Water Stress and Potassium Fertilization in Field Grown Maize (Zea mays L.): Effects on Leaf Water Relations and Leaf Rolling

Three cultivars of maize ( Zea mays L.) were grown in the experimental field at Hiroshima University, Japan under two levels of K fertilization with a non-irrigated water stress treatment and an irrigated control during June to August 1990. Leaf water potential, osmotic potential and stomatal conductance were measured 21 d after withholding water. Diurnal changes in degree of leaf rolling were measured on the 22nd day after withholding water. Leaf water potential and osmotic potential at full turgor were lower in the non-irrigated plants than irrigated and they were lower in the high K plants than the low K plants. Lowering of osmotic potential (osmotic adjustment) helped to maintain turgor under low water potential conditions. Turgor potential was increased by the higher K fertilization. Higher turgor potential may contribute to the higher stomatal conductance observed in non-irrigated high K plants. The degree of leaf rolling increased towards noon, and it was lower in high K plants than in low K plants. High K plants recovered from leaf rolling faster than the low K plants during the afternoon. High K. plants could maintain higher turgor potential throughout the day than the low K plants. Degree of leaf rolling was the lowest in the cultivar K-8388 which maintained the highest turgor potential via osmotic adjustment and it recovered from leaf rolling faster than the other two cultivars. Higher levels of K fertilization may be beneficial for maize plants to tolerate to water stress conditions.     

Yield and Agronomic Characters of Tropical Maize (Zea mays L.) Cultivars under Different Irrigation Regimes

Drought spells are unpredictable under tropical conditions and can occur at every growth stage of the maize plants. Little is known about the reactions of tropical maize cultivars to water shortage. A set of Thai cultivars was examined in the field during the dry season. Three stress situations were imposed: prolonged stress throughout the growing season, pre- and post-anthesis stress. Pre-anthesis water stress delayed flowering and especially the data of silking. Thus, the anthesis-silking interval was wider. Prolonged water stress decreased grain yield mainly due to a low number of kernels and/or thousand kernel weight (TKW). Post-anthesis stress mainly reduced TKW grain set per ear. Relief from pre-anthesis stress increased grain yield by a grater number of kernels and higher TKW as compared to prolonged stress. Genotypic differences were high for the anthesis-silking interval following pre-anthesis stress. Low yielding, early but generally drought-stable cultivars existed as well as cultivars which were generally high yielding even under water stress because of a good residual yield. Some cultivars were resistant to pre-anthesis stress but not to post-anthesis stress and vice versa. It can be concluded that ample genotypic variability exists for adaptation to varying situations of pre-and post-anthesis stress within tropical maize cultivars.     

Effect of Salt Stress on the Salicylic Acid Synthesis in Young Maize (Zea mays L.) Plants

The effect of salt stress on salicylic acid (SA) synthesis was investigated parallel with the induction of antioxidant enzymes in young maize plants. Two-week-old maize plants grown in hydroponic solution were treated with 50 or 100 m m NaCl for 7 days. Antioxidant enzyme activities, and the SA and o -hydroxy-cinnamic acid (oHCA) levels were measured on the 3rd and 7th day of treatment and after 4 days of recovery. Ascorbate peroxidase activity increased in the leaves, but changes in guaiacol peroxidase activity only could be detected in the roots after 7 days. Glutathione reductase activity increased both in the leaves and in the roots after the 3rd day of 100 m m NaCl treatment. Free SA only increased during recovery in the leaves and roots. In the leaves of plants treated with 100 m m NaCl, a slight increase was observed in the free oHCA level, which rose dramatically after recovery, while in the roots an increase could only be seen after recovery. These results suggest that oHCA may serve not only as a precursor of SA but may also have an antioxidant role during salt stress and recovery.     

Genotypic Variation for Cold Tolerance among Twelve Maize (Zea mays L.) Populations

The objectives of this study were (1) to ascertain the genetic differences for cold-tolerance traits in a series of diallel crosses among 12 maize populations grown in field experiments, and (2) to compare, in controlled environment rooms, the modification of various metabolic parameters of two sets of four F1 variety crosses which, according to the field experiments, differed largely in seedling early vigour (cold-tolerant [Ct] vs cold-sensitive [Cs] Fl sets). Under field conditions, cold-tolerance adaptability, as monitored by shoot dry matter accumulation, appeared genetically controlled; moreover, considerable differences existed among genotypes. Field data suggested that shoot dry weight was a good indicator of plant adaptability to periods of unfavorable cool conditions. The growth-chamber experiments showed that shoot dry weights of the two sets of hybrids (Ct vs Cs), were more uniform at the highest temperature regimes than under suboptimal temperatures. Moreover, the laboratory study indicated that the interval of time of attain a specific stage of development provided a meaningful and useful criterion for differentiating the capacity of maize plants to grow at low temperatures. Although a clear association between a particular metabolite and the capacity of plants to grow at low temperatures was not observed, it was of interest to note that the total N concentration in the shoot was significantly higher in the Ct plants compared to the Cs ones.     

