Increased Night Temperatures During Cotton's Early Reproductive Stage Affect Leaf Physiology and Flower Bud Carbohydrate Content Decreasing Flower Bud Retention

Higher than optimum temperatures during cotton's (Gossypium hirsutum L.) growing season is a common occurrence in cotton‐growing areas around the world with negative consequences on productivity. According to climate projections, night temperatures are expected to increase more than day temperatures. The objective of this study was to monitor and record the effects of higher than optimum night temperatures during cotton's early reproductive stage on physiological (photosynthesis, respiration and membrane damage) and biochemical (leaf adenosine triphosphate (ATP) levels, as well as glutathione reductase (GR) content and soluble carbohydrate concentrations of the leaf subtending the flower buds. Number, dry weight, carbohydrate concentrations and GR levels of flower buds were also measured at the end of the experiment. Growth chamber experiments were conducted using cotton cultivar ST 5288 B2RF and treatments consisted of normal day/night temperatures (32/24 °C) and high night temperatures (32/30 °C) for 7 days at squaring (approximately 4 weeks after planting). The results indicated that high night temperatures had an immediate effect on leaf respiration rates and membrane damage by significantly increasing them compared to the control and a similar pattern was observed on leaf photosynthesis and ATP levels that were markedly decreased. Leaf GR levels were also substantially increased under conditions of high night temperatures, in contrast to flower bud GR content which remained unaffected. High night temperatures had a significant effect on leaf carbohydrate concentrations resulting in significant decreases in hexose, sucrose and starch levels. Nevertheless, flower bud sucrose content was substantially increased under conditions of high night temperatures, while hexose content was decreased and starch concentrations remained unaffected. A detrimental effect of elevated night temperatures on the number of flower buds per plant and on the dry weight of flower buds was observed, and it was concluded that high night temperatures had a negative effect on cotton flower bud production due to disruptions on flower bud carbohydrate metabolism as a result of the insufficient GR response.     

Reproductive development response to high daytime temperature in field pea

Flowering plants are highly sensitive to heat stress during reproductive phase, which covers development from floral initiation to seed maturity. The objectives of this study were to diagnose high temperature effects on pollen production and morphology, production of reactive oxygen species (ROS) in pollen grains and ovules in pea cultivar “CDC Golden.” This study also investigated timing and duration of heat exposure at specific developmental stages of floral buds, open flowers and early set pods on flower and pod abortion, seed development and seed yield in “CDC Golden” and a second cultivar “CDC Sage.” The experiments were conducted in growth chambers with two temperature regimes (24/18°C and 35/18°C day/night temperature for 4–14 days) during reproductive development. Heat stress reduced the number of pollen grains per anther, induced smaller pollen grains and increased ROS production in pollen grains, but it did not affect ROS accumulation in ovules and ovule number per ovary. Heat exposure when young floral buds were visible at the first reproductive node was more detrimental to flower retention, seed set, pod development and seed yield compared to heat exposure started later when flowers at the second reproductive node were fully open.     

厚轴茶雄性不育株花药败育的生物学特性和细胞学研究

为明确厚轴茶(Camellia crassocolumnaH. T. Chang)雄性不育株花器发育形态、花药和花粉败育时期及兵细胞学特征,利用体视显微镜、石蜡切片技术、染色体制片和DAPI染色法,对厚轴茶雄性不育株和可育株开花迚程、花器形态、花药发育过程、花粉母细胞减数分裂及小孢子发育过程比较观察。结果显示,厚轴茶花属于完全花,花药其四室、呈蝶形,花药壁发育为基本型,绒毡层细胞其双核,于四分体时期形成分泌型细胞,单核花粉期开始降解,花粉母细胞经过减数分裂Ⅰ、减数分裂Ⅱ和胞质分裂后形成四面体型四分体,小孢子呈三角形,成熟花粉为二细胞型花粉。花蕾发育早期,不育株雄蕊发育正常,与可育株无明显差异。花蕾发育后期,不育株花丝弯曲,花药粘连、干瘪、褐化、坏死,不裂药。不育株减数分裂期绒毡层细胞异常增生、排列混乱,单核至双核花粉期绒毡层延迟降解。不育株花粉母细胞减数分裂过程中存在环状单价体、滞后染色体、染色体桥、染色体缺失、不均等分离、微核和多分体等异常现象。不育株小孢子胞质紊乱,单核期花粉粒相互粘附,花粉壁皱缩变形,花粉细胞质和细胞核模糊不清,成熟花粉细胞空瘪凹陷。研究结果表明,厚轴茶雄性不育花...     

