Flavonoid compounds related to seed coat color of wheat

In red wheat, reddish-brown pigments accumulate in testa of mature seeds. Half-cut wheat seeds were immersed in p-dimethylaminocinnamaldehyde (DMACA) reagent that stains flavanol structures blue. Testa of 10–40 days after flowering (DAF) in red wheat (“Norin 61” and “Satonosora”) seeds were stained blue and the reagent color changed to blue with 10–25 DAF seeds. No blue staining was observed in white wheat (“Tamaizumi”) seeds during maturation. “Norin 61” seed coats at 10 DAF contained dihydroquercetin, dihydromyricetin, (+)-catechin, procyanidin B3, and prodelphinidin B3, which were identified by HPLC-diode array detector and LC-MS/MS analyses. These five components began accumulating 7 DAF, reached maxima at 10 or 15 DAF, and then decreased in red wheat seeds, but were not detected in white wheat seeds. These results suggest that flavanol and proanthocyanidins are possible precursors of the reddish-brown pigments of red wheat seeds, and are converted to insoluble compounds as the seeds mature.     

FLORAL COLOR CHANGE IN LUPINUS ARGENTEUS (FABACEAE): WHY SHOULD PLANTS ADVERTISE THE LOCATION OF UNREWARDING FLOWERS TO POLLINATORS?

I examined the adaptive significance of two floral traits in the perennial herb, Lupinus argenteus: 1) the retention of corollas on “spent” flowers, i.e., flowers containing inviable pollen, unreceptive stigmas, and negligible pollinator rewards and 2) a change in corolla color of retained “spent” flowers, which is restricted to a spot on the banner petal. At anthesis, this spot is yellow, and approximately four days later, it changes to purple. After the change, purple flowers remain on plants an additional 5–7 days before corolla abscission occurs; purple flowers were avoided by pollinators, presumably because they contained less pollen (rewards) than yellow ones. I experimentally tested the hypothesis that purple flowers contribute to the floral display of the plant by removing varying numbers of spent flowers and assessing the effect on pollination visitation. Pollinators preferentially approached and foraged on plants with greater numbers of flowers per inflorescence; they did not discriminate between yellow (rewarding) and purple (nonrewarding) flowers at interplant distances greater than 0.4 meters but would preferentially forage on plants with more total flowers, even if these individuals contained fewer rewarding flowers. Thus, spent flowers increased the overall attractiveness of plants to pollinators. In theory, color change may benefit plants in two ways. First, by directing pollinators to rewarding flowers, the change may increase pollinator foraging efficiency, with the result that pollinators visit more flowers before leaving plants (pollinator-tenure mechanism). Second, by directing pollinators to receptive flowers, the color change may prevent incoming pollen from being wasted on unreceptive stigmas and may prevent collection of inviable pollen (pollination-efficiency mechanism). I tested the pollinator-tenure mechanism experimentally by removing pollen from yellow flowers, thereby reducing the reliability of the color-reward signal. Pollinators visited fewer total flowers on experimental plants than on controls, resulting in reduced seed production in one year.     

Differential Sensitivity of Macrocarpa and Microcarpa Types of Chickpea （Cicer arietinum L.） to Water Stress： Association of Contrasting Stress Response with Oxidative Injury