渍涝胁迫对玉米生理生化的影响研究进展

渍涝胁迫是玉米生产中重要的非生物逆境之一,对玉米的生长发育造成危害,严重制约了玉米产量的提升。因此回顾了人们针对渍涝胁迫对玉米生理生化的影响及其适应机制的研究,介绍了人们从栽培耕作和遗传育种两个角度提高玉米抗渍涝能力的研究现状,并展望了未来玉米抗渍涝胁迫的重点研究方向。     

Water Stress and N Fertilization Effects on Yield and Smut Disease Incidence in Corn (Zea mays L.)

A 2-year field experiment was conducted in sandy clay loam soil to quantify the single and combined effects of N fertilization and water stress (WS) treatments on yield and smut incidence in corn. The plants were supplied with two different N rates (225 and 300 kg ha⁻¹) and subjected to 2 weeks' water stress, imposed at vegetative (Vg), tasselling (Ta), silking (Si) and grain-filling (Gf) growth stages. In addition, a control treatment (Cr) was also included to allow the plants to grow under unstressed conditions. The plants were artificially infected two times with Ustilago maydis spores and smut severity was recorded. At harvest, grain yield (GY), total biomass (Tbm) and harvest index (HI) were determined in smut-free (0) and smutted plants (S). Results have shown that GY₀ and GY_s were markedly reduced when the plants were subjected to WS. The depressing effects of WS were, comparatively, high at Gf. intermediate at Ta and Si. and low at Vg growth stages. Smut index (SI) data revealed that severity was higher on plants stressed at Gf than those exposed to WS at Vg, Ta or Si stages. Considerable variations were detected on Tbm and HI of smut-free and smutted plants, indicating the detrimental effect of plant water deficit at Gf stage. The combined effect of WS and N on Tbm_s showed mixed results, ranging from positive response for stressed plants at Si and Gf to little response at Cr, Vg or Ta stages at higher N rate. Although the effect of WS exposure on RYL data was dominant at Gf, the rate of yield depression was relatively higher at Ta and Si than the other growth stages, because of water deficit effects. The results proved that N fertilization did not conclusively alleviate the depressing effect of WS on grain yield losses.     

The early stress response of maize (Zea mays L.) to chloride salinity

Chloride is a micronutrient required for photosynthesis but when applied in the concentration of a macronutrient, it may also promote growth by regulating turgor. However, if chloride accumulates excessively, it can induce toxicity. The aim of this study was to identify physiological dysfunctions in maize (Zea mays L.) that arise in response to excessive chloride ion accumulation. For this, a novel water sensor was employed for the first time allowing the in vivo measurement of water content in the plant by using two near IR‐wavelengths with different absorption of water. This enabled to analyse whether water imbalances occurred. Chloride was given together with calcium as companying counter cation. Results show that most of the tested maize genotypes were able to maintain growth, photosynthesis and normal water content when stressed with concentrations as high as 757.1 mg chloride/kg soil dry matter. Leaf blades accumulated only 8.5 mg chloride/g dry matter, with the most genotypes not even showing salt stress necrosis at the leaves. A comparison between more tolerant and more sensitive genotypes revealed that restriction of chloride root‐to‐shoot translocation is a trait of chloride tolerance.     

玉米花期性状的全基因组关联分析

花期性状是玉米的重要性状,与熟期、散粉结实率和产量关系密切,对玉米品种选育至关重要。为探究玉米花期性状的遗传基础,本研究以248份遗传多样性丰富的玉米自交系作为关联群体,通过2017年和2018年在河北保定和辛集的田间试验调查抽雄期、散粉期、吐丝期和散粉吐丝间隔期4个花期相关性状,利用分布于全基因组的83057个SNP标记进行关联分析。结果表明,4个花期相关性状的基因型、年份、地点、基因型与地点的互作、基因型与年份的互作均达到极显著水平;抽雄期、散粉期、吐丝期的遗传率分别为71.77%、71.27%、73.93%,并且两两性状间呈极显著正相关,散粉吐丝间隔期遗传率为62.50%,仅与吐丝期呈极显著正相关;4个花期性状共检测到18个SNPs-性状关联(共涉及16个SNP位点),单个位点的表型贡献率范围为5.46%~28.36%,仅1个位点在不同性状中检测到;筛选到81个候选基因,其中36个在GO分析中具有功能注释。潜在候选基因GRMZM5G877647编码early flowering 4蛋白,参与光周期的调节;GRMZM2G173630编码类赤霉素受体蛋白参与植物激素信号转导;GRMZM2G001139、GRMZM2G375707编码与花器官建成的MADS转录因子。这些潜在候选基因为解析玉米花期性状遗传基础和分子辅助选择育种提供参考。     

