The International Journal of Plant Reproductive Biology
(Indexed by CABI)
ISSN Print : 0975-4296; ISSN Online : 2249-7390
   
Volume-1, Number-1, January 2009

Mechanism of Self Pollination in Cymbidium sinense (Jacks. ex Ander). Willd. (Orchidaceae)

S.K. Chaturvedi
Department of Botany, Nagaland University, H.Qs. – Lumami, Mokokchung, 798601, Nagaland, India

ABSTRACT

Members of family orchidaceae are adapted for the biotic pollination through insects and birds in possessing a highly specialized floral morphology. A typical orchid flower exhibiting a labellum as a landing platform for the visitor / pollinators and the reduction of the stamen and pistil to a single structure, the column, is certainly the apex of floral adaptation to insects as pollinating agents. The function of pollen deposition is characterized precisely in the median plane opposite the labellum. The pollinarium of orchids consists of viscidium, stipe and pollinium. .Being attached at the apical portion of the column, pollinarium is easily removed and deposited by the pollinators. At the sub- apical portion of the column lays the receptive surface of the stigma called rostellum. For the completion of pollination process the pollinarium has to be inserted into the rostellum either biotically or abiotically. The biotic pollination in orchids is well known but the reports about abiotic pollination in orchids are meagre. In some taxa the self pollination has been reported due to the degeneration of the rostellum or its becoming stigmatic or simple falling of the old pollinarium on the receptive surface of the stigma. This has been attributed to an alternate device to avert sterility at the end of a long normal period when the flower is open but no pollinators arrive. A kind of mechanical self-pollination due to the bending down of the tissues connecting to the viscidium and the pollinia has also been reported in Orchids in Europe and in Epidendrum nocturnum and Bletia purpuria in Florida where the customary pollinators of these taxa are absent.. However, in the present paper a similar last resort of previously unreported abiotic mode of self-pollination due to bending of the pollinaria bearing apical portion of the column has been reported in Cymbidium sinense, in cultivated individuals at Mokokchung, Nagaland.

Keywords : Cymbidium sinense, self-pollination, Nagaland

 

 

Reproductive Biology of Duranta repens L. (Verbenaceae) in Relation to its Environment

Divya Sharma & Anita Rana
Department of Botany, School of Life Sciences, Dr. B.R. Ambedkar University, Agra - 282 002, India
e-mail : divyasharma_agra@yahoo.co.in

ABSTRACT

Impact of environmental changes (temperature and RH) on reproductive biology in Duranta repens (Verbenaceae) growing at ten different sites of Agra was studied. It flowers throughout the year, with optimum flowering in September. The flowers are arranged in loose clusters on terminal or axillary racemes. They are either blue or lavender in colour, hermaphrodite, actinomorphic and complete. The plants exhibit floral polymorphism (increase and decrease in number of petals and stamens) and considerable variation in extent of pollen fertility, floral density, insect pollinators and fruit-set percentage. The changes in temperature and relative humidity during the entire flowering period, was found associated with the variation in floral structure, pollen fertility and fruit-set percentage. Based on the percentage of fruit-set during different seasons of a year, there were three distinct periods, namely maximum, moderate and minimum periods. The present paper deals with the comparative view of reproductive biology of this ornamental plant in these periods. During the months of August- November when temperature ranges between 13.7-36.6ºC and RH between 79-89 % the plant exhibits maximum fruit-set percentage (68-85%). This was associated with maximum flowering, increase in floral size, and increase in visitation rates of pollinators and higher degree of pollen fertility. On the other hand, with temperature reaching to the maximum (15.1-41.5ºC) and reduction in RH (14.1- 41.3%), the percentage of fruit-set was reduced to the minimum (21-30%). During this period, number of flowers/plant, floral size, pollen fertility, visitation rates of pollinators were reduced to the minimum. During this period floral polymorphism was also recorded.