Chickpea (Cicer arietinum L.) is particularly sensitive to water stress at its reproductive phase and, under conditions of water stress, will abort flowers and pods, thus reducing yield potential. There are two types of chickpea: (i) Macrocarpa (“Kabuli”), which has large, rams head‐shaped, light brown seeds; and (ii) Microcarpa (“Desi”), which has small, angular and dark‐brown seeds. Relatively speaking, “Kabuli” has been reported to be more sensitive to water stress than “Desi”. The underlying mechanisms associated with contrasting sensitivity to water stress at the metabolic level are not well understood. We hypothesized that one of the reasons for contrasting water stress sensitivity in the two types of chickpea may be a variation in oxidative injury. In the present study, plants of both types were water stressed at the reproductive stage for 14 d. As a result of the stress, the “Kabuli” type exhibited an 80% reduction in seed yield over control compared with a 64% reduction observed for the “Desi” type. The decrease in leaf water potential (Ψ_w) was faster in the “Kabuli” compared with the “Desi” type. At the end of the water stress period, Ψ_w was reduced to ?2.9 and ?3.1 MPa in the “Desi” and “Kabuli” types, respectively, without any significant difference between them. On the last day of stress, “Kabuli” experienced 20% more membrane injury than “Desi”. The chlorophyll content and photosynthetic rate were significantly greater in “Desi” compared with “Kabuli”. The malondialdehyde and H₂O₂ content were markedly higher at the end of the water stress in “Kabuli” compared with “Desi”, indicating greater oxidative stress in the former. Levels of anti‐oxidants, such as ascorbic acid and glutathione, were significantly higher in “Desi” than “Kabuli”. Superoxide dismutase and catalase activity did not differ significantly between the two types of chickpea, whereas on the 10th day, the activities of ascorbate peroxidase, dehydroascorbate reductase, and glutathione reductase were higher in “Desi”. These findings indicate that the greater stress tolerance in the “Desi” type may be ascribed to its superior ability to maintain better water status, which results in less oxidative damage. In addition, laboratory studies conducted by subjecting both types of chickpea to similar levels of polyethylene glycol‐induced water stress and to 10 μ.mol/L abscisic acid indicated a greater capacity of the “Desi” type to deal with oxidative stress than the “Kabuli” type. (Managing editor: Ping He)     

Foraging and pollination behaviour of Xylocopa calens Lepeletier (Hymenoptera: Apidae) on Phaseolus coccineus L. (Fabaceae) flowers at Yaounde (Cameroon)

To evaluate impact of carpenter bee, Xylocopa calens, on pod and seed set of Phaseolus coccineus, its foraging and pollinating activities were studied in Yaounde, for two seasons (May–July 2008 and April–June 2009). Observations were made on 40 inflorescences per treatment. The treatments included unlimited floral access by all visitors, bagged flowers to deny all visits, and limited visits by X. calens only. In addition, all flower visitors were recorded. The carpenter bee's seasonal rhythm of activity, its foraging behavior on flowers, its pollination efficiency, the fructification rate and the number of seeds per pod were recorded. Individuals from 16 species of insects were recorded visiting flowers of P. coccineus in the 2 years. Xylocopa calens was the most frequent, followed by Chalicodoma cincta cincta and Apis mellifera. Apart from bees, wasps were also recorded as likely predators. Xylocopa calens mainly foraged for nectar resources. The mean foraging speed was 9.62 flowers/min. Flowers visited by X. calens had higher fruiting rate compared with others, while those bagged had the lowest. In addition, seed formation was higher in X. calens‐visited flowers compared with all others. The results show that this crop experiences pollination deficit even under normal circumstances, considering that flowers visited by X. calens had higher yields compared with those under unlimited access by all visitors. The fruiting rate, the number of seeds/pod and the percentage of normal seeds of unprotected inflorescences were significantly higher than those of inflorescences protected from insects. X. calens foraging resulted in a significant increment of the fruiting rate by 25.80%, as well as the number of seeds/pod by 14.97% and the percentage of normal seeds by 27.75% in 2008 and 18.39% in 2009. Conservation of X. calens nests close to P. coccineus fields could be recommended to improve pod and seed production in the region.     