苗期水分胁迫对玉米根系生长杂种优势的影响

以玉米杂交种高油115及其亲本(母本220、父本1145) 为材料, 研究了玉米苗期根系生长的杂种优势及水分胁迫的影响。试验设水分充足、轻度干旱和严重干旱3个处理, 田间持水量分别为75%、55%和35%。结果表明, 在水分充足条件下, 根长(RL)、根表面积(SA)和根干重(RDW)均表现出不同程度的中亲优势和超亲优势, 轻度干旱显著降低了各指标的杂种优势, 而严重干旱则完全抑制了根系生长的杂种优势。根系各性状中, RL的杂种优势最强。在水分充足条件下, 与中等根(根直径0.25~0.45 mm)和粗根(根直径>0.45 mm)相比, 细根(根直径0.05~0.20 mm)的RL、SA及其占总根系比例的杂种优势最高。轻度干旱胁迫虽然降低了根系的杂种优势, 但RL、SA仍表现出显著的超亲优势和中亲优势(粗根的超亲优势除外)。此外, 只有细根RL和SA占总根系的比例在轻度干旱胁迫下具有显著的中亲优势, 说明杂交种可以通过生成较亲本更高比例的细根来抵抗轻度干旱胁迫。     

The Influence of Plant Water Stress on Net Photosynthesis and Leaf Area of Two Maize (Zea mays L.) Cultivars

The effect of plant water stress on net photosynthesis and leaf growth were investigated in order to determine to what extent leaf water potential during vegetative growth and silking affects maize development.
Two commercial maize hybrids grown in pots in a glasshouse were subjected to leaf water potentials of -1300 and -1700 kPa during the eighth leaf stage and during silking to -1700 and -2300 kPa to previously unstressed, moderately and severely stressed plants. The effect of stress on inhibiting CO₂ uptake rates and leaf areas, as well as the recovery after alleviating stress, were compared to that of unstressed plants.
No substantial differences in CO₂ uptake rates were found between medium and long seasoned cultivars. The CO₂ uptake rates per unit leaf area decreased to negative values under both moderate and severe stress conditions during both growth stages. During silking, the recovery of CO₂ uptake rate was much lower than during the eight leaf stage. Leaf area decreased proportionally with increased stress but did not recover after alleviating stress on plants stressed during both the eighth leaf and silking stages.     

四川地方玉米种质的SSR聚类分析

利用SSR分子标记方法研究28个玉米自交系的遗传变异。分析四川地方玉米种质的遗传基础,并进行SSR聚类分析,探讨四川地方玉米种质与国内主要杂种优势群的关系。结果表明：大部分四川地方玉米种质均可被划分到常见的几大杂种优势群中去,少数地方玉米自交系可形成单独的类群,四川地方玉米种质具有广泛的遗传基础;SSRs能较真     

若干玉米胚乳突变体基因效应的研究

对５个玉米单隐性胚乳突变体、３个双隐性胚乳突变体的可溶性糖（还原糖、蔗糖）、水溶性多糖、淀粉、粗蛋白、赖氨酸含量测定，并对突变体种子结构扫描电镜观察。分析了玉米胚乳突主体的基因效应及其互作效应。     

普通玉米3个籽粒品质性状的配合力分析

以10个普通玉米自交系及其90个杂交组合在北京和山西2个地点的试验数据,分析了蛋白质、淀粉和油分含量的配合力效应。结果表明：(1) 各性状的一般配合力(GCA和特殊配合力(SCA) 均方极显著,且GCA均方大于SCA均方,说明它们在遗传上主要受加性基因效应的影响。(2) 杂交种的3个品质性状与亲本GCA平均值和SCA极显著正相关,但与亲本GCA均值间的相关性相对较强,其相关系数(r)分别为0.708**(蛋白质)、0.756**(淀粉)和0.772**(油分),表明提高亲本GCA对改良杂交种品质具有更大的作用。(3) 自交系BT1和E28的蛋白质含量GCA较高,掖478、昌7-2、掖107和48-2的淀粉含量GCA较高,E28、黄C和P138的油分含量GCA较高。     