Keywords : Duranta repens, fruit-set, relative humidity, temperature, floral polymorphism, pollinators, pollen fertility

The Effect of Blossom Structure and Nectar Composition of Some Raspberry and Blackberry
Cultivars on the Behaviour of Pollinators

K. Schmidt, Zs. Orosz-Kovács and Á. Farkas
University of Pécs, Institute of Biology, Department of Plant Systematics and Geobotany, 7624 Pcs, Ifjúság u. 6., Hungary
University of Pécs, Medical School, Institute of Pharmacognosy, 7624 Pécs, Rókus u. 2., Hungary
e-mail : schmidtk@freemail.hu

ABSTRACT

Various berry fruit flowers were studied focusing on primary and secondary attractants that influence the behaviour and preferences of pollinators. The studied cultivars included raspberries (Rubus idaeus L.), blackberries (R. caesius L.) and their hybrids that are grown currently in Hungary. From primary attractants nectar was studied in detail, determining daily nectar yield and sugar content, as well as nectar sugar composition for each studied cultivar. The most characteristic difference in nectar composition was that sucrose was found only in traces in raspberry, whereas its concentrations were high both in blackberries and hybrids. From secondary attractants emphasis was laid on floral morphology, including flower structure and colour, deviations from the pentameric character of rosaceous flowers and position of the nectary. Characteristic pollinators were identified for each cultivar, and numbers of insect visits were recorded. The most abundant visitors were honeybees and bumblebees, but on the flowers of some cultivars various ants and chrysops were observed, as well.

Keywords : Rubus idaeus, R. caesius, blossom structure, nectar composition, pollinators

Flower Biology and Fertility Relations of Some Local Hungarian Quince (Cydonia oblonga Mill.) Cultivars

H. Nagy-Déri, Zs. Orosz-Kovács and Á. Farkas
Plant Ecology Research Group of Hungarian Academy of Sciences, Institute of Botany and Ecophysiology,
Faculty of Environmental and Agricultural Sciences, Szent István University, H-2103 Gödöllõ, Páter K. u. 1., Hungary
Dept. of Botany, Faculty of Natural Sciences, University of Pécs, H-7624 Pécs Ifjúság u. 6., Hungary
Institute of Pharmacognosy, Medical School, University of Pécs, H-7624 Pécs, Rókus u. 2., Hungary

e-mail : helga@gamma.ttk.pte.hu

ABSTRACT

Flower biological studies were conducted in some local Hungarian quince cultivars. The aim of the investigations was to find characters which can refer to the fertility relations of the cultivars. The investigated cultivars of Cydonia oblonga had homogamous or delayed homogamous flowers in which the first phase was protogyny. On the basis of the active period of sexual organs it can be established that the degree of homogamy was the highest in cv. ‘Váli’, which was followed by cvs. ‘Champion’, ‘Mezõtúri’ and ‘Bereczki bõtermõ’. The most dichogamous one was cv. ‘Perbál I.’. This cultivar also had the most characteristics which indicate that flowers aspire to cross-pollination. On the other hand, cv. ‘Champion’ possessed the most of the self-fertile features. As a rule, quince cultivars are allogamous but delayed autogamy can provide an alternative opportunity for reproduction.

Keywords : Cydonia oblonga, flower biology, pollen, stigma, nectar production, quince, reproduction, self-sterility, self-fertility, pollinator, pollination

Stigma Behaviour in Incarvillea emodi (Bignoniaceae)

Susheel Verma , Rani Magotra, Namrata Sharma and A.K. Koul
Centre for Biodiversity Studies, School of Biosciences and Biotechnology, BGSB University, Rajouri - 185 131
Department of Botany, University of Jammu, Jammu . 180 006

e-mail : eremurus@rediffmail.com

ABSTRACT

The bilobed stigma of Incarvillea emodi closes in response to touch. The closing and reopening is rapid in freshly open flowers and is delayed in older ones. The causes of stigma closure and its subsequent reopening in Incarvillea emodi was investigated experimentally. Stigma closure is caused both by touch and pollen, but closure in response to pollen is slower. Upon receipt of sufficient pollen to sire the ovules present in the ovary, the stigmas stay permanently closed. The experiments were conducted to study the significance of this kind of stigma behaviour in the species. A positive correlation between pollen load, pollen germination and ovule number in case of closed as well as open stigmas was observed.