Reproductive biology ofCistus ladanifer (Cistaceae)

The phenology, major floral characteristics, fruiting levels, and breeding system ofCistus ladanifer L. (Cistaceae), a common western Mediterranean shrub species, were studied in a southern Spanish population. The white, large (64 mm in diameter) flowers of this shrub appear during spring (March–May) and produce abundant pollen and nectar. In the year of study, flowers lasted up to three days, during which they were visited by a diverse array of insects including beetles, flies, and bees. Hand-pollinations revealed that flowers do not set any seed unless cross pollen is applied to the stigma. Microscopical observations indicate that self pollen tubes grow down the stigma but invariably fail to induce fruit maturation. At the plant level, all estimates of fecundity investigated (number of seeds per capsule, proportion of ovules developing into seed, and proportion of flowers setting fruit) were highly dependent on nearest neighbour distance, with isolated plants setting as little as 0% fruit. In contrast, plants within a clump often transformed into fruit as much as 90% of the flowers. At the population level, seed output was estimated to range between 3,000 and 270,000 seeds per plant during 1991.     

Fruit choice by red howler monkeys (Alouatta seniculus) in a tropical rain forest

This paper presents and discusses aspects of fruit selectivity by red howler monkeys (Alouatta seniculus) in relation with morphological characteristics of fruits. These data are used to provide an answer to the following questions: which are the fruit characteristics that lead fruit choice of howler monkeys and to what extent fruit characteristics play a role in seed dispersal by monkeys? The frugivorous diet of a troop of red howler monkeys was determined during a 2-year field study in French Guiana. The selection of fruit by howler monkeys was analyzed in relation to the fruit availability. Results showed that, although consumption followed availability, fruit species could be classified in three categories according to their selection ratio (percentage of consumption/percentage of abundance) as “high ranking,” “middle ranking,” and “low ranking” species. Also, the 97 species of fruit eaten by the monkeys were grouped according to the morphological characteristics thought to influence the monkeys' choice. This showed that howler monkeys consumed essentially fruits with juicy pulp, bright color, and a small number of well-protected seeds. Most of high ranking species had medium-sized fruits with yellow color, and low ranking species often had small fruits. However, howler monkeys are associated with the dispersal of seeds from fruit with a hard and indehiscent pericarp and/or large seeds, like those of the Sapotaceae family. Consequently, they can be considered as “specialized” frugivores for this fruit syndrome. © l996 Wiley-Liss, Inc.     

Dichilanthe, an unusual Asiatic Rubiaceae with "Lonicera flowers" and "dipterocarp fruits"

Dichilanthe, a disjunctly distributed, arborescent Southeast Asiatic genus (D. zeylanica: Sri Lanka; D. borneensis: West Borneo) with collar-like, persistent stipules, has strongly zygomorphic, ornithophilous flowers which show secondary pollen presentation. The curved corolla is two-lipped. The upper lip consists of 2, and the lower lip of 3 fused corolla lobes. The calyx, too, is zygomorphic. The curved, exserted style ends in a swollen “stylar head' which apically bears two small stigmatic (receptive) areas in a zygomorphic arrangement. The flowers are borne in compact, terminal heads, held together by enlarged stipules of a bract-pair immediately below the inflorescence. The dispersal units (diaspores) mimic dipterocarp fruits. They consist of a persistent, wing-like pair of bracts whose±cuplike stipules enclose the fruits. The diaspores break off at the node immediately below the bract-pair, where there is a distinct abscission zone. Initial on”primary“dispersal by wind may be followed by facultative”secondary“dispersal by floating in water.”Pith tissue“produced by each fruit of the diaspore, and the air spaces contained therein, are likely to be adaptations to floating. This”pith tissue“, a loose, parenchymatic,± irregularly arranged area of the fruit wall which partially disintegrates during fruit maturation, represents a modified portion of the endocarp; the remainder of the endocarp is”normal“sclerenchymatic tissue coating the two locules. The initial stages of this endocarp differentiation are already observable in early developmental stages, i.e., in ovaries of flower buds and open flowers. The bicarpellate ovaries contain a solitary, anatropous pendulous ovule per locule. Viable seeds have large embryos and only c. 5–6 layers of oily endosperm; their exotesta cells have delicate, ring-like thickenings. In developing fruits of individual inflorescences, a high frequency of seed abortion was noted. Not uncommonly, there is only a single viable seed per dispersal unit, i.e., only a solitary seedling emerging from a diaspore. Germination of the seeds is cryptocotylar. The pollen of D. zeylanica is suboblate and 5- or 6-colpate (with the colpi being rather short); the exine is finely reticulate. In spite of several of its character states being unusual and aberrant, the tribal position of Dichilanthe in the Guettardeae is not questioned, although it is concluded that the genus occupies a rather isolated position in the tribe.     