南繁条件下东北春大豆杂交成功率的提高

为了加快育种进程,拓宽新品种的遗传基础,提高大豆在南繁条件下的杂交结实率,本研究选用7个东北春大豆早熟品种,在海南三亚进行光照处理和杂交技术试验,观察供试品种在长日照(18 h)处理和三亚自然短日照条件下植株形态、生长发育进程、花器官特征和花粉育性的变化,并研究光照处理、母本是否去雄和母本花蕾大小对杂交效果的影响。结果表明,海南冬季自然短日照致使大豆开花持续时间缩短,株高、花朵数量和单花重量降低,花朵及其各组成部分变小(P<0.01),花粉败育率上升(P<0.01)。以自然短日照处理植株作母本、长日照处理的材料作父本,在母本植株上选大花蕾,采用不去雄杂交,获得64.36%的杂交结实率,可基本满足杂交育种的需要。基于试验结果,提出了南繁条件下提高大豆杂交成功率的综合技术方案。     

温度和光照对富贵籽花芽分化的作用研究

为研究富贵籽成花的影响因素,探明其花芽分化与环境主要因素温度和光照的关系,以1.5~2年生盆栽富贵籽为试验材料,采用不同的温度、光周期和光照强度进行试验研究。结果表明,温度对富贵籽的花芽分化起决定性的作用,是影响富贵籽成花的主要因素,20~25℃处理下的富贵籽植株可以完成花芽分化和成花,而10℃处理的植株一直处于营养生长状态而未能花芽分化。光照对富贵籽的成花不起主导作用,在营养生长充实的条件下,无论是长日照还是短日照,只要温度合适富贵籽即可进行花芽分化,说明光周期对富贵籽的花芽分化不起作用,但合适的光照强度有利于其生长发育。     

八仙花花芽分化形态观察及成花机理研究

以八仙花“经典红”为试验材料,利用扫描电镜定期观察花芽形态发育进程,在花芽分化后期将植物进行控温促花处理,观察其开花情况,分析温度对八仙花成花的影响。结果表明,八仙花的花芽分化过程分为5个阶段,分别是营养生长期、花芽膨大期、分生组织分化期、花原基形成期以及花器官形成期；经过不同时间低温处理的八仙花均能提前开花,但未经过低温春化的植物,花品质受到一定的影响；八仙花花芽分化与温度具有显著相关性,20-25℃开始生长点膨大,15-20℃进入分生组织分化期,10℃形成花原基,5℃形成花器官并打破休眠,整个过程历时约4个月。     

川鄂连蕊茶开花生物学习性研究

首次对川鄂连蕊茶(Camellia rosthorniana Hand.-Mazz.)的开花生物学特性进行了调查,并研究了光照条件对开花的影响,旨在为品种选育和杂交育种提供依据.结果表明,川鄂连蕊茶花芽分化时间较长,经历了绿蕾期、红蕾期、透色期、松瓣期及开放期5个阶段,持续9～10个月完成.花芽主要分布于当年生小枝的枝顶和叶腋,花数/cm枝条为1.32～1.77朵,单株花期15 ～20 d,单花花期4～5d.光照条件对花芽分化影响差异显著,全光照和郁闭度0.4时花芽分化正常,郁闭度0.7时花芽数量大大减少.综上所述,川鄂连蕊茶花量大、具清香、观赏性好、适合全光照、疏林下种植或室内盆栽观赏,是良好的丰花香花型茶花育种材料.     

