Viability of pollen grains and stigma receptivity in Desert Rose

Adenium obesum (Forssk.) Roem. & Schult., popularly known as desert rose, has become a valuable ornamental plant. In floriculture, the production of hybrids is prioritized. Hence, knowledge on floral biology and sexual reproduction of the target species is fundamental. The objectives of this study were: (1) to test sucrose concentrations and temperatures for in vitro germination of A. obesum pollen grains; (2) to identify the effect of temperature on the viability of A. obesum pollen grains; and (3) to evaluate the viability of pollen grains and stigma receptivity in pre-anthesis, at flower opening, and 72 h post-flower opening in three accessions of A. obesum. A significant relationship between temperatures and sucrose concentrations was observed in the in vitro germination test. The highest percentage of in vitro germination of pollen grains, 39.81%, was observed at an estimated temperature of 26.05 °C. Desert rose accessions maintained in biochemical oxygen demand (BOD) chambers at 30 °C during a 16-h light photoperiod showed faster flowering, and temperatures ≥ 25 °C induced pollen grain viability percentages above 69%. Temperature is one of the most important abiotic factors, influencing mainly in pollen germination, pollen tube growing and in efficiency fertilization. The ICA-wd accession stood out and can be considered a pollen donor in artificial pollination. The stigmas of flowers were receptive from a day before flower opening until three days after. The two parameters presented above, stigma receptivity and pollen viability, allow inferences about the appropriate time for successful pollination and subsequent fertilization in desert roses.

Flowering Biological Characteristics of Camellia weiningensis Y.K. Li.

This study aimed to investigate the flowering biological characteristics, floral organ characteristics, and pollen morphology of Camellia weiningensis Y.K. Li. These features of adult C. weiningensis plants were observed via light microscopy and scanning electron microscopy (SEM). Pollen viability and stigma receptivity were detected using 2,3,5-triphenyltetrazole chloride (TTC) staining and the benzidine–hydrogen peroxide reaction method. C. weiningensis is monoecious, with alternate leaves and glabrous branchlets. Its flowering period lasts 2 to 4 months, and the flowering time of individual plants lasts ≈50 days, with the peak flowering period from the end of February to the middle of March. It is a “centralized flowering” plant that attracts a large number of pollinators. Individual flowers are open for 12 to 13 days, mostly between 1230 and 1630 hr, and include four to six sepals, six to eight petals, ≈106 stamens, an outer ring of ≈24.6-mm-long stamens, an inner ring of ≈13.4-mm-long stamens, one pistil, and nine to 12 ovules. The flowers are light pink. The style is two- to three-lobed and 16.6 mm long, showing a curly “Y” shape. The contact surface of the style is covered with papillary cells and displays abundant secretory fluid and a full shape, facilitating pollen adhesion. The pollen is rhombohedral cone-shaped, and there are germ pores (tremoids). The groove of the germ pore is slender and extends to the two poles (nearly reaching the two poles). The pollen is spherical in equatorial view and trilobate in polar view. The pollen vitality was highest at the full flowering stage, and the stigma receptivity was greatest on days 2 to 3 of flowering. The best concentration of sucrose medium for pollen germination was 100 g/L. The number of pollen grains per anther was ≈2173, and the pollen-to-ovule ratio was 23,034:1. C. weiningensis is cross-pollinated. Seventy-two hours after cross-pollination, the pollen tube reached the base, and a small part entered the ovary. The time when the pollen tube reached the base after pollination was later than that in commonly grown Camellia oleifera. The results of this study might lay an important foundation for the flowering management, pollination time selection, and cross-breeding of C. weiningensis.

Floral biology and breeding system of endangered species: Parmentiera cereifera Seem. (Bignoniaceae)

Parmentiera cereifera Seem. is an endangered species in the family Bignoniaceae. Related to the conservation effort, information about the reproductive biology of this species is very limited. Based on that, the objectives of this study were to provide knowledge about the reproductive properties such as floral biology and breeding system of P. cereifera. The research was conducted at Purwodadi Botanic Garden, from October 2019 to February 2021. Several important aspects of reproductive biology, including flower biology, pollen viability and stigma receptivity, pollen morphology and breeding system were investigated. The viability was tested with TTC (2, 3, 5–triphenly tetrazolium chloride) and stigma reseptivity was tested with hydrogen peroxide. The breeding system was determined based on outcrossing index (OCI) using Cruden's method. The results showed that P. cereifera flower was monoecious, had morphological character that supported nocturnal pollination. Stigma and anthers spatially separated, but there was no temporal separation of stigma receptivity and anther dehiscence. Based on the flower biology, the pollen ornamentation (reticulate type), and the Out-Crossing Index (OCI=4), the breeding system was outcrossing but partially self-compatible, required pollinators (zoophily)