Fruit and seed ecology of wild robusta coffee (Coffea canephora Froehner) in Kibale National Park, Uganda

Coffee fruit production, frugivorous activities and seed longevity were investigated during two seasons. The average densities of fruiting coffee trees during the first sampling period ranged from four to seven per 25 m² and during the second sampling period, four fruiting trees per 25 m² were estimated. Fruiting coffee trees were significantly less than the non-fruiting trees ( P < 0.05, t -test). Periods of maximum coffee fruit fall coincided with those of lowest rainfall. Coffee fruit yield per tree from ground collections was 7–40 m⁻² in 1992 and 16–38 m⁻² in 1993/1994. Split coffee berries ranged between 71.7% and 83.6% of all fruits collected from the forest floor in the 1993/94 sampling period. Coffee seeds collected from the forest floor were mostly undamaged. Black and white colobus and redtail monkeys were observed to feed on ripe coffee fruits but did not crush the seeds. Coffee seed viability declined rapidly during storage. Seeds left on the forest floor survived longest, those stored under laboratory conditions lost viability fastest, and those in cold storage showed intermediate longevity.     

Seed yield,head characteristics and oil content in sunflower varieties as influenced by seeds from single and multiple headed plants under humid tropical conditions

Field trials were conducted during 2004 and 2005 to determine the effect of sowing seeds from plants with multiple heads and seeds from single headed plants of sunflower on seed yield, head characteristics and oil content of three widely grown open pollinated varieties (Funtua, Record and Isaanka) in the humid forest—savanna transition zone which is outside the current growing areas with a view to improving stability and sunflower productivity in this region. Seeds from multiple headed plants produced plants that flowered and matured 2–3 days later than plants from single headed plants. Apart from days to flowering in 2004, number of days to maturity and plant height were affected independently by variety and seed source factors. However, the seeds from single headed plants produced plants that recorded significantly (P < 0.01) higher head weight, head diameter, achene weight and number per head than plants from seeds of plants with multiple heads. Seed source had little effect on sunflower seed yield and oil content. However, Funtua produced significantly (P < 0.05) high seed yield (1956.0 kg ha^?1 ± 76.06) when seeds from plants with multiple heads were sown, while Isaanka recorded comparatively high seed yield from seeds of plants from either multiple (1221.0 kg ha^?1 ± 165.90) or single heads (1388.0 kg ha^?1 ± 135.84) and Record (1201.0 kg ha^?1 ± 96.97) when seeds from single headed plants were sown. Therefore, it is recommended that prospective sunflower growers who wish to cultivate Isaanka, can sow seeds from either the multiple or single head and preferably the multiple head for Funtua, and single head for Record.     

荒漠植物准噶尔无叶豆结实、结籽格局及其生态适应意义

连续2a采用野外记录的方式对荒漠植物准噶尔无叶豆的结实、结籽格局进行了比较研究。结果表明:植株内花序生成格局表现为不同大小的花序在总花序中的比重与其结实率存在显著正相关,其中含有中等花数目的花序所占的比重及其结实率均最高,此种分布格局能够最大程度的保证繁殖成功;果序内果实生成格局表现为单花着生位置(从近柄端算起)与其结实量占总结实量的比例成线性负相关,花序基部的结实比例最高,顶部结实比例近为0;荚果内种子生成格局表现为:中间位置的胚珠败育率最低。另外,年际间荚果内仅有(1.08±0.03)粒和(1.07±0.03)粒种子能够完全成熟,此种结籽格局是准噶尔无叶豆保证后代质量的最佳策略。     