Exogenously Applied Plant Growth Regulators Affect Heat‐Stressed Rice Pollens

Increasing temperature due to global warming has emerged one of the gravest threats to rice production. This study examined the influence of high temperature and exogenously applied plant growth regulators on pollen fertility, anther dehiscence, pollen germination and metabolites synthesis in pollens of two rice cultivars (IR‐64 and Huanghuazhan (HHZ)). Plants were subjected to high day temperature (HDT), high night temperature (HNT) and control temperature (CT) in controlled growth chambers. Four different combinations of ascorbic acid (Vc), alpha‐tocopherol (Ve), brassinosteroids (Br), methyl jasmonates (MeJA) and triazoles (Tr) were used along with a nothing applied control. Our results depicted that high temperature severely reduced the pollen fertility, anther dehiscence, pollen retention, germination and metabolites synthesis in pollens of both rice cultivars. Nonetheless, exogenous application of various plant growth regulators assuaged the adverse effects of high temperature and Vc + Ve + MeJA + Br was found the best combination than the other treatments for every studied characteristic. The HNT posed more negative effects than the HDT. Variations were also apparent between cultivars and HHZ performed better than IR‐64 under high‐temperature stress, with higher pollen fertility, better anther dehiscence, and greater pollen retention and germination rates. The greater tolerance of HHZ to high temperature was related with the higher synthesis of metabolites in this cultivar.     

Susceptibility of Faba Bean (Vicia faba L.) to Heat Stress During Floral Development and Anthesis

Experiments were conducted over 2 years to quantify the response of faba bean (Vicia faba L.) to heat stress. Potted winter faba bean plants (cv. Wizard) were exposed to temperature treatments (18/10; 22/14; 26/18; 30/22; 34/26 °C day/night) for 5 days during floral development and anthesis. Developmental stages of all flowers were scored prior to stress, plants were grown in exclusion from insect pollinators to prevent pollen movement between flowers, and yield was harvested at an individual pod scale, enabling effects of heat stress to be investigated at a high resolution. Susceptibility to stress differed between floral stages; flowers were most affected during initial green‐bud stages. Yield and pollen germination of flowers present before stress showed threshold relationships to stress, with lethal temperatures (t₅₀) ?28 °C and ~32 °C, while whole plant yield showed a linear negative relationship to stress with high plasticity in yield allocation, such that yield lost at lower nodes was partially compensated at higher nodal positions. Faba bean has many beneficial attributes for sustainable modern cropping systems but these results suggest that yield will be limited by projected climate change, necessitating the development of heat tolerant cultivars, or improved resilience by other mechanisms such as earlier flowering times.     

雄性不育野生茶树开花生物学特性

为观察野生茶树雄性不育株开花生物学特性,探讨野生茶树雄性不育表型特征。以野生茶树雄性不育株及可育株为试材,田间观察了野生茶树的开花物候期、单花发育进程和花器形态特征,并采用离体萌发法、染色法测定其花粉活力和柱头可授性。结果表明：野生茶树雄性不育株开花物候期为9月上旬—10月上旬,全花期持续约29~33天,花期与对照材料相近。雄性不育花从花芽分化至花瓣凋谢平均历时约107天,比对照长14天。雄性不育花器结构具有典型的雄不育特征,表现为花冠开展度小,花丝弯曲畸形,花药彼此粘连,皱缩干瘪,不裂药,花药内无花粉或有微量败育花粉。雄性不育花雌性器官发育正常,柱头从开花前1天至开花后4天具有可授性,最佳授粉时间为开花后1天。所调查的野生茶树雄性不育类型属于花药败育型和花粉败育型。     

Microsporogenesis and flower development in Eucalyptus urophylla × E. tereticornis

We compared microsporogenesis and flower development in Eucalyptus urophylla × E. tereticornis. In this study, although microsporogenesis and cytokinesis occurred simultaneously during meiosis of pollen mother cells, we observed a strong asynchronism in different anthers from a flower bud. The developmental period of microsporogenesis in anthers originated from the long thrum before the short thrum. Flower development was also asynchronous at different locations on a branch. The flower buds grew on the lower side of the branch and showed greater increases in diameter. In addition, we observed a relationship between microsporogenesis development and flower bud diameter growth. Generally, when the pachytene stage was first observed in a small single flower bud growing on top of a flowering branch, the remaining microsporogenesis stages (from diplotene to tetrad) in the whole branch occurred over the next 5–9 days. Thus, the start of microsporogenesis in E. urophylla × E. tereticornis could be determined, which may be applicable to future breeding studies.     