Nocturnal and diurnal pollination in Copaifera coriacea, a dominant species in sand dunes of the Middle São Francisco River Basin, Northeastern Brazil

Background and aims – Copaifera coriacea, a species in the resin-producing clade Detarioideae (Leguminosae), is an endemic and abundant species found in sand dunes in Brazilian Caatinga domain vegetation – a Quaternary paleodesert. We investigated floral traits and aspects of pollination biology, focusing on the pollination system of C. coriacea. Material and methods – Anthesis duration, stigma receptivity, pollen viability, nectar concentration, and the presence of osmophores and pigments reflecting UV light were assessed. Floral visitors were classified as potential pollinators, occasional pollinators or thieves, based on the time and foraging behaviour and resource collected. Pollination effectiveness were assessed for potential pollinators by the detection of pollen tubes on the stigma or stylar canal by epifluorescence microscopy.Key results – The species has white and small flowers, with anthesis beginning in the dark (ca 00:30) and the flowers are completely opened approximately 3 h later, when a sweet odour is perceptible. The onset of stigma receptivity and pollen grain viability occurs only after the completion of flower opening, and a concentrated nectar is available during the day. The presence of pollen tubes confirmed the efficiency of the main insects in the transfer of pollen. Conclusion – Our result demonstrates that C. coriacea has a generalist pollination system mediated mainly by two distinct guilds of insect pollinators: moths (nocturnal, searching for nectar) and bees (diurnal, pollen collectors). This finding can provide more information about diversification in the genus Copaifera.

Hybridization of Castor Bean (Ricinus communis L.) in Morelos, México

Objective: To determine the stigma receptivity and the pollen viability in order to make manual crosses and obtain viable progeny in castor bean (Ricinus communis L.).Design/Methodology/Approach: Pollen viability tests were made on breeding materials by staining with acetocarmine solution. In elite materials, the receptivity of the stigma was evaluated with hydrogen peroxide. From the inflorescences, the male ones were removed and the female ones were preserved, which were covered with a glassine bag. After six days, they were checked and when they were considered receptive, manual pollinations were carried out between viable pollen materials and receptive stigma. The pollen of the male parent was impregnated in the stigmas and the inflorescence was covered again.Results: The breeding materials exhibited viable pollen since they were stained red. Whereas, the application of hydrogen peroxide to the stigmas of the elite materials showed bubbling, indicative that they were receptive. In 2014, 400 inflorescences were pollinated with 8 flowers on average and a fruit pollinated percentage of 61.21. In 2015, 245 inflorescences with 12 flowers on average and 61.24% of fruit were pollinated.Study Limitations/Implications: Temperature and relative humidity were fundamental factors for the success of castor bean fertilization.Findings/Conclusions: The elite castor bean materials presented receptive stigmas and the improved viable pollen materials. Manual crosses produced fruits and seeds. The fruits pollinated were 61%.

Pollination Studies on Both Floret and Capitulum Levels in an Oil Seed Crop,Guizotia abyssinica(L.f.) Cass.

Niger,Guizotia abyssinica(L.f.), is an important oilseed crop widely grown in Ethiopia and India, but poor pollination is one of the major constraints in achieving the yield potential of the crop. Our aim was to understand better the pollination biology and role of flower insect visitors in reproduction success. Results indicated that full anthesis occured in the morning between 06.00 and 08.00 h and pollen dehiscence eight to eleven hours after anthesis. Stigma receptivity commenced nine hours after anthesis and lasted for the next 24 h. A total of eighteen insect species representing six families visited Niger flowers, and among these,Apis floreaandA. ceranawere dominant. The flowers were self-incompatible as there was no seed set upon the selfing of floret and selfing of capitulum. The maximum seed set (78.33±0.14%) was noticed when flowers were allowed for open pollination and the lowest was recorded when the whole plant was caged to exclude pollinator visits (0.33±0.67). The time spent byA. ceranaandA. floreawas 1.35±0.48 and 1.83±0.12 seconds per floret, respectively and 9.63±0.69 and 14.9±0.94 seconds per capitulum, respectively.A. ceranaandA. floreawere found to be more efficient pollinators ofG. abyssinica.Introducing bee colonies might greatly improve the yield, and it is also important to conserve bees in the vicinity ofG. abissynicafields during the flowering period. Hence, introducing bee colonies might greatly improve the yield of Niger.