An updated classification for the hyper-diverse genus Corydalis (Papaveraceae: Fumarioideae) based on phylogenomic and morphological evidence

The genus Corydalis, with ca. 530 species, has long been considered taxonomically challenging because of its great variability. Previous molecular analyses, based on a few molecular markers and incomplete taxonomic sampling, were clearly inadequate to delimit sections and subgenera. We have performed phylogenetic analyses of Corydalis and related taxa, using 65 shared protein-coding plastid genes from 313 accessions (including 280 samples of ca. 226 species of Corydalis) and 152 universal low-copy nuclear genes from 296 accessions (including 271 samples of Corydalis) covering all 42 previously recognized sections and five independent “series”. Phylogenetic trees were inferred using Bayesian Inference and Maximum Likelihood. Eight selected morphological characters were estimated using ancestral state reconstructions. Results include: (i) of the three subgenera of Corydalis, two are fully supported by both the plastid and nuclear data; the third, subg. Cremnocapnos, is weakly supported by plastid DNA only, whereas in the nuclear data the two included sections form successive outgroups to the rest of the genus; (ii) among all 42 sections and five “series”, 25 sections and one “series” are resolved as monophyletic in both data sets; (iii) the common ancestor of Corydalis is likely to be a perennial plant with a taproot, yellow flowers with a short saccate spur, linear fruits with recurved fruiting pedicels, and seeds with elaiosomes; (iv) we provide a new classification of Corydalis with four subgenera (of which subg. Bipapillatae is here newly described), 39 sections, 16 of which are consistent with the previous classification, 16 sections have been recircumscribed, one section has been reinstated and six new sections are established. Characters associated with lifespan, underground structures, floral spur, fruit and elaiosomes are important for the recognition of subgenera and sections. These new phylogenetic analyses combined with ancestral character reconstructions uncovered previously unrecognized relationships, and greatly improved our understanding of the evolution of the genus.     

明亮熊蜂和意大利蜜蜂为温室草莓的授粉行为比较观察

蜜蜂和熊蜂都是理想的授粉昆虫,但熊蜂比蜜蜂更适合为温室果菜授粉,主要由于熊蜂和蜜蜂授粉时的活动方式不同。作者对明亮熊蜂和意大利蜜蜂为日光温室草莓授粉时的行为和活动方式进行了比较研究。结果表明,明亮熊蜂和意大利蜜蜂的授粉行为相似,但活动方式不同。明亮熊蜂开始访花的时间（8:00～8:05）比意大利蜜蜂（9:25～9:40）早,停止访花的时间（15:55～16:05）却比意大利蜜蜂（15:20～15:30）晚;开始访花的温度（12～13℃）也比意大利蜜蜂（>15℃）低,意大利蜜蜂在早晨和阴天不访花。明亮熊蜂个体的日活动时间271.43±4.48 s,明显比意大利蜜蜂个体的日活动时间180.00±2.64 s长,差异显著;而采集时间为105.71±1.16 s,显著长于意大利蜜蜂的76.43±3.83 s。明亮熊蜂每分钟平均访花数为8.44±0.44,极显著高于意大利蜜蜂每分钟的平均访花数2.38±0.15;明亮熊蜂访花间隔为3.81±0.42 s,极显著短于意大利蜜蜂的6.0±0.48 s。明亮熊蜂访花具有选择性,每天访早期花平均为55%,意大利蜜蜂则无选择性,每天访早期花平均为34%,二者差异显著;在9:00～12:00明亮熊蜂访早期花平均为75%,意大利蜜蜂访早期花则仅为31%。熊蜂在花间和花簇间活动频繁,平均移动距离为5.2 m;而意大利蜜蜂很少在花簇间移动,平均移动距离只有1.1 m。据此得出明亮熊蜂为日光温室草莓授粉的活动特性优越于意大利蜜蜂,从而产生更高的授粉效益。     

