We examined several aspects of nectar production in Campsis radicans to better understand how standing crop is affected and how production affects pollinator visitation. In all experiments, nectar and concentration of flowers were measured and total sugar was calculated. Flowers do not produce additional nectar unless nectar is removed, and it is not resorbed. Volume of standing crop and total sugar fluctuates throughout the day, whereas concentration remains constant. Age and time of day significantly affect regeneration of nectar and sugar. The number of removals did not significantly affect the amount of nectar or sugar regenerated; however, concentration declined significantly after the initial removal. We have established several factors affecting nectar production, although clearly there are other aspects influencing the production of nectar in C. radicans. Focus should be placed on determining the physiological aspects of secretion as well as studying the role that environmental factors have on physiological aspects.

Pollination success of animal-pollinated flowers depends on rate of pollinator visits and on pollen deposition per visit, both of which should vary with the pollen and nectar "neighborhoods" of a plant, i.e., with pollen and nectar availability in nearby plants. One determinant of these neighborhoods is per-flower production of pollen and nectar, which is likely to respond to environmental influences. In this study, we explored environmental effects on pollen and nectar production and on pollination success in order to follow up a surprising result from a previous study: flowers of Ipomopsis aggregata received less pollen in years of high visitation by their hummingbird pollinators. A new analysis of the earlier data indicated that high bird visitation corresponded to drought years. We hypothesized that drought might contribute to the enigmatic prior result if it decreases both nectar and pollen production: in dry years, low nectar availability could cause hummingbirds to visit flowers at a higher rate, and low pollen availability could cause them to deposit less pollen per visit. A greenhouse experiment demonstrated that drought does reduce both pollen and nectar production by I. aggregata flowers. This result was corroborated across 6 yr of variable precipitation and soil moisture in four unmanipulated field populations. In addition, experimental removal of pollen from flowers reduced the pollen received by nearby flowers. We conclude that there is much to learn about how abiotic and biotic environmental drivers jointly affect pollen and nectar production and availability, and how this contributes to pollen and nectar neighborhoods and thus influences pollination success.

A disponibilidade e distribuição espaço-temporal do néctar nos diferentes tipos vegetacionais está relacionada a diversos fatores. Em espécies nectaríferas, o néctar é o recurso principal disponibilizado aos visitantes florais e sua produção pode determinar o sucesso no fluxo de pólen entre indivíduos na população. Nesse estudo, os objetivos foram: (i) avaliar se o display floral e seus caracteres morfológicos estão associados à produção do néctar; (ii) verificar se a distribuição do néctar é concentrada ou uniformemente distribuída ao longo do ano e; (iii) como a produção do néctar atua na atração dos visitantes florais e na deposição intra e interespecífica de pólen no estigma em espécies de plantas nectaríferas. O estudo foi feito em vegetação de cerrado na Estação Ecológica de Jataí (EEJ), localizada em Luís Antônio, São Paulo. Na EEJ, nós demarcamos duas transeções de 500 m por 10 m de cada lado. As transeções foram percorridas quinzenalmente no período de agosto de 2013 a julho de 2014 e para cada espécie de planta nectarífera em floração, nós contamos o número de indivíduos e de flores produzidas/indivíduo (display floral). Nós encontramos que há interação significativa entre o tamanho e a forma da flor na produção do néctar (F = 40,48, p < 0,0001). Nós observamos que quanto maior o número médio de óvulos de uma dada espécie, maior a produção média de néctar por flor (Rs = 0,58; p < 0,05). Encontramos que a razão pólen intraespecífico/pólen total depositado no estigma das flores foi influenciada negativamente pela abundância das abelhas (t= -3,930; p= 0,005). Nós observamos um nível intermediário de especialização (H2 = 0,412) quando analisamos a interação entre as espécies nectaríferas e as abelhas visitantes por meio de observação direta e mais especializado quando analisamos a interação por meio dos grãos de pólen depositados no corpo das abelhas (H2 = 0,62). Nós encontramos uma interação altamente especializada quando avaliamos os grãos de pólen depositados nos estigmas (H2 = 0,943). Nós corroboramos as nossas hipóteses de que a produção e distribuição do néctar na comunidade estão associadas ao número de flores disponíveis e à morfologia floral das espécies nectaríferas e que as plantas que produzem mais flores e um maior volume de néctar, apresentaram mais óvulos e atraem um maior número de abelhas visitantes e consequentemente apresentam uma maior deposição polínica nos estigmas / The availability and the spatial and temporal distribution of nectar in different types of vegetation are related to several factors. In nectariferous species, nectar is the main resource available to floral visitors and its production can determine a successful pollen flow between individuals in the population. The present study aimed to: (i) assess whether the floral display and its morphological traits are associated with nectar production; (ii) verify whether the distribution of nectar is concentrated or evenly distributed throughout the year and; (iii) analyze the influence of nectar production in attracting floral visitors and on intra and interspecific deposition of pollen on the stigma in nectariferous plant species. The study was conducted in cerrado in the Jataí Ecological Station (EEJ), located in Luís Antônio, São Paulo State. Inside the EEJ, two transects measuring 500 m x 10 m were delimited. The transects were run every two weeks from August 2013 to July 2014 and the number of individuals and flowers produced/individual (floral display) were counted for each species of nectariferous plant at flowering. There was a significant interaction between the size and shape of the flower for nectar production (F = 40.48, p < 0.0001). The higher the average number of ovules of a given species, the greater the average production of nectar per flower (Rs = 0.58; p < 0.05). Also, the ratio intraspecific pollen/total pollen deposited on the stigma of flowers was negatively affected by the abundance of bees (t= -3.930; p= 0.005). An intermediate level of specialization (H2 = 0.412) was found when analyzing the interaction between nectariferous species and visiting bees through direct observation and a more specialized level when analyzing the interaction by means of pollen grains deposited on the body of bees (H2= 0.62). In turn, considering the pollen grains deposited on stigmas, a highly specialized interaction was recorded (H2= 0.943). Our following hypotheses were confirmed: the production and distribution of nectar in the community are associated with the number of available flowers and with floral morphology of the nectariferous species and plants producing more flowers and a greater volume of nectar present more ovules and attract a higher number of visiting bees and thus show a greater deposition of pollen on stigmas

