菊花花芽分化初步研究

菊花花芽分化有花序分化和小花分化两个过程,可分9个时期统计。‘黄金球’8月31日开始花芽分化,9月31日完成分化;‘银蜂铃’9月6日开始花芽分化,10月6日完成,两品种完成花芽分化均需30天。‘黄金球’花芽分化时,日照12.7h,‘银蜂铃’12.6h,两品种花芽分化的临界日照均在12～13h。‘黄金球’在平均气温25.5℃时开始花芽分化,‘银蜂铃’是22℃。高温为制约其花芽分化的主要因素之一,但品种间的反应有所不同,当平均气温在20℃左右时分化速度最快。     

不同光周期和褪黑激素对绒山羊生产性能影响

本研究在山羊非长绒季节（２～６月），在人工控制环境条件下，通过改变光周期和褪黑激素处理，探讨对绒山羊生产性能的影响。研究结果表明：每日８小时光照，不论褪黑激素处理与否，山羊都能长绒；每日１６小时光照，经褪黑激素处理，可诱使山羊长绒。随产绒量增加，绒纤维长度和细度显著变化。光周期和褪黑激素是影响山羊绒生长的主要因素。     

Effect of semen collection frequency on seasonal variation in sexual behaviour,testosterone, testicular size and semen characteristics of tropical hair rams (<Emphasis Type="Italic">Ovis aries</Emphasis>)

The purpose of this study was to examine the effect of day length on seminal characteristics, testicular size, sexual behaviour and testosterone (T4) concentration in Pelibuey rams subjected to different semen collection frequencies. Eighteen intact males were assigned randomly to one of two semen collection frequencies: in the high rate (HR) treatment, two ejaculations per week were obtained from each ram; one ejaculation every two weeks was collected under the low rate (LR) treatment. All animals were housed individually in contiguous 5 m × 5 m wire mesh pens and evaluated over a 12-month period. At the beginning of the experiment rams were 20 months old and 40–50 kg in weight. All rams ejaculated and produced semen throughout the year. Semen volume, sperm per ejaculation, testicular circumference and testicular volume were significantly (p < 0.05) greater during short days in all rams, regardless of the semen collection frequency, with the exception of sperm concentration, for which no variation was found in HR individuals, and reaction time and T₄ levels, for which no variation was found in LR males. Rams subjected to HR collection were more affected by the short-day photoperiod than rams collected twice per week, exhibiting greater reduction (p < 0.05) in time to achieve their first ejaculation and in sperm per ejaculation, as well as greater increases (p < 0.05) in T₄ concentration than LR rams (14.65 ± 1.22 vs 23.53 ± 5.34 s, (3.37 ± 0.17) × 10⁹ vs (3.52 ± 0.20) × 10⁹ sperm and 8.68 ± 0.44 vs 6.85 ± 0.74 ng/ml, respectively). It was concluded that: (a) the magnitude of the seasonal effects was not sufficient to prevent the rams being used for breeding throughout the year, and (b) seasonal variation within variables was affected differently between semen collection frequencies.     

In vitro evidence that leptin suppresses melatonin secretion during long days and stimulates its secretion during short days in seasonal breeding ewes

Recent observations in seasonal-breeding mammals indicate that the hypothalamus is programmed to become leptin resistant during long days (LD) and leptin sensitive during short days (SD). These observations support the possibility that photoperiod mediates at least part of its effects on melatonin secretion through changes in leptin sensitivity. Herein we examined the interaction of season and recombinant ovine leptin (oleptin) on melatonin secretion by pineal explants in short-term culture. Glands were collected after sunset from eight ewes during LD (March, April, May, June) and from an additional eight ewes during SD (September, October, November, December). Glands were transected saggitally and coronally into quarters, with each equilibrated in 2.5ml of DMEM for 120min, followed by a 3h incubation in medium containing either 0 or 50ng/ml of oleptin. Treatment with oleptin reduced (P<0.001) melatonin secretion compared to controls during LD by approximately 22% at 2, 2.5 and 3h of culture. However, in cultures from glands collected during SD, oleptin stimulated (P<0.078) melatonin secretion approximately 50% compared to control. These effects were consistent throughout each respective season. We conclude that the secretion of melatonin from the ovine pineal gland is negatively responsive to leptin during LD, whereas leptin may stimulate melatonin secretion during SD.     

光周期对梨小食心虫生长发育和生殖的影响

探讨光周期变化对梨小食心虫生长发育和生殖的影响,为科学预测梨小食心虫种群动态的季节变化提供理论依据。在温度(26±0.5)℃,RH(70±10)%人工气候箱中,研究15L∶9D、14L∶10D、13L∶11D、12L∶12D和11L∶13D 5个光周期对梨小食心虫生长发育和生殖的影响。不同光周期条件下梨小食心虫幼虫发育历期、成虫寿命和产卵量明显不同(P0.05),12L∶12D条件下幼虫发育历期最短、成虫寿命最长,产卵量最高;13L∶11D条件下幼虫发育历期最长;11L∶13D条件下成虫寿命最短,产卵量最低。但成虫产卵前期无显著差异(P0.05)。光周期变化对梨小食心虫的生长发育和生殖具有显著的影响。     