Pollination of Kadsura longipedunculata (Schisandraceae), a monoecious basal angiosperm, by female, pollen-eating Megommata sp. (Cecidomyiidae: Diptera) in China

The plants of Kadsura longipedunculata (Schisandraceae) are monoecious and possess either red or yellow male flowers (the androecium), with yellow tepals, and yellow female flowers. All flower types simultaneously produce heat and floral odours (dominated by methyl butyrate) throughout a 4–5-h nocturnal period. The flowers are pollinated only by female, pollen-eating Megommata sp. (Cecidomyiidae). Pollen is the only reward, and female flowers use the same attractants as male flowers but offer no food (pollination by deceit). Open pollinated flowers in nature varied in fruit set from 8 to 92%. Megommata (subfamily Cecidomyiinae, supertribe Cecidomyiidi), consists of six described species, which feed on Coccoidea (scale insects) and are distributed worldwide.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 523–536.     

Distribution of bollworm,Helicoverpa zea (Boddie), injured reproductive structures on genetically engineered Bacillus thuringiensis var. kurstaki Berliner cotton

Bollworm, Helicoverpa zea (Boddie), larvae are commonly observed feeding in genetically engineered Bollgard cotton. Although no information is currently available characterizing the levels of injury bollworms cause, aproximately 25% of the Bollgard acreage in the United States receives at least one insecticide application annually targeting bollworm populations. Studies were conducted to determine the levels of fruiting form injury that can occur from bollworm larvae feeding on white flowers of two types of genetically engineered cotton. The two types of genetically engineered cotton included the original Bollgard that produces one protein (Cry1Ac) from Bacillus thuringiensis variety kurstaki Berliner and Bollgard II that produces two proteins (Cry1Ac + Cry2Ab) from B. thuringiensis kurstaki. In one study, individual larvae (24 +/- 6 h old) were placed in first position white flowers of Deltapine 5415 (non-Bollgard) and Deltapine NuCOTN 33B (Bollgard). Larval infestations were made on 50 plants for each of 5 d during 2000 and 2001. Each plant was visually examined at 3 d and every 2 d thereafter, until larvae were no longer recovered. Larvae injured a total of 46.6 fruiting forms per 50 plants on non-Bollgard cotton, compared with only 18.9 fruiting forms per 50 plants on Bollgard cotton. Mean larval injury per insect was 4.3 fruiting forms on non-Bollgard cotton compared with 2.7 fruiting forms on Bollgard cotton. In a second study, individual larvae (24 +/- 6 h old) were placed in first position white flowers of Deltapine 50 (non-Bollgard), Deltapine 50B (Bollgard), and an experimental Bollgard II line. Larval infestations were made on 10 plants per day for each of six consecutive days during 2001. Larvae injured a total of 25.0 fruiting forms per 10 plants on non-Bollgard, 11.5 on Bollgard, and 6.4 on Bollgard II cottons. Mean larval injury per insect was 6.6 fruiting forms on non-Bollgard, 3.5 on Bollgard, and 0.8 on Bollgard II cottons. These data indicate that supplemental insecticide applications may be necessary to prevent yield losses on Bollgard cotton. In contrast, injury to Bollgard II cotton was minimal and may not require additional insecticide applications for bollworms.     

ECOLOGICAL CORRELATES OF REPRODUCTIVE TRAITS OF MEXICAN RAIN FOREST TREES

Sexual systems of 139 tree species from a tropical rain forest at Los Tuxtlas, Mexico were investigated to: 1) estimate the relative proportions of hermaphroditic, monoecious, and dioecious species; 2) describe flowers, fruits, and seeds in terms of size and weight; 3) describe flowering and fruiting phenology; and 4) correlate sexuality to pollination and dispersal syndromes, and the successional status occupied in the forest. Hermaphroditism occurred in 63% of the species, monoecism in 9%, and dioecy in 27%. Nondioecious species had larger flowers, but dioecious species had more seeds per fruit. The dioecious condition was associated with small flowers pollinated with unspecialized insects and fleshy fruits dispersed by animals at both species and generic levels. Reproductive traits were more correlated among nondioecious species than dioecious species. Pioneer species had more seeds per fruit, and longer flowering and fruiting periods, but persistent species produced heavier seeds and fruits. Flower and fruit morphological traits, sexual systems, and tree guilds are related in a comprehensive way, and a flow model based on data from this study is presented.     

