雪莲的开花生物学特性及其生态适应意义

雪莲(Saussurea involucrata)是一种典型的高山草本植物, 同时也是我国重点保护的珍稀药用植物。该文对雪莲的开花生物学特性及其对高山环境的适应策略进行了观测与分析。主要结果如下: 雪莲不育花序单生于茎生叶的叶腋内, 可育复头状花序生长于茎顶端, 由26 ± 7个头状花序构成, 每个花序的小花数为137 ± 34个。复头状花序外侧为绿色至淡黄色半透明的茎生苞叶所包被, 开花过程中, 白天茎生苞叶内侧温度和湿度明显高于外侧的温度和湿度, 最大温差达7.2 ℃, 最大相对湿度差达54.2%, 可为苞叶内侧花序中小花的传粉和受精以及胚和种子的发育提供良好的微环境。不同年份间雪莲的开花物候差异不显著(p > 0.05), 群体花期为65-75天, 单株花期为45-55天, 盛花期持续时间约35天, 平均每株每天开花数为201个, 属于集中开花模式, 有利于吸引传粉者。单花开放持续时间为4-6天, 小花泌蜜持续时间为3天, 其泌蜜量与糖浓度于每天 12:00时达到最高值, 但随着开花的持续, 日泌蜜量逐渐增加, 而糖浓度逐渐减少。雪莲花期浓郁的气味、聚合成复头状的可育花序及其紫色小花与充足的泌蜜量, 增加了对传粉者的吸引力。雪莲开花过程中存在的雌雄异位、雄性先熟以及被动式花粉次级展现现象, 减少了自花授粉的可能性。自然条件下, 其头状花序的结籽数和结籽率分别为126.0 ± 10.5粒和91.7% ± 4.2%, 单株结籽数为3 326.4 ± 28.7, 表明雪莲在高山极端环境中能顺利地完成有性生殖过程。     

白桦和紫椴树干非结构性碳水化合物的空间变异

以中国东北温带森林两个散孔材树种白桦和紫椴为对象,研究落叶后树干木质部中非结构性碳水化合物(NSC)浓度的空间变异.结果表明: 两种树种的可溶性糖与淀粉的总和(TNC)与可溶性糖浓度均随树干径向深度增加而缓慢下降,淀粉的径向变化不明显,即使在树干径向深处仍存有大量的NSC.两种树种树干的TNC、可溶性糖和淀粉浓度从根颈到胸高降低,之后逐渐升高,最大值出现的高度因树种和TNC组分而异.两种树种树干糖淀粉比值的纵向变化趋势为：白桦随树干升高而增大,紫椴则随之减小.树干NSC储量估算的误差主要来源于NSC浓度的纵向变化,其次是径向变化.喜光树种白桦的树干TNC浓度(1.0%干质量)显著低于耐阴树种紫椴(4.3%干质量),可能与其生活史对策差异有关.采用考虑了树干NSC纵向和径向变化的取样方法,可以有效地降低树木或林分水平上NSC储量估算的不确定性.
     

濒危植物矮沙冬青开花物候研究

对矮沙冬青(Ammopiptanthus nanus Cheng f.)的形态学特征、开花物候及花空间分布进行了研究,结果表明:在单花、花序、单株、居群水平上的开花物候都表现出很强的开花不同步性,在单花、单花序水平主要表现在单花寿命4~9 d不等,平均(6.74±1.23)d,以7 d出现的频率最高;单花序开花持续时间范围在4~13 d,平均(8.33±2.63)d,以10 d出现的频率最高;单株及居群水平上表现更为明显.矮沙冬青的花具有虫媒传粉的特征,花主要分布在花枝的上部,下部花所占比例很小,有很多花枝花全部为上部花.相关性分析表明上部花和总花数相关性极显著(r=0.990,P<0.01),而中部花、下部花和总花数的相关性不显著,甚至呈负相关.单株不同方位开花数量差异不显著(F=0.0579,P>0.05).     