夏玉米光合特性对氮素用量的反应

随氮素用量增加,植株下位叶、穗位叶和上位叶的光合速率（P_n）、叶绿素含量（Chl）、可溶蛋白含量（Pro）、Hill反应活性、Ca²⁺-ATPase活性、Mg²⁺-ATPase活性和PEPCase活性均不断增大。植株不同叶位Pn和Pro随生长进程均不断下降;不同叶位Chl的变化动态表现为下位叶在各测定时期之间差异较小、穗位叶和上位叶为单峰曲线。Hill反应活力、Ca²⁺-ATPase活性和Mg²⁺-ATPase活性的变化规律不同,随生长进程表现不断下降、单峰曲线和双峰曲线等不同形式。各叶位PEPCase活性均表现单峰曲线型变化。随氮素用量增加,叶源量、生物产量和籽粒产量不断增加。适量施氮具有全面改善玉米光合效率和内在生理、生化过程的作用。Ca²⁺-ATPase活性是影响光反应活力的重要因素;在叶片生长前中期,P_n受到PEPCase的影响较小,主要受到光反应活力和暗反应效率的调控。可采用叶源量作为玉米单株生产力的参考诊断指标。     

Effect of Low Night Temperatures on Photosynthetic Activity of the Maize Seedlings (Zea mays L.)

Night chilling (5 °C) subsequently lowered photosynthetic intensity in the leaves of maize seedlings at 20 °C through an increase in leaf diffusive resistance brought on by lower tissue water content in morning hours. A more significant increase in leaf diffusion resistance was observed when soil temperature was lowered than in the case of lower air temperature.
The unfavorable effect of soil and air cooling temperature on photosynthesis was limited by air saturated with water vapour. However, as a result of lowering the night temperature from 5 °C to 1 °C, the efficiency of the protective influence of higher atmospheric humidity was decreased. This demonstrates that the participation of factors unrelated to plant water status in inhibiting photosynthesis increases with lower night temperatures.
An additional reason for inhibited photosynthesis following cool nights was a decrease in chlorophyll accumulation, below 50 μg per 1 cm² of leaf area.     

利用cDNA—AFLP技术研究玉米基因的差异表达

利用cDNA-AFLP技术，对玉米强优势组合和弱优势组合及其双亲自交系在苗期和雄穗生长锥伸长期的基因表达进行了分析。结果表明，玉米强优势组合和弱优势组合的基因表达有明显差异，基因表达有多种类型，表现出质和量的差异，不仅有增强，也有双亲沉默，弱优势组合双亲沉默的数量在苗期和雄穗生长锥伸长期均高于强优势组合，杂     

影响玉米花药培养效率的因素研究

对影响玉米花粉胚诱导的因素进行了研究。结果表明 :花药接种前对雄穗进行 5℃低温预处理 15～ 2 1d效果较好 ;接种后高温 (33℃ )连续处理花药 ,胚出现早、质量好且效率高 ;活性炭 (0 5 g/L)加入培养基中能显著地提高胚诱导效率。此外 ,还对基因型间差异进行了比较分析     

水稻、大豆、玉米光合速率的日变化及其对光强响应的滞后效应

用LI-6400光合测定系统对水稻、大豆和玉米3种作物在不同生育时期叶片光合速率的日变化规律进行了研究。结果表明:在各个生育时期,C3作物(水稻、大豆)叶片的光合作用均存在午休现象。而午休现象的产生是气孔因素与非气孔因素共同作用的结果。其中“气孔因素”是高温加剧蒸腾作用,气孔对蒸腾作用的反馈抑制造成的。C3作物(水稻、大豆)叶片的光合速率对光强的响应在上午和下午存在明显差异,上午利用光能的能力明显大于下午。这主要表现在上午的表观初始量子效率比下午大。光合产物对光合作用的反馈抑制会造成这种量子效率的差异性。无论是气孔限制还是光合产物反馈抑制都可能是导致光合速率对光强响应产生“滞后效应”的主要原因。C4作物(玉米)的午休现象不明显,光合速率对光强的响应在上午和下午的差异也不明显,不存在明显的“滞后效应”,这可能与C4作物(玉米)自身的生理特性适应高温的能力有关。     

玉米籽粒发育性状的遗传及与产量性状关系的研究

在含有 BA(6-苄基腺嘌呤)2.5毫克/升、NAA(萘乙酸)0.1毫克/升的 MS 培养基上诱导苎麻(Boehmeria niveaL.)试管苗未离体叶面生芽。比较了不同激素的效果,在诱导芽形成中 BA 优于 ZT(玉米素)和 KT(激动素)。在叶脉处,特别是在中脉维管束的薄壁细胞容易分裂和脱分化,且具有较强的分化能力。芽在叶面上发生有一定的规律,并对叶面     

低磷胁迫对磷不同利用效率玉米叶绿素荧光参数的影响

盆栽试验在高磷（+P）和低磷(－P)条件下,于四叶期测定了磷高效利用型玉米KH5和磷低效利用型玉米齐201的老叶（第2叶）和新展开叶的（第4叶）叶绿素荧光诱导动力学参数。结果表明,低磷处理使玉米叶片PSⅡ关闭程度增加、光能转换和电子传递效率降低,过剩激发能增加。基因型间比较,磷高效利用型玉米的光能转换和电子传递效率