Temporal patterns of seed set and decelerating fitness returns on female allocation in Zigadenus paniculatus (Liliaceae), an andromonoecious lily

I describe temporal patterns of seed production in the andromonoecious lily Zigadenus particulatus. Fruit set per flower and seed set per fruit declined through time within plants. Hand pollination experiments showed that this was not due to increasing pollen limitation. Nutrient supplementation had little effect on seed output, but leaf clipping reduced seed production, especially in late-blooming flowers, and removal of early-blooming flowers increased seed set by later flowers. Thus, the temporal pattern of seed output was due to declining availability of photosynthates. Plants with larger bulbs produced larger inflorescences, a greater proportion of hermaphrodite flowers, more fruits per hermaphrodite flower, and more seeds per fruit, but lost a greater fraction of their initial bulb mass as a consequence of fruiting. After controlling for the effects of bulb mass, plants with larger inflorescences produced a greater proportion of male flowers, and plants with more hermaphrodite flowers produced fewer fruits per hermaphrodite flower and fewer seeds per fruit. Thus, the female fitness gain curve was decelerating. The temporal decline in seed output provides a partial explanation for the parallel decline in allocation to pistils. However, a complete explanation for the pattern of gamete packaging requires an understanding of factors controlling male, as well as female, fitness.     

Establishment of a porcine corneal endothelial organ culture model for research purposes

Human corneas usually are not available for research, as they are used for transplantation only. At the same time, scientific studies on cultured human endothelial cells can produce misleading results due to inevitable dedifferentiation. Therefore, an organ-culture model of porcine corneas—displaying endothelial cell death rates comparable to those of cultured human corneas—would be very desirable. Fresh pig eyes were prepared under sterile conditions to obtain corneoscleral buttons, corneal buttons and so called “split corneal buttons” (new preparation method) and cultivated for 15 days. Morphology of the endothelial cell layer was observed by light microscopy on day 1, 8 and 15. On day 15 staining with trypan blue and alizarin red S was performed. Photographs were evaluated in a randomized, blinded manner. Here, the morphology of the corneal endothelium and the number of endothelial cells per mm² were analyzed. After 15 days of cultivation the endothelial cell layer was maintained only in corneal buttons and split corneal buttons. Alizarin red S stained areas and the existence of polymorphisms like rosette figures and reformation figures were significantly less frequent in split corneal buttons than in corneal buttons. Loss of endothelial cells was significantly greater in corneal buttons [575 ± 25/250 cells/mm² (median ± 25%/75%-quantile); 14.8%] than in split corneal buttons [417 ± 138/179 cells/mm² (median ± 25%/75%-quantile); 10.2%]. The new preparation method of split corneal buttons allows the cultivation of porcine corneas for 2 weeks with cell death rates comparable to those of the corresponding human tissue in cornea banks without the need to add de-swelling additives to the media. This is therefore a simple and highly reliable method model to be applied in intervention studies on corneal endothelial cells in their natural compound.     