Genetic Variation for Heat Tolerance During the Reproductive Phase in Brassica rapa

We investigated heat tolerance at the reproductive stage in six spring‐type B. rapa accessions and one B. juncea accession as a control. Plants were subjected to two temperature treatments for seven days in controlled environmental rooms, beginning one day before the first open flower on the main stem inflorescence. The high‐temperature treatment ranged from 25 °C to 35 °C during 16 h light and 25 °C during 8 h dark. The control temperature treatment was set at 23 °C during 16 h light and 15 °C during 8 h dark. Soil moisture was maintained at close to field capacity to avoid drought stress. Main stem buds that emerged during the treatment period were tagged, and pod and seed production was recorded at each reproductive node. Leaf temperature depression and leaf conductance increased in the high‐temperature treatment which indicated that plants were not drought stressed. A leafy vegetable type of B. rapa from Indonesia was the most tolerant to high temperature, as defined by its ability to set seed equally well in the control and high‐temperature treatments, followed by an oilseed type from Pakistan. Pollen viability remained above 87 % in all accessions and treatments. We conclude that bud number and length, and pod number produced under high temperatures, might provide a useful preliminary screen for high‐temperature tolerance and that B. rapa may be a valuable source of heat tolerance in canola (B. napus).     

棉花GhMADS12基因的克隆及其表达载体的构建

MADS-box基因是真核生物中一类重要的转录调控因子,调节着植物根、茎、叶到花的发育和果实的成熟。本研究以中棉所36花发育期均一化全长cDNA文库为基础,分离出一个棉花的MADS-box基因全长cDNA命名为GhMADS12。同时利用pBI121双元载体成功构建了GhMADS12基因的植物过表达载体,并利用基因枪轰击法瞬时表达载体,验证了载体的可靠性,为下一步转基因验证基因的功能奠定了基础。     

Cotton yield and fiber quality affected by row spacing and shading at different growth stages

Carbohydrate production and reproductive structure development in cotton (Gossypium hirsutum) depends on light availability, a determinant of cotton yield. Light availability is decreased by cloud cover or self-shading when cotton plants are grown in dense populations. The objective of this study was to evaluate the effects of shading during cotton growth and its interactions with plant row spacings on yield and fiber quality. Three independent experiments were conducted as follows: in Paranapanema (23°39′S; 48°58′W), cotton was planted in November in row spacings of 0.45, 0.75 and 0.96 m; in Primavera do Leste (15°33′S; 54°11′W), planting was in January with at row spacings of 0.45 and 0.76 m; and in Chapadão do Céu (18°38′S; 52°40′W), cotton was planted in February in rows spaced at 0.45 and 0.90 m. Plants were exposed to shading during the phenological stages B1 (floral bud), F1 (early flowering), PF (peak flowering) and 3OB (fruit maturity). In addition, there was one treatment without shade. There were no interactions of crop spacing with shading. Increasing plant population and shading both decreased net photosynthetic rate. The number of bolls m⁻² increased with higher plant populations only when planting was delayed, and were not affected by shading. When cotton was planted in November and January, higher yields were obtained at 0.75/0.76 m, but when planting was delayed to February, 0.45 m resulted in higher yields with no effect on fiber quality. Shading for eight or ten days decreases boll weight and yields, but do not affect fiber quality. Cotton yield is the most decreased when shading occurs during flowering. These results may be used to build management strategies to minimize shading effects by adjusting cotton sowing time and plant density, by selecting cultivars with increased shade tolerance and by choosing an adequate irrigation period to improve yield.     