Pollination Biology of Lespedeza davurica

Background: In order to reveal the pollination biological characteristics of Lespedeza davurica, wild L.davurica from eight regions of Shanxi Province was used as test materials to study their floral dynamic, pollen storage and other aspects.Methods: During 2019, the flowering dynamics of wild L. davurica collected from eight regions of Shanxi Province were observed by selecting the better-grown L.davurica. Freshly bloomed flowers were picked, and their pollen was set up for two treatments, dry and undried, for pollen storage experiments. Pollen viability was determined by the TTC (expand for first instance) and MTT (expand for first instance) methods and stigma receptivity was determined by the hydrogen peroxide-benzidine method.Result: The results showed us the following points: the flowers of L. davurica were pale yellow, large and fragrant; it usually opens from the base to the top with distinctly asymmetrical petals; it opens during the day and closes at night; the number of flowers reached its peak between 12:00 and 14:00. After measuring the pollen viability of L. davurica, we found that dry storage at -20°C was the most effective treatment. And with the increase of temperature and decrease of humidity, the pollen viability and stigma receptivity of L. davurica increased continuously and the highest viability value occurs between 12:00 and14:00.

Reproductive and pollination biology of the Critically Endangered endemic Campanula vardariana in Western Anatolia (Turkey)

Background and aims – Campanula vardariana (Campanulaceae) is a critically endangered endemic chasmophyte with a single population situated in the west of Turkey. Very little is known about the reproductive biology of C. vardariana and more information is needed to develop a sound conservation strategy for this endemic species.Material and methods – Floral traits such as flower morphology, nectar, and sugar concentration, as well as pollen viability and stigma receptivity were measured in different floral phases. We observed insect visitations to the flowers and identified pollinators. Additionally, we investigated the effect of cross and self-pollination on fruit and seed production.Key results – The flowers of C. vardariana are protandrous. The length of the styles, which were 8.74 mm during the pollen loading phase, reached 11.35 mm during the pollen presentation phase. The visitor observations made on the C. vardariana flowers revealed 11 visitor species from 5 families: 5 Halictidae, 3 Apidae, and one species each from Megachilidae, Colletidae, and Bombyliidae. Lasioglossum spp. touched the anthers and stigma using several parts of their bodies and were significant pollinators of C. vardariana. Under natural conditions, the mean number of seeds per fruit was around 60 after cross pollination, while no fruits were formed when pollinators were excluded.Conclusion – Campanula vardariana is entirely dependent on pollinators for its reproductive success, and bees, especially Halictidae and to a lesser extent Apidae, play an important role. Campanula vardariana is restricted to cracks in calcareous rocks and its population is threatened by goat overgrazing and mining activities (quarry formation). Since seed production is abundant in this population, anthropogenic activities currently form the biggest threat to its existence.

Pollinating potential of bee floral visitors of Spondias mombin (Anacardiaceae) cultivated in northeastern Brazil

To better understand the relationship between Spondias mombin (Anacardiaceae) with its floral visitors, we investigated stigma receptivity and flowering pattern, as well as the abundance, frequency and behavior of bees visiting its flowers, aiming to discuss their potential as pollinator of this plant species. We studied S. mombin in an orchard in Northeastern Brazil. Stigma receptivity coincided with the time bees were foraging, mainly for pollen. According to the bee behavior on flowers, their visiting hour, abundance, and frequency in the studied area, we concluded that Apis mellifera (Linnaeus), Trigona spinipes (Fabricius), Xylocopa grisescens (Lepeletier) and Augochloropsis sp. are potential pollinators of S. mombin. Also, A. mellifera and T. spinipes were the most abundant species in the area and collected floral resources with greater frequency, contributing more significantly to pollination. Due to the overwhelmingly presence of these two bee species in NE Brazil, we conclude they are the main potential pollinators of S. mombin in the region.