Floral biology and pollination in Cucumis melo L., a tropical andromonoecious cucurbit

We studied floral biology and the role of flower visitors in fruit set of muskmelon (Cucumis melo L.). Muskmelon produced Staminate (hereafter ‘S’) and Hermaphrodite (hereafter ‘H’) flowers with a ratio of 18:1. Flowers opened around 40 days after planting and flowering continued for another 40 days. Longevity of both types of flowers was one day. Anthesis in S flowers was earlier (0545–0700 h) than that of H flowers (0700–0830 h). Anther dehiscence occurred 10–15 min after anthesis in both the flowers. The number of pollen grains in H flowers was significantly lower (2715 ± 143) than S flowers (4968 ± 398). Pollen viability and stigma receptivity was maximum between 1600 and 1800 h. The pollen tube of pollen grains from H flowers grew very slowly and never reached the ovary. There were two peaks in nectar production in a day (1000–1200 h and 1400–1800 h). Sixteen species of insects belonging to Hymenoptera (81.25%), Diptera (12.50%) and Lepidoptera (6.5%) visited muskmelon flowers. Major visitors were honeybees, Apis cerana F. and A. florea F. and both were efficient pollinators. Diversity and abundance of flower visitors positively correlated with floral abundance. In pollination exclusion experiments, no fruit set was observed in bagged, self-pollinated and the flowers artificially crossed only with other H pollen. But, those flowers hand pollinated with pollen from S flowers and ones that were allowed for open pollination set maximum fruits. The crop needs a minimum of 8–10 bee visits per flower to achieve the same level of pollination efficiency provided with natural/unrestrained visits.     

OIL FLOWERS AND OIL BEES: FURTHER EVIDENCE FOR POLLINATOR ADAPTATION

We examined foreleg length and body size variation in two species of oil-collecting bees (Rediviva; Melittidae) in southern Africa. Oil-collecting bees harvest oil from host flowers by rubbing their forelegs against oil-secreting trichomes. Significant differences in foreleg length occur among populations of both species. Rediviva “pallidula” populations vary significantly in mean foreleg length (11.34 ± 0.42 mm to 12.67 ± 0.36 mm), but not in body length (10.59 ± 0.74 to 10.80 ± 0.64), and foreleg length and body size are not significantly correlated. Instead, foreleg variation appears to be a function of host plant spur length. Ninety-two percent of the variance in foreleg length of R. “pallidula” is explained by mean Diascia spur length. Rediviva rufocincta populations vary significantly in mean foreleg length (10.12 ± 0.70 mm to 12.34 ± 0.68 mm) and in body length (9.03 ± 0.26 mm to 10.56 ± 0.24 mm). Foreleg length scales allometrically with body size in this species as 90.5% of the variance in foreleg length can be explained as a function of body length. Body size appears to be constrained by the morphology of the oil-secreting host plant. Both bees collect floral oil with specially modified setae on the tarsi of their forelegs. The length of the disti- + mediotarsus (refered to here as “tarsus”) in relation to the entire foreleg is shorter in R. rufocincta and does not increase as rapidly with increasing foreleg length as for R. “pallidula.” These differences in variation can be attributed to differences in position of oil within the flowers of the respective host plants. Rediviva “pallidula” collects oil from Diascia species that have the oil deeply situated in narrow floral spurs of varying length, while R. rufocincta collects oil from the broadly saccate flowers of Bowkeria verticillata and B. citrina.     

Interaction Effects of Seed Mass and Temperature on Germination in Australian Species of Frankenia (Frankeniaceae)

The seed size and number theories have been proposed to explain the advantages of having many small versus a few large seeds in plants. In particular, seed germination is predicted to be shaped by temperature, and may differ for small and large seeds. In this study, we experimentally test germination at different temperatures in 12 species of arid zone plants in the genus Frankenia L. that differ in seed mass. Seed mass was categorized as “smaller-seeded species” versus “larger-seeded species” for analysis (six species per category). Many of these species co-occur geographically and hence experience similar abiotic conditions (unpredictable rainfall, extremes in temperature, poor soil conditions). The results demonstrated differences in germination as a result of the temperature*seed mass(species) interaction effect. There were significant differences in germination rates across seed mass categories during the first eight days of germination. Germination rates were higher in the larger-seeded species than the smaller-seeded species. Smaller-seeded species had lower germination success but had higher germination rates at lower temperatures, and had a more stringent temperature as a germination cue. These findings are discussed in the context of life-history strategies in arid zone plants.