黑松人工林生物量结构的数学模型

本文对蚌埠市郊黑松人工林生物量和生产力进行了系统测定和分析。林分的总生物量为64.604_t·ha~(-1)．地上部分为49.69_a·ha~(-1),占总生物量的76.9％;地下根系仅为14.914_t·ha~(-1)。并建立了估测黑松人工林各器官生物量的数学模型;W_T=0.1279D~(2.3599)、W_A=0.0462（D~2H）~(0.9446)、W_S=0.00957D~(2.2926)、W_(BR)=0.006（D~2H）~(1.2958)、W_L＝O.0276D~(1.7541)、W_(BK)＝0.0135（D~2H）~(0.873)、W_R＝0.0196D~(3.5023)、W_T＝-6.410＋11.950W_L。黑松人工林平均单株年净生长量为1.532kg·ha~(-1)·a~(-1),仅为同地区马尾松人工林生长量3.01kg·ha~(-1)·a~(-1)的一半。引起黑松人工林生长量低和生物量少的主要原因是黑松人工林针叶量少,生态环境不适宜黑松人工林生长。目前应对低产黑松林进行改造,无力改造的地区要保持林分较大密度,以提高林分的总生长量。     

天然枫桦红松林凋落量动态及养分归还量

三年定位研究表明小兴安岭天然枫桦红松林年均凋落量有5.8t／ha(干重)。凋落量的季节变化格局是随着气候变冷有一明显秋季凋落高峰期(9—10月)。凋落物每年养分的归还量：Ca、N、K、Mg、P,相应为67.0、56.9、14.8、9.5、和6.6kg／ha,总计155.0kg／ha。据测定阔叶树落叶养分含量明显高于所有针叶的含量。尽管阔叶树的年凋落量仅占该混交林的年总凋落量的三分之一,阔叶树落叶仍有相当高的养分比例(43.4%)归还土壤。因此,红松林分的经营管理中,保留适当比重的阔叶树有利于土壤改良和促进林分生长。     

安徽长江滩地杨树人工林生物量和养分积累

安徽长江外滩Ⅰ-69杨树无性系人工林11年林分生物量达到90.2t·hm^-2,平均生产量为8.2t·hm^-2·a^-1,平均单株生产量为21.9kg·a^-1,与相同纬度带一般立地条件林分相比单株生产量高0.7%;另外林分叶面积指数为3.32m²·m^-2,造林后第3年叶面积指数的净增值达到最高,同时林分生产力开始进入最高水平该林分每生产1t干物质需要N 3.369kg、P 0.327kg、K 2.424kg、Ca 7.465kg、Mg 0.2kg、Cu 0.0073kg、Mn0.01868kg、Fe 0.1115kg和Zn 0.00268kg,同时吸收S 0.72kg、Cr 0.000252kg、Cd 0.0O039kg和Pb0.00043kg.年轮中元素含量逐年有波动,N和K呈负相关,而N与P则表现为正相关;滩地的淹水时间对年轮中P含量影响较大,其次是N,与K含量呈负相关,但不显著.     

濒危植物金花茶开花物候和生殖构件特征

对桂林雁山迁地保护的金花茶(Camellia nitidissima)开花物候和生殖构件特征进行了研究.结果表明:(1)单花开放过程可分为蕾松、初开、盛开、落花4个阶段,单花寿命约2～8 d;(2)个体花期长,始花时间变异大,单株花期平均为37 d,始花时间可相差2个多月,种群始花时间为1月上旬,3月上旬达到开花高峰期,花期持续近3个月;(3)生殖构件的数量与个体径级和树冠层次有一定关系,地径大于6 cm的个体,其单株花数、生殖枝数、生殖枝比率显著高于地径小于4 cm和4～6 cm个体,而每生殖枝花数则无显著差异;不同树冠层次之间,平均生殖枝数和生殖枝比率,以中、下层显著高于上层,而每生殖枝花数以上层最高,花数在不同冠层之间无显著差异;(4)花芽期败育率为16.33%,花期败育率为63.05%,果期败育率为44.09%,败育率在不同径级个体和不同冠层之间有一定差异;败育率高,结实率低,种子产量少,是金花茶濒危的一个主要原因;(5)开花数目与花期长度呈正相关,个体始花时间与花期长度、座果率之间存在显著的负相关关系.     