Morpho-physiological and phenological attributes of reproductive biology of tea (<Emphasis Type="Italic">Camellia sinensis</Emphasis> (L.) O. Kuntze) in Sri Lanka

A comprehensive knowledge on reproductive traits is a prerequisite in utilizing the existing tea germplasm effectively for crop improvement to develop superior planting material for grower acceptance and market profitability. The Sri Lankan tea germplasm was characterized based on reproductive traits viz. floral morphology, pollen biology, stigma receptivity and phenology of flowering and fruit set. The variability in floral morphology, especially the style morphological features, formed phenotypic clines rather than distinct groups. Studies on pollen biology and stigma receptivity revealed significant variability and asynchrony that could result unequal reproductive success among the genotypes. Four distinct patterns were predictable among the genotypes based on flower and fruit abundance and the time of flowering and fruit set. Three well marked flowering periods occurred in February to April, July and in November. Nonetheless, major flowering period coincided February and March in all the genotypes allowing free crossing between the different genotypes. Profuse mature fruit crop was obtained in February to May. Approximately 26% success was achieved in tea controlled hybridization programmes. Fruits carry two seeds on average and became mature in 8–9 months after pollination. Zygotic development in tea takes more than 1 month after pollination and early embryonic development continued for 4 months after pollination. The indexing of the morpho-physiological diversity and the phenological calendars of flowering and fruit set made available in the study are of significant importance in effective utilization of the tea germplasm for crop improvement.     

The effects of high-temperature stress on the germination of pollen grains of upland cotton during square development

The reproductive stage of flowering plants is sensitive to high-temperature stresses. High temperature is a major factor influencing pollen grain viability in upland cotton (Gossypium hirsutum). The objective of this study was to identify the relationship between cotton pollen germination percentage and temperature by assaying the pollen germination of four upland cotton cultivars in vitro at different temperatures during the blooming period. The results showed that in vitro pollen germination percentage was related to the culture temperature of pollen germination and the temperature of the square development process. High temperature affected pollen development and germination, and high-temperature tolerance differed among the cotton cultivars. The pollen germination percentage decreased rapidly with changes in the culture temperature from 30 to 39 °C. A culture temperature of 35 °C might be a critical temperature for the pollen viability transition and could be used to screen cotton cultivars that have pollen grains with high-temperature resistance. Before the high-temperature stage, cultivars with rates of decrease in the percentage of pollen germination of less than 41 % at 35 °C relative to the rates at 30 °C might be considered as high-temperature tolerance cultivars, and cultivars with rates of decrease in the percentage of pollen germination greater than 41 % might be considered as susceptible cultivars. The high-temperature stress for pollen grain germination in vitro was greater than 30 °C, and the high-temperature stress for square development might be greater than 33 °C. Boll retention was significant; it was positively correlated with the pollen germination percentage and negatively correlated with temperature during the high-temperature stage. This study provided a method for rapidly screening cultivars (lines) with high-temperature tolerance pollen in upland cotton breeding.     

基于不同肥源的棉花减氮施肥效果比较研究

棉花生产中施氮量高、氮肥利用效率低的问题较为突出。以不施氮肥（CK）和当地习惯施肥（CF,施N 270kg/hm ²,普通复合肥）为对照,在田间条件下研究了生物有机复合肥（T1）、控释掺混肥（T2）、有机无机复混肥（T3）3种肥源减氮（N）20%对麦后移栽棉花生长、产量及氮素利用效率的影响。结果表明：T2处理整个生育期棉花最新完全展开叶净光合速率（P_n）均高于其他处理,且到花铃期显著高于CF。蕾期T1处理叶、茎、蕾干物质重显著高于其他处理,花铃期T2处理茎干物质重显著高于CK、T1和T3处理。花铃期棉株氮吸收量T2处理最高,分别比CF、T1、T3高27.0%、19.7%、36.5%,其中生殖器官（蕾、铃）氮吸收量亦是T2最高,分别比CF、T1、T3高46.1%、13.6%、35.3%。T2处理较CF显著增产3.4%,其氮肥表观利用率、氮肥偏生产力和氮肥农学利用率分别为28.6%、13.6kg/kg和5.6kg/kg,显著高于CF的19.0%、10.5kg/kg和4.1kg/kg,同时T2处理的产投比最大（3.7）,净收入最大（13 925.5元/hm ²）。     

