕豆/鲜食玉米-鲜食大豆(S4)。应用AquaCrop模型比较了不同种植模式的水分供需平衡特征、折谷总产量和单方水效益。4年结果表明,四川C4的水分满足率较C1、C2和C3平均分别增加5.28%、2.91%和6.00%,折谷总产量分别显著增加71.2%、49.3%和25.6%,单方水效益分别增加329.29%、123.42%和45.52%;湖北B3的水分满足率较B1和B2平均分别增加3.99%和3.51%,折谷总产量分别显著增加36.8%和25.8%,单方水效益分别增加295.60%和69.01%;湖南N2的水分满足率较N1和N3平均分别增加9.08%和2.93%,单方水效益分别增加58.47%和183.33%;江西X1的水分满足率较X2、X3和X4平均分别增加7.94%、6.70%和4.05%,折谷总产量分别显著增加112.4%、152.5%和116.8%,单方水效益分别增加70.13%、15.49%和46.53%;江苏S4的水分满足率较S1、S2和S3平均分别增加8.93%、5.85%和2.96%,折谷总产量分别显著增加35.4%、17.5%和12.6%,单方水效益分别增加60.25%、14.93%和45.56%。四川、湖北、湖南、江西和江苏分别种植马铃薯-春玉米/夏大豆、马铃薯/春玉米/夏大豆、饲草油菜-春玉米/夏大豆、马铃薯/春玉米/夏大豆和鲜食蚕豆-鲜食玉米/鲜食大豆等种植模式,有利于改善水分供需平衡特征,提高折谷总产量和单方水效益。长江流域旱地应根据不同的降雨条件选择适宜的多熟间套作种植模式,以实现避旱减灾和水资源高效利用。

Response of Nitrate Metabolism in Seedlings of Oilseed Rape(Brassica napus L.) to Low Oxygen Stress

In order to understand the response of nitrate metabolism in seedlings of oilseed rape （Brassica napus L.） to low oxygen stress （LOS）, two cultivars were studied at different light, LOS time and exogenous nitrate concentrations under hydroponic stress. Results show that N-uptake and dry matter of rape seedlings were decreased after LOS stress while nitrate accumulation （NA） under LOS was induced by darkness. Nitrate accumulation peaked at 3 d while root activity （RA, deifned as dehydrogenase activity） decreased with prolonged waterlogging exposure. Exogenous nitrate signiifcantly elevated NA and RA. Tungstate （TS） and LOS inhibited nitrate reductase （NR） activity while NR transcription and activity were enhanced by exogenous nitrate. Low oxygen stress stimulated the activity of superoxide dismutase （SOD） and peroxidase （POD） slightly, but inhibited that of catalase （CAT）. B. napus L. Zhongshuang 10 （ZS10）, a LOS tolerant cultivar, displayed smaller decrease upon dry matter under LOS, higher NA in darkness and lower NA in light than B. napus L. Ganlan CC （GAC）, a LOS sensitive variety. ZS10 had lower NA and higher RA after waterlogging and exogenous nitrate treatment, and higher NR activity under TS inhibition than GAC, but the activity of antioxidant enzymes did not change under LOS. The results indicate that nitrate metabolism involved tolerance of rape seedlings to LOS, with lower accumulation and higher reduction of nitrate being related to higher LOS tolerance of rape seedlings exposed to waterlogging.

Identification of suitable reference genes in leaves and roots of rapeseed (Brassica napus L.) under different nutrient deficiencies

Nutrient deficiency stresses often occur simultaneously in soil. Thus, it＇s necessary to investigate the mechanisms underlying plant responses to multiple stresses through identification of some key stress-responsive genes. Quantitative real-time PCR （qRT-PCR） is essential for detecting the expression of the interested genes, of which the selection of suitable reference genes is a crucial step before qRT-PCR. To date, reliable reference genes to normalize qRT-PCR data under different nutrient deficiencies have not been reported in plants. In this study, expression of ten candidate reference genes was detected in leaves and roots of rapeseed （Brassica napus L.） after implementing different nutrient deficiencies for 14 days. These candidate genes, included two traditionally used reference genes and eight genes selected from an RNA- Seq dataset. Two software packages （GeNorm, NormFinder） were employed to evaluate candidate gene stability. Results showed that VHA-E1 was the highest-ranked gene in leaves of nutrient-deficient rapeseed, while VHA-G1 and UBC21 were most stable in nutrient-deficient roots. When rapeseed leaves and roots were combined, UBC21, HTB1, VHA-G1 and A CT7 were most stable among all samples. To evaluate the stabilities of the highest-ranked genes, the relative expression of two target genes, BnTrxl;1 and BnPhtl;3 Were further determined. The results showed that the relative expression of BnTrxl;1 depended on reference gene selection, suggesting that it＇s necessary to evaluate the stability of reference gene prior to qRT-PCR. This study provides suitable reference genes for gene expression analysis of rapeseed responses to different nutrient deficiencies, which is essential for elucidation of mechanisms underlying rapeseed responses to multiple nutrient deficiency stresses

稻秸还田方式对酸性和碱性土壤养分含量、微生物数量及油菜生长的影响

本研究于2017~2018年在中国农业科学院油料作物研究所网室,以油菜为供试作物,用土培盆栽的方法,设秸秆不还田(对照)、秸秆焚烧后灰烬与土壤混匀还田、秸秆粉碎与土壤混匀还田、秸秆粉碎覆盖还田4个处理,研究稻秸还田方式对酸、碱性土壤养分形态与含量、微生物数量和油菜生长的影响,以期选出适合酸、碱性土壤的稻秸还田方式。结果表明:(1)稻秸还田方式对油菜各生育时期土壤速效养分含量影响显著。土壤碱解氮、有效磷和速效钾的含量以秸秆粉碎与土壤混匀还田处理增加最多,该处理成熟期在酸性土壤上比对照、秸秆焚烧后灰烬与土壤混匀还田和秸秆粉碎覆盖还田处理各养分平均分别增加48%、10%和47%。(2)4种稻秸还田方式对土壤真菌、细菌、放线菌的数量变化均产生影响,但是秸秆粉碎与土壤混匀还田在酸性土壤上促进真菌数量的增加,该还田方式在碱性土壤上对增加细菌和放线菌数量效果显著。(3)各生育时期油菜生物量以秸秆粉碎覆盖还田方式为最高,且酸性土壤高于碱性土壤。总之,秸秆粉碎与土壤混匀还田在酸性土壤上效果最好,更利于提高土壤养分含量、土壤微生物数量及油菜生物量;而在碱性土壤上则以秸秆覆盖还田方式最好。可见根据土壤酸碱度等因素因地制宜地选择适宜的秸秆还田方式是必要的。