碱蓬对不同盐度富营养化模拟海水的净化效应及其生长特性

研究了碱蓬﹝Suaeda glauca (Bunge) Bunge﹞对不同盐度(质量浓度8、16和24 g·L-1NaCl)富营养化模拟海水中总氮( TN)和总磷( TP)的净化效果,并对碱蓬生长及其不同部位TN和TP的含量和积累量进行了研究。结果表明：碱蓬在质量浓度8、16和24 g·L-1 NaCl富营养化模拟海水中均生长良好。随处理时间的延长,种植碱蓬后不同盐度富营养化模拟海水中TN和TP浓度均逐渐降低,TN和TP去除率均逐渐升高,其中在质量浓度16 g·L-1 NaCl富营养化模拟海水中TN和TP去除率最高。处理25 d,在质量浓度16 g·L-1 NaCl富营养化模拟海水中碱蓬单株鲜质量、单株干质量和株高的增量以及平均须根长均最大,单株总干质量最高,均显著高于其他2个处理组;质量浓度16 g·L-1 NaCl富营养化模拟海水中碱蓬单株叶、茎和根中的TN和TP积累量明显高于其他2个处理组,而单株种子中的TN和TP积累量则随着NaCl质量浓度提高而降低。研究结果显示：作为在滨海盐渍化土壤中生长的一年生优势物种,碱蓬可以有效地对有一定盐度的富营养化水体进行生物修复,具有对滩涂养殖废水进行生物改良和修复的潜力。     

基于热比率法的青海云杉林蒸腾量估算

流域上游森林蒸腾量的准确估算对于干旱区水资源管理至关重要。该文采用热比率法的树干液流技术对青海云杉(Picea crassifolia)单木和林分蒸腾量进行了估算和转换, 目的在于通过该研究为不同尺度森林蒸腾量估算提供一个系统的解决方案。研究结果如下: 第一, 青海云杉胸径与边材面积间存在显著指数函数关系, R² = 0.94, p < 0.000β1; 第二, 热比率法的青海云杉蒸腾量测量中, 理论值与观测值间的比例系数为1.09, 观测值偏小; 第三, 基于单木平均液流速率和林分总边材面积的林分蒸腾量计算中, 不同胸径样树液流速率的异质会导致液流速率被高估或低估近1/3; 第四, 基于单木胸径与液流量间关系的林分液流估算技术能够更合理地对青海云杉蒸腾量进行估算。根据该文研究结果, 基于探针式液流测量技术可以更为科学地对单一树种研究区不同尺度的蒸腾量进行估算。     

不同施肥处理对甜菊生长及糖苷含量和积累量的影响

采用盆栽法,以甜菊( Stevia rebaudiana Bertoni)品种‘中山4号'(‘Zhongshan No.4')当年生扦插苗为研究对象,研究不同形态氮肥(硫酸铵、硝酸钠和尿素)及不同施氮量(纯氮)、施磷量( P2 O5)和施钾量( K2 O)对幼苗生长及糖苷含量和单株积累量的影响。结果显示：随氮肥、磷肥和钾肥施用量的提高,甜菊幼苗的株高、茎粗、叶长、叶宽、单株叶干质量和单株茎干质量均呈先升后降的变化趋势,且总体上与对照无显著差异,仅施磷量300 mg·kg-1处理组的叶长显著高于对照;根据施肥量与单株叶干质量的回归方程,确定硫酸铵、硝酸钠、尿素、磷肥和钾肥的施用量分别为64.87、660.21、735.84、211.54和775.92 mg·kg-1时,幼苗单株叶干质量最高。在硫酸铵处理组中,300 mg·kg-1处理组甜菊叶片中的莱鲍迪苷A( R-A)含量及甜菊苷( St)、R-A和总苷的单株积累量以及600 mg·kg-1处理组的St单株积累量高于对照,多数处理组的St、R-A和总苷含量及单株积累量均低于对照;在硝酸钠处理组中,1200 mg·kg-1处理组的R-A和总苷含量、600和900 mg·kg-1处理组的St单株积累量以及300~900 mg·kg-1处理组的R-A和总苷单株积累量高于对照,其他处理组的St、R-A和总苷含量及单株积累量均低于对照;在尿素处理组中,1500 mg·kg-1处理组的R-A和总苷的含量和单株积累量以及600和900 mg·kg-1处理组的R-A和总苷单株积累量高于对照,其他处理组的St、R-A和总苷含量及单株积累量均低于对照;各施氮处理组中,仅1500 mg·kg-1处理组的R-A含量与对照差异显著,其他指标均与对照无显著差异。在施磷处理组中,100 mg·kg-1处理组的R-A含量以及100和200 mg·kg-1处理组的St、R-A和总苷的单株积累量高于对照,多数处理组的St、R-A和总苷含量及单株积累量低于对照且与对照均无显著差异。在施钾处理组中,各处理组的St、R-A和总苷含量及单株积累量均高于对照,其中仅900 mg·kg-1处理组的St、R-A和总苷含量与对照显著差异。各施肥处理组的St含量占总苷含量的百分率均低于对照、R-A含量占总苷含量的百分率均高于对照,且总体上与对照无显著差异。经过综合分析,建议在甜菊生育期内的施肥量为纯氮600~900 mg·kg-1、P2 O5200~300 mg·kg-1和K2 O 600~900 mg·kg-1,其中氮肥以尿素为宜。     

