控墒补灌下春玉米光合特性、叶片衰老研究及最适灌溉量估算

以玉米品种郑单958为材料,于2014—2015年在新疆石河子进行大田试验,设置5个控墒补灌栽培模式,研究了控墒下限对绿洲区滴灌春玉米光合特性、叶片衰老和水分利用效率的影响,并估算了本区玉米高产栽培的最佳灌溉量。试验结果表明,大喇叭口、抽雄及吐丝期土壤墒度过低或过高会显著(P0.05)降低玉米株高、叶面积指数(LAI)及干物质积累量。灌浆期土壤墒度保持在田间持水量85%的栽培模式,玉米穗位叶净光合速率(Pn)、实际光化学效率(ΦPSⅡ)、光化学淬灭系数(q P)及光合电子传递速率(rETR)可分别较墒度70%栽培模式提高71.7%、81.8%、71.6%和54.9%,但却会降低单叶的水分利用效率(WUE_L)。同时,花后同化物输入量及其对子粒的贡献率分别提高105.2%、20.3%,叶片衰老持续期延缓了8.1 d。二次曲线拟合表明,最佳灌量为539.9 mm时能取得14.9×103kg·hm~(-2)的高产,可同时兼顾产量与灌溉效益的最大化。     

不同灌水下限对灰枣树生长及水分利用效率的影响

为探究不同灌水下限对新疆典型绿洲区灰枣树生长、产量及水分利用效率的影响,于2017年在新疆建设兵团第二师38团开展了大田试验,以7 a灰枣树为试验材料,设置了滴灌方式下4个灌水下限(T1、T2、T3、T4,分别为田间持水率的40%、55%、70%、85%)。研究结果表明:随灌水下限的降低枣吊生长受到明显抑制,处理T1的枣吊长度较处理T4减少了31.84%。灌水下限对枣树产量及果实比例均有重要影响,处理T2、T3较处理T4产量提高了11.26%、4.48%,一级果果实比例提高了35.66%、21.76%。降低灌水下限有利于提高枣树水分利用效率,处理T1、T2、T3较处理T4提高了10.10%～28.28%。在沙漠绿洲区灌水下限为田间持水率的55%比较适宜灰枣的生长发育,既可抑制枣树过度营养生长、促进生殖生长、提高其水分利用效率,亦可获得较高产量。     

不同灌溉措施下春玉米干物质和养分积累分配特征及其与产量建成的相关性

通过设置田间小区试验,以郑单958为试材,研究漫灌措施下灌溉量4 800(MI1)、7 200(MI2)m~3/hm~2和滴灌条件下灌溉量4 200(DI1)、4 800(DI2)、5 400(DI3)、6 000(DI4)m~3/hm~2不同处理玉米地上部干物质和养分的累积与分配特征。结果表明,不同灌溉措施植株总干物质量大小依次为MI2DI3DI4MI2、DI2DI1,以DI3处理穗干物质积累量最高,较其他处理提高16.62%～45.51%。两种灌溉方式下,随着灌溉量的增加,显著促进了植株N和K养分吸收,滴灌处理玉米穗位K养分积累效应更明显。滴灌处理玉米子粒产量显著高于漫灌处理,其中以DI3处理最高。穗干物质量和K养分积累量与子粒产量呈极显著正相关。滴灌模式下5 400 m~3/hm~2为新疆北疆地区春玉米适宜的灌溉措施。     

Post-anthesis changes in photosynthetic traits of maize hybrids released in different years

Changes in post-anthesis physiological attributes related to genetic improvement for grain-yield were studied for six Chinese maize (Zea mays L.) hybrids widely grown in North China during the past 50 years. The characteristics assessed included light-saturated photosynthetic rate (P_sat), chlorophyll content, soluble protein content, maximal efficiency of PS2 photochemistry (F_v/F_m), PS2 efficiency (Φ_PS2), ribulose-1,5-bisphosphate carboxylase (RuBPCase) activity and phosphoenolpyruvate carboxylase (PEPCase) activity. We found that P_sat of the newer hybrids was not always higher than the older ones. However, P_sat of the 1950s hybrids was the highest among all at flowering stage, which was associated with their high PEPCase activity and soluble protein content. Post-anthesis changes in P_sat of the older hybrids can be divided into two phases. During the first phase, which was the decisive phase of grain filling, P_sat of the older hybrids declined gradually whereas the new hybrids remained relatively constant. P_sat of 1950s hybrids was not the highest among all maize hybrids any longer although their PEPCase activities were also the highest. The reduction in P_sat of the older hybrids during this phase was associated with a reduction in the chlorophyll content and the soluble protein content but was not influenced by the specific activity of RuBPCase and PEPCase. Adapting to the lowered CO₂ assimilation capacity, a down-regulation of Φ_PS2 occurred in the older hybrids to protect the photosynthetic apparatus from photo-damage by strong light, while F_v/F_m only decreased slightly during this phase, suggesting a functional PS2 apparatus in senescent flag leaves. During the second phase, the older hybrids underwent an irreversible leaf senescence that certain photosynthetic traits declined substantially with P_sat, whereas the photosynthetic components of the newer hybrids remained functional. Newer maize hybrids produced higher grain yield compared to the old ones mainly because they could remain photosynthetically active when the older hybrids aged during the grain-filling period. The decline in photosynthetic rate of older hybrids during senescence is generally attributed to the degradation of both structural and functional components of chloroplasts.