低温处理对蝴蝶兰生长发育及叶绿素荧光参数的影响

为研究温度对蝴蝶兰营养生长和生殖生长的影响,以3个蝴蝶兰品种为试验材料,采用叶绿素荧光测量方法和统计学方法,对不同温度处理下蝴蝶兰叶片生长情况和花梗抽梗情况进行研究。研究表明：（1）蝴蝶兰花芽分化需要经历春化作用,26/18℃（日/夜）处理处理可使3个品种在1个月内启动花芽分化,而29/21℃（日/夜）处理的对照组均无抽梗。（2）同时,生殖生长抑制营养生长,3个品种的成熟叶片平均长度均小于对照组。（3）低温处理导致Fv/Fm降低,Fo增高,叶绿素荧光参数能敏感地反映低温引起植株光合机构变化的情况,可间接地作为快速鉴定蝴蝶兰花芽分化的指标。     

1‐Methylcyclopropene (1‐MCP)‐Induced Alteration in Leaf Photosynthetic Rate,Chlorophyll Fluorescence,Respiration and Membrane Damage in Rice (Oryza sativa L.) Under High Night Temperature

High night temperature (HNT) can induce ethylene‐triggered reactive oxygen species production, which can cause premature leaf senescence and membrane damage, thereby affecting production, consumption and transfer of photosyn‐thates, and yield. The 1‐methylcyclopropene (1‐MCP) can competitively bind with ethylene receptors and decrease ethylene effects. The objective was to determine the effects of HNT and 1‐MCP on leaf photosynthetic rate (P_N), chlorophyll fluorescence, total chlorophyll (TC), respiration, membrane damage, pollen germination, spikelet fertility (SF) and yield of rice hybrid ‘XL723’. Plants were grown under ambient night temperature (ANT) (25 °C) or HNT (30 °C) with or without 1‐MCP treatment. Application of 1‐MCP was at the boot stage. The decrease in yield (11 %) under HNT was associated with decreased P_N (4 %), stomatal conductance (8 %), quantum yield (11 %) TC (23 %) and SF (5 %) and increased respiration (74 %), F_o/F_m (increase in thylakoid membrane damage; 11 %) and membrane damage (leaf electrolytic leakage; 57 %). The 1‐MCP‐treated plants grown under HNT showed increased yield (17 %), which was associated with increased P_N (10 %), stomatal conductance (30 %), quantum yield (9 %), TC (37 %) and SF (11 %) and decreased respiration (39 %), F_o/F_m (5 %) and membrane damage (18 %). Plants grown under HNT showed increased grain chalkiness (154 %) compared with plants grown under ANT.     

Shortening the generation cycle in faba bean (Vicia faba) by application of cytokinin and cold stress to assist speed breeding

The aim of this study was to reduce the length of the breeding cycle for faba bean by accelerating seed setting. We examined the mode and time of exogenous 6-benzylaminopurine (BAP) (cytokinin) application, and cold treatments and their combinations in two faba bean genotypes. Acropetal node number of pod and seed set and pollen viability were recorded during the experiments. Application of BAP improved pollen germination. The application of 10^–5 M BAP 4 days after flowering increased seed set at the lower nodes. Cold treatment (8/4°C day/night for 2 days) after the onset of flowering induced the formation of more pods and faster pod set compared to the non-cold treatment. The time to first seed was significantly reduced, and pollen viability was increased in plants exposed to cold treatment. Increased pollen viability also showed a significant positive correlation with seed setting. The combinations of 10^–5 BAP and cold treatment together had similar and independent effects. These results will accelerate plant breeding in faba bean by providing additional tools for reducing generation time.