Quantifying the canopy nectar resource and the impact of logging and climate in spotted gum Corymbia maculata forests

Nectar in tall forest canopies is a significant, but unquantified resource for Australian fauna. We investigated the impact of logging on nectar production in the canopy of spotted gum Corymbia maculata in southern New South Wales. In addition, we quantified the magnitude of canopy nectar production and how this varied with climate over 2 years. In 2005 flowers were bagged on large and small trees in replicate recently logged, regrowth and mature forest. Neither logging history nor tree size significantly affected overnight nectar production per flower, although there was a significant interaction. When nectar production was scaled up to the forest stand (incorporating flower and tree density) mature forest produced almost 10 times as much sugar per ha as recently logged forest, with regrowth being intermediate. Under current forest practices at the compartment scale, the difference between mature forest and recently logged forest was reduced to a factor of two times. One distinctive characteristic of C. maculata nectar in 2005 was its high sugar content (40–60%) compared with the concentrations measured in 2003 (～18%). Nectar was only slightly depleted in unbagged flowers in 2005 when flowering was unusually extensive. We estimated that, on average, mature spotted gum forest produced a vast resource of nectar overnight: 35 000 Kj ha^?1. Flowers measured in 2003 provided a strong contrast with only occasional stands of trees flowering, much less sugar per flower early in the morning and unmeasurable quantities by mid‐morning, indicating that nectar was limiting. Measurements at sites in 2003 indicated that regrowth sites could be more productive than mature forest; however, few sites were measured. We suggest that management should focus mitigations on poor flowering years when the nectar resource is limiting. Models of nectar production collated over both years, using climate and site variables, indicated nectar volumes and sugar concentration respond differently to environmental conditions. Predicting the nectar resource, which is made up of both components, was most consistently related to recent conditions that were unfavourable to foliage production.     

Nectar secretion dynamics and honey production potentials of some major honey plants in Saudi Arabia

The contribution of a bee plant species to honey production depends on the plant’s nectar secretion quality and quantity, which is mainly governed by biotic and abiotic factors. The aim of the current study, was to investigate the nectar secretion dynamics and honey production potential of 14 major bee plant species of the target area. We examined the quantity and dynamics of nectar sugar per flower five times a day using a nectar sugar washing technique and direct measuring of nectar with calibrated capillary tubes. The average nectar sugar amount of the species varied from 0.41 mg/flower to 7.7 mg/flower (P < 0.0001). The honey sugar per flower was used to extrapolate the honey production potential per plant and per hectare of land. Accordingly the honey production potential of the species observed to vary from 14 kg/hectare in Otostegia fruticosa to 829 kg/hectare in Ziziphus spina-christi. The nectar secretion dynamics of the species generally showed an increasing trend early in the morning, peaking toward midday, followed by a decline but different species observed to have different peak nectar secretion times. Generally, the tree species secreted more nectar sugar/flower than the herbs. The nectar secretion amount of the species was positively correlated with the ambient temperature, indicating the adaptation of the species to hot climatic conditions. However, different species were observed to have a different optimum temperature for peak nectar secretion. Despite the limited rainfall and high temperature of the area, many plants were found to have good potential for honey production. The monetary value of honey per hectare of the studied honeybee plant species can be of equal or greater than the per-hectare monetary value of some cultivated crops that require numerous inputs. In addition, the information generated is believed to be useful in apiary site selection and to estimate the honey bee colony carrying capacity of an area.     

Reproductive biology, variability of nectar features and pollination of Combretum fruticosum (Combretaceae) in Argentina

Flower morphology, nectary structure, nectar features (chemical composition, secretion pattern, standing crop, removal effects) and flower visitors are analysed in an Argentinian population of Combretum fruticosum. The variability of these data was examined throughout the flower lifetime. Nectar is hexose dominant. Its chemical composition and concentration are constant for all flowering stageS. Nectar volume varies as a function of flower age due to a combination of nectar secretion, cessation and resorption periods. The overall sugar production is decreased by nectar removal. The plant is self-incompatible and xenogamouS. Only 16.2% of the flowers set seedS. Inflorescences with green flowers were exclusively visited by two hummingbird and three perching bird species which transfer the pollen. A clear link was observed among nectar production pattern, standing crop of nectar, and visitors' behaviour.     