A disponibilidade e distribuição espaço-temporal do néctar nos diferentes tipos vegetacionais está relacionada a diversos fatores. Em espécies nectaríferas, o néctar é o recurso principal disponibilizado aos visitantes florais e sua produção pode determinar o sucesso no fluxo de pólen entre indivíduos na população. Nesse estudo, os objetivos foram: (i) avaliar se o display floral e seus caracteres morfológicos estão associados à produção do néctar; (ii) verificar se a distribuição do néctar é concentrada ou uniformemente distribuída ao longo do ano e; (iii) como a produção do néctar atua na atração dos visitantes florais e na deposição intra e interespecífica de pólen no estigma em espécies de plantas nectaríferas. O estudo foi feito em vegetação de cerrado na Estação Ecológica de Jataí (EEJ), localizada em Luís Antônio, São Paulo. Na EEJ, nós demarcamos duas transeções de 500 m por 10 m de cada lado. As transeções foram percorridas quinzenalmente no período de agosto de 2013 a julho de 2014 e para cada espécie de planta nectarífera em floração, nós contamos o número de indivíduos e de flores produzidas/indivíduo (display floral). Nós encontramos que há interação significativa entre o tamanho e a forma da flor na produção do néctar (F = 40,48, p < 0,0001). Nós observamos que quanto maior o número médio de óvulos de uma dada espécie, maior a produção média de néctar por flor (Rs = 0,58; p < 0,05). Encontramos que a razão pólen intraespecífico/pólen total depositado no estigma das flores foi influenciada negativamente pela abundância das abelhas (t= -3,930; p= 0,005). Nós observamos um nível intermediário de especialização (H2 = 0,412) quando analisamos a interação entre as espécies nectaríferas e as abelhas visitantes por meio de observação direta e mais especializado quando analisamos a interação por meio dos grãos de pólen depositados no corpo das abelhas (H2 = 0,62). Nós encontramos uma interação altamente especializada quando avaliamos os grãos de pólen depositados nos estigmas (H2 = 0,943). Nós corroboramos as nossas hipóteses de que a produção e distribuição do néctar na comunidade estão associadas ao número de flores disponíveis e à morfologia floral das espécies nectaríferas e que as plantas que produzem mais flores e um maior volume de néctar, apresentaram mais óvulos e atraem um maior número de abelhas visitantes e consequentemente apresentam uma maior deposição polínica nos estigmas / The availability and the spatial and temporal distribution of nectar in different types of vegetation are related to several factors. In nectariferous species, nectar is the main resource available to floral visitors and its production can determine a successful pollen flow between individuals in the population. The present study aimed to: (i) assess whether the floral display and its morphological traits are associated with nectar production; (ii) verify whether the distribution of nectar is concentrated or evenly distributed throughout the year and; (iii) analyze the influence of nectar production in attracting floral visitors and on intra and interspecific deposition of pollen on the stigma in nectariferous plant species. The study was conducted in cerrado in the Jataí Ecological Station (EEJ), located in Luís Antônio, São Paulo State. Inside the EEJ, two transects measuring 500 m x 10 m were delimited. The transects were run every two weeks from August 2013 to July 2014 and the number of individuals and flowers produced/individual (floral display) were counted for each species of nectariferous plant at flowering. There was a significant interaction between the size and shape of the flower for nectar production (F = 40.48, p < 0.0001). The higher the average number of ovules of a given species, the greater the average production of nectar per flower (Rs = 0.58; p < 0.05). Also, the ratio intraspecific pollen/total pollen deposited on the stigma of flowers was negatively affected by the abundance of bees (t= -3.930; p= 0.005). An intermediate level of specialization (H2 = 0.412) was found when analyzing the interaction between nectariferous species and visiting bees through direct observation and a more specialized level when analyzing the interaction by means of pollen grains deposited on the body of bees (H2= 0.62). In turn, considering the pollen grains deposited on stigmas, a highly specialized interaction was recorded (H2= 0.943). Our following hypotheses were confirmed: the production and distribution of nectar in the community are associated with the number of available flowers and with floral morphology of the nectariferous species and plants producing more flowers and a greater volume of nectar present more ovules and attract a higher number of visiting bees and thus show a greater deposition of pollen on stigmas

Urban landscapes can support pollinator conservation, but traditional landscape designs lack the diverse mixtures of native plants needed to support native pollinators. Although native plants support pollinators and can survive with less water and fertilizer than non-native landscape plants, they do not always grow well under modified urban soil conditions and irrigation regimes. A better understanding of the factors influencing flower production and the quality of native plants is needed if we are to design landscapes that support pollinator conservation. This study focused on how flower production and quality in different native plants responded to compost and irrigation treatments. The experiment consisted of 27 native plant species grown in sixteen 6.1 x 9.1 m plots with or without compost and with regular or as-needed irrigation in a randomized complete block design. We quantified total flower production and examined nectar production and flower size in select plant species. Results showed that compost addition greatly increased flower production and that the floral traits of individual plant species varied in their response to compost additions and different irrigation regimes. Unraveling the complexities of these interactions is important for designing urban landscapes that support pollinator conservation.