Keywords : Incarvillea emodi, stigma, closing, reopening, pollination

The Physiological Role of the Seed-set on the Flowering and Fruit Development in Some Temperate Fruit Crops

Jozsef Racsko, Miklos Soltesz, Zoltan Szabo and Jozsef Nyeki
Department of Horticulture and Crop Science, The Ohio State University, OARDC, 1680 Madison Avenue,
OH 44691 Wooster, USA
Institute for Research and Development, University of Debrecen, 138 Boszormenyi street, 4032 Debrecen, Hungary

ABSTRACT

Except for the rare cases of apomixes, seed development is supposed to be preceded by fertilization. In this review paper, the authors discuss the physiological role of the seeds in various fruit crops such as apple (Malus domestica), pear (Pyrus communis), quince (Cydonia oblonga) and currants (Ribes spp.) which is closely related to the cropping habit of a tree. Higher specific seed-set is characteristic when trees bear a relatively heavier load. The ecological adaptability of fruit is weak if their seedset is relatively lower. Any stress, nutritional deficiency or drought, afflicts first those fruit, which contain less seed, so they are susceptible to be shed, preferably. Low seed-set may cause angular form of the fruit, too. Influence of the season and of rootstock on seed-set has also been reported. Seedset a fruit is a useful trait for checking the efficiency of insect and/or wind pollination, or the effect of distance of the pollen source of pollination. Growing fruit and their seeds greatly influence the flower bud initiation and the quality of the flowers by return bloom. Inhibition of flower formation caused by growing fruit is attributed with high probability to hormone synthesis in the developing seeds.

Keywords : Apple, pear, quince, currants, seed-set, fruit development, physiological and ecological factors

Morphological Differences in the Stigma of Fruitbearing and Fruitless Plants of Kigelia pinnata DC. (Bignoniaceae)

Anita Rana
Department of Botany, School of Life Sciences, Dr. B.R. Ambedkar University, Khandari Campus, Agra - 282 002, Uttar Pradesh (India)
e-mail : anita_rana21@rediffmail.com

ABSTRACT

Bilabiate and wet stigma of fruitless and fruit bearing Kigelia pinnata (Bignoniaceae) growing at Agra and Dehra Dun respectively exhibited morphological differences. The stigmatic lobes in the flowers of fruitless plants were smaller, dry and closed. The papillae on these stigmatic lobes were thick walled, compactly arranged and covered with thick intact cuticle-pellicle layer. On the other hand, stigmatic lobes in the flowers of fruit bearing plants were large, open and wet. The papillae on stigmatic surface were elongated, thin walled and loosely arranged. These were covered with a thin, disrupted cuticle-pellicle layer. The protoplast of mature papillae before anthesis consisted of dense cytoplasm with well-organized nucleus and other cytoplasmic organelles including mitochondria, golgi apparatus, ribosomes and several small vacuoles. On the other hand, the cytoplasm of stigmatic papillae of fruitless plants was highly vacuolated and the organelles were fewer in number and less organized.

Keywords : Kigelia pinnata, stigma, papillae, cuticle-pellicle layer

Premature Dissolution of Microsporocyte Callose Wall Causes Male Sterility in Ethephon Treated Cotton (Gossypium arboreum L.)

S.V.S. Chauhan , Meenu Chaudhary and Seema Chauhan
Department of Botany, School of Life School Sciences, Dr. B.R. Ambedkar University, Agra - 282 002, UP, India
e-mail : svs250@rediffmail.com; svsc07@gmail.com

ABSTRACT

Treatments with various concentrations of ethephon or ethrel (2, chloroethyl phosphonic acid) induced male sterility of variable degree. The plants treated with 0.2 and 0.3% ethephon exhibited 100% pollen sterility associated with tapetal malfunctioning. The cellsin this layer remained intact throughout major course of development. In the anthers of plants sprayed with 0.2% ethephon the callose (β-1, 3-glucan) wall that lies beneath the cellulose wall of the microsporocytes degenerated prematurely. On the other hand, the dissolution of callose wall occurred normally in the same or different anther locules. In both the cases, the resulting microspores were sterile. However, the wall of the microspores formed from the tetrads showing premature dissolution of callose wall was thin and devoid of characteristic spines. On the other hand, the microspores released from tetrads after normal callose wall dissolution in the same or different anther locule showed more or less normal exine with spines. The protoplast of pollen grains in both the cases was highly vacuolated and degenerated. Thus, ethephon induced male sterility in cotton is not only associated with tapetal abnormality but also due to premature dissolution of callose wall from the microspore tetrads.