Phylogenetic analysis of interspecific variation in nectar of hummingbird-visited plants

We tested whether phylogeny, flower size and/or altitude were significant predictors of interspecific variation in nectar production of hummingbird-visited plants in an assembled database (289 species, in 22 orders, 56 families and 131 genera). Although the study is focused on hummingbird-pollinated plants (241 plant species), plants with different pollinator syndromes (48 species) are also included in the analyses. Nectar volume secreted in a given time period (usually 24 h) by a given flower, its sugar concentration and corolla length were compiled mainly from the literature. Altitude was also obtained from the original references. Sugar production was computed basically as the product of nectar secretion and sugar concentration, and expressed on a per 24-h basis. All nectar traits and corolla length (all log transformed), as well as altitude, showed statistically significant phylogenetic signal. Both nonphylogenetic and phylogenetically informed (independent contrasts) analyses indicated a highly significant positive correlation between corolla length and both nectar volume and sugar production. In addition, altitude (which is partially a surrogate for temperature) was significantly negatively correlated with both sugar concentration and production. Possible reasons for coadaptation of nectar production and sugar production with corolla length are discussed.     

Nectar Secretion Pattern and Removal Effects in Six Argentinean Pitcairnioideae (Bromeliaceae)

Nectar secretion pattern and effects of nectar removal were analyzed in six hummingbird-pollinated Argentinean Pitcairnioideae: Abromeitiella brevifolia. A. lorentziana, Deuterocohnia longipetala. Dyckia floribunda, D. ragonesei and Puya spathacea. Flower lifetime was determined in each case. Nectar volume, concentration and sugar production were measured from bud opening till fading of flowers at different time intervals according to the species' flower life-span. Nectar volume varies while nectar concentration and cumulative sugar production increase as a function of flower age in all the studied species. In general, total nectar volume and concentration values can be affected by periodic removal, but total sugar production is unaffected. Only in Puya spathacea did periodic nectar harvesting reduce the total amount of sugar produced.     

An examination of nectar production in 34 species of Dendrobium indicates that deceptive pollination in the orchids is not popular

Nectar, the most common floral reward, is generally used to determine whether an orchid species involves deceptive pollination. Estimates of the deceptive pollination systems with nectarless flowers have ranged from one quarter to one third of the nearly 30 000 species of orchids. These estimates, however, are biased towards temperate-zone, usually terrestrial, orchids. Here we investigated nectar production and property in 34 epiphytic orchid species of the Southeast Asian genus Dendrobium. Twenty-one species were observed producing nectar. The amount and sugar concentration (in bagged flowers) of 12 species varied from 0.45 to 2.78 μL and from 8.1% to 31.1%. The nectar was sucrose-dominant, typical of bee-pollinated flowers. Reconstruction of phylogenetic relationship indicated that transition of nectar secretion occurred in the genus. Spur length was positively correlated with flower size but species with relatively long spurs tended to produce small volume of nectar. Nectar production was strikingly variable among and within individuals in some species, suggesting that a vital measurement of bagged and fresh flowers is needed. Given that the quantitative measurement of nectar or floral reward in orchid species remains scarce, an estimate of deceptive pollination systems awaits further survey in diverse genera.     

A preliminary study of nectar production of the field cress,Rorippa indica,in relation to the age of its flowers

Floral nectar production quantity and changes in sugar concentration of the nectar ofRorippa indica were investigated. Flowers were sorted by age. The small flower size was a major factor for the use of BCG test paper in nectar sampling. In flowers of the youngest age category, the nectar volume increased toward the night and decreased during the day. The amount of sugar in the nectar decreased with flower age. The sugar concentration was lower at night than daytime. The variability and changes in nectar concentration enabled various species of insects to forage for nectar.     

Nectar Dynamics and Sugar Composition in Flowers of Silene and Saponaria Species (Caryophyllaceae)