21个切花菊品种的光周期与花期调控研究

[目的]研究切花菊的光周期和花期调控。[方法]比较了广州地区常见的21个切花菊品种（11个小菊品种和10个大菊品种）光周期反应。[结果]根据短日照至开花的周数（即光周期敏感性）,切花小菊品种可分为6~10周菊;大菊品种可分为9~12周菊类。为达到切花菊的标准株高,推算不同品种秋冬季长日照灯控处理的天数在14~66 d不等。[结论]为广州地区切花菊的花期调控和延迟栽培提供了理论依据。     

玉米昼夜节律钟基因CCA1的克隆及表达分析

昼夜节律钟基因CCA1在调解水稻和拟南芥的光周期反应中起着重要作用。本研究利用从水稻和拟南芥中分离到的CCA1基因序列作为靶序列BLAST获取Genbank中的信息,通过RT-PCR方法克隆获得了一条2326bp的玉米CCA1基因cDNA序列。BLAST比对发现其与水稻、大麦和拟南芥的序列相似性分别达73.7%、69.4%和39.8%。利用NCBI中的ORF Finder软件分析,发现该序列包含一个2163bp的开放阅读框,编码720个氨基酸残基,蛋白的分子量约为78819.17Da,等电点为6.468。推测其含有3个myb-DNA结合域、7个N-豆蔻酰化位点、1个G-box蛋白结合域以及1个蛋白跨膜结合域。采用实时荧光定量PCR分析发现,随光照时间的变化,该基因在玉米叶片中的表达量呈现出白天不断降低而夜晚逐渐升高的昼夜变化趋势。本研究为进一步研究玉米CCA1基因在调控玉米光周期敏感现象中的功能,阐明玉米光周期敏感机制提供了科学依据。     

人工延长光周期对大蒜抽薹的影响

以四川二水早为试验材料探究人工延长光周期对大蒜抽薹的影响。在大蒜花芽分化前2周喷施外源GA3后用400 W日光纳灯每天处理5 h补光40 d和单独采用400 W日光纳灯每天处理5 h补光40 d共2个处理,测定大蒜抽薹期生长量及可溶性糖、游离氨基酸、可溶性蛋白以及大蒜素等指标。结果表明,采用400 W日光纳灯每天处理5 h补光40 d可使大蒜抽薹提前20 d,大蒜品质差异不显著,游离氨基酸及大蒜素含量略有升高;喷洒外源GA3后人工延长光周期可使大蒜的抽薹提前30 d,蒜薹及蒜头产量差异不显著,但干物质含量较对照提高2%和8%,促进可溶性糖和可溶性蛋白质的合成。从本试验可以得出,人工延长光周期可以满足大蒜抽薹对光周期的要求,促进大蒜的早期抽薹,喷施外源GA3能诱导相关酶的合成,打破休眠,显著促进大蒜早期抽薹。     

大豆GmPic基因的分离及表达分析

对光敏感型大豆品种“中豆24”进行长日、短日和自然光3种光周期处理,采用cDNA-AFLP的方法筛选差异片段,并进一步通过RACE技术分离了该基因。该基因全长983 bp,包含一个完整的开放阅读框,编码248个氨基酸,在遗传关系上与线粒体磷酸盐转运蛋白高度同源。通过半定量RT-PCR对该基因在不同光周期中的表达模式进行分析,结果表明,该基因在大豆生长发育的早期阶段表达,短日照抑制其表达,而长日照则增强其表达。因此,大豆线粒体磷酸盐转运蛋白基因可能是作为一种负调控因子参与大豆光周期反应。对大豆线粒体磷酸盐转运蛋白基因的研究能为进一步阐明大豆光周期反应分子机理打下基础。     

光周期与温度对紫花苜蓿phyA和phyB mRNA表达的影响

通过探讨不同温度和不同光周期对紫花苜蓿(Medicago sativa L.)phyA和phyB mRNA含量的影响,以期为揭示调控苜蓿秋眠性的分子机理提供科学依据。试验采用FQ-PCR SYBR-Green I方法,测定了每天8,12和16h光照处理条件下3种秋眠类型苜蓿WL-232(秋眠型,FD2)、ArcherⅡ(半秋眠型,FD5)、WL-525(非秋眠型,FD8)的phyA和phyB mRNA表达水平;采用半定量RT-PCR,测定了5℃,15℃,25℃和35℃条件下秋眠型苜蓿Vernal(FD2)的phyA和phyB mRNA表达水平。结果表明:苜蓿存在光周期效应,短日照条件下秋眠型苜蓿phyB mR-NA表达量最大,相同光照条件下不同秋眠型苜蓿的表达规律为秋眠型>半秋眠型>非秋眠型,且相对于phyA,在紫花苜蓿绿叶中phyB对光周期的变化反应更敏感。在不同温度条件下秋眠型苜蓿Vernal的phyA和phyB合成规律不一致,低温条件下,phyB表达量较高,phyA表达量较低;高温条件下,phyA表达量较高,phyB表达量较低。上述结果表明phyB在调控苜蓿秋眠中发挥了更重要的作用。