Abstract: Nectar production in Saponaria officincilis and in five species of Silene (S. ciba, S. dioica, S. noctiflora, S. nutans, S. vulgaris ) was examined during two consecutive years (May to July 1993, and May to June 1994) in the Botanical Garden of the University of Giessen. Nectar volume and sugar concentration were studied in relation to time of day, flower sex, flower age, and flowering stage. Nectar amount in all species studied (except S. dioica ) increased in the afternoon or in the evening until midnight (or until the early morning in S. nutans ). After midnight and until midday, nectar volume in non-visited flowers (except S. dioica ) decreased. Nectar volume in non-visited S. dioica flowers increased constantly with flower age, indicating a stable nectar secretion rate, possibly favouring both day- and night-active flower visitors. Even at the time of highest nectar secretion, all species studied presented several nectarless flowers. Sucrose dominance in the nectar of the nocturnal species S. nutans and Saponaria officinalis fits well with the general syndrome of flowers pollinated by hawkmoths. The syndrome also applies to the nocturnal but regularly selfing, S. noctiflora . The more generalis-tic species S. dioica and S. vulgaris , which are regularly visited by bumblebees as well as nocturnal moths, secreted hexose-domi-nant nectar. Unexpectedly, Silene alba , the only nocturnal species that strictly excluded day-active flower visitors by closing flowers during the day, also secreted hexose-dominant nectar. In some cases, nectar volumes and nectar concentration differed significantly between hermaphroditic, male, and female flowers. Female flowers of S. alba, S. dioica , and S. nutans contained significantly less concentrated nectar than male or hermaphroditic ( S. nutans ) ones. In S. noctifiora and S. vulgaris the difference was not statistically significant but nectar concentration did show the same tendency.     

Floral nectaries, nectar production dynamics and chemical composition in six ipomoea species (convolvulaceae) in relation to pollinators

BACKGROUND AND AIMS: Floral nectaries and nectar features were compared between six Argentinian Ipomoea species with differences in their pollinator guilds: I. alba, I. rubriflora, I. cairica, I. hieronymi var. hieronymi, I. indica, and I. purpurea. METHODS: Pollinators were recorded in natural populations. The morpho-anatomical study was carried out through scanning electron and light microscopy. Nectar sugars were identified via gas chromatography. Nectar production and the effect of its removal on total nectar sugar amount were determined by using sets of bagged flowers. KEY RESULTS: Hymenopterans were visitors of most species, while hummingbirds visited I. rubriflora and sphingids I. alba. All the species had a vascularized discoidal nectary surrounding the ovary base with numerous open stomata with a species-specific distribution. All nectar samples contained amino acids and sugars. Most species had sucrose-dominant nectars. Flowers lasted a few hours. Mean nectar sugar concentration throughout the lifetime of the flower ranged from 34.28 to 39.42 %, except for I. cairica (49.25 %) and I. rubriflora (25.18 %). Ipomoea alba had the highest nectar volume secreted per flower (50.12 microL), while in the other taxa it ranged from 2.42 to 12.00 microL. Nectar secretion began as soon as the flowers opened and lasted for a few hours (in I. purpurea, I. rubriflora) or it was continuous during the lifetime of the flower (in the remaining species). There was an increase of total sugar production after removals in I. cairica, I. indica and I. purpurea, whereas in I. alba and I. rubriflora removals had no effect, and in I. hieronymi there was a decrease in total sugar production. CONCLUSIONS: The chemical composition, production dynamics and removal effects of nectar could not be related to the pollinator guild of these species. Flower length was correlated with nectary size and total volume of nectar secreted, suggesting that structural constraints may play a major role in the determination of nectar traits of these species.     

Variability of nectar production and composition in Linaria vulgaris (L.) Mill. (Scrophulariaceae)

 We studied nectar characteristics during the long flowering period (late June to end of November) in two populations of Linaria vulgaris (L.) Mill. spontaneously growing in the Botanical Gardens of Siena University (Tuscany, central Italy). The two populations were close to each other but they differed in blooming period. Plants of population 1 sprouted in May and flowered from the end of June to the end of September. Population 2 sprouted at the end of August and flowered from September to the end of November. Differences in nectar production and composition were found between and within populations. Flowers of population 1 produced a very small amount of nectar (not collectable) that remained on the nectary surface. The quantity of nectar increased in late September, when each flower produced 2–3 μl of nectar that flowed into the spur. Total sugar concentration was 175.8 mg/ml in young flowers. Flowers of population 2 produced 5–8 μl of nectar with a total sugar concentration of 200.9 mg/ml in the young stage. In bagged senescent flowers nectar volume decreased in both populations and nectar sugar concentration decreased down to 11.6 mg/ml in population 2 and increased up to 289.6 mg/ml in population 1. For both populations, the decrease in nectar volume in bagged flowers may have been due to water loss by evaporation. In population 2, the decrease in sugar concentration may have been due to nectar reabsorption that was never observed in population 1. Nectar variability is discussed in relation to insect visits and seed set. Received August 14, 2002; accepted December 17, 2002 Published online: June 2, 2003