Keywords : Gossypium arboreum, ethephon, callose wall, male sterility

Modern Characteristic Features of Cyanobacteria with Special Emphasis on Reproduction and Thallus Structure

Laxmipriya Koijam, S. Deepa Devi, O. Avijeet Singh, O.N. Tiwariand M. Rohinikumar Singh
Microbial Resources Division,Institute of Bioresources and Sustainable Development, Takyelpat, Imphal - 795 001, Manipur
e-mail : ontiwari1@rediffmail.com

ABSTRACT

Cyanobacteria are photosynthesis prokaryote possessing the ability to synthesize chlorophyll a. Typical water is the electron donor during photosynthesis, leading to the evolution of oxygen. Cyanobacteria have until recently also been characterized by their ability to form the phycobilin pigment, phycocyanin. It is the high concentration of this pigment occurring under some conditions which leads to the bluish colour of the organisms and hence both of the organisms are commonly known, cyanobacteria or bluegreen algae. However, it has increasingly become clear that at least some oxygen-evolving prokaryotes such as prochlorothris, which do not possess phycobilins, but do form chlorophyll b in addition to chlorophyll a are quite closely related to organisms with phycocyanin.

Studies of the Gametophyte Development and Reproductive Biology of an Endemic Tree Fern, Cyathea nilgirensis Holttum

P.B. Khare and Ruchi Srivastava
Pteridology Laboratory, National Botanical Research Institute, Lucknow – 226 001
(Council of Scientific and Industrial Research, New Delhi)

e-mail : kharepb@yahoo.com

ABSTRACT

There are eleven species of Cyathea occur in India of which C. nilgirensis is endemic to Nilgiri hills of South India. The species is threatened and also listed in the Red Data Book. Being tree habit and endemic status, the species is academically very significant; therefore investigation was carried out to study the reproductive biology in relation to its colonizing ability. Developmental stages of gametophytes and its morphology were studied. The spore germination was of Cyathea type and prothallial development of Adiantum type. Adult prothallus was cordate–thalloid having multicellular-branched hairs on its dorsal surface. The gametangial ontogeny was observed to be favourable for both intergametophytic as well as intragametophytic selfing but very less percentage of sporophytes were observed through intergametophytic selfing and no sporophytes were observed through intragametophytic selfing. The result indicated that the genetic diversity of the taxon is greater and through spores it could not be spread in the area of its occurrence which makes the taxon restricted to the defined area. The restrict distribution within South India corroborates the finding. Other details of reproductive biology were also discussed in the present communication.

Keywords : Cyathea nilgirensis, Endemic, Reproductive Biology, Tree Fern

Reproductive Biology of the Hamelia patens Jacq. (Rubiaceae) in Northern India

Seema Chauhan & Leonardo Galetto
Department of Botany, School of Life Sciences, Dr. B.R. Ambedkar University, Agra - 282 002
Instituto Multidisciplinario de Biologia Vegetal, Casilla de Correo 495, 5000 Cordoba, Argentina

e-mail : svs250@rediffmail.com; leo@imbiv.unc.edu.ar

ABSTRACT

A study of floral biology and the breeding system of Hamelia patens Jacq. (Rubiaceae) was carried out in northern India from March, 2005 to February, 2007. The data obtained was compared with those obtained from the original area of distribution of the species. This species is an ornamental shrub cultivated in the gardens for its beautiful orange-red bunches of flowers and copper green leaves. The tubular flowers are yellowish orange or orange-red, 3.05±0.12 cm long and last for three days. They are protrandous and the pollen is available 12-14 h before the stigma becomes receptive. The beginning of anthesis takes place between 0230-0300 h and the opening of the bifid stigma occur in the afternoon between 1430-1700 h. The nectar is secreted during both the male and female phases, with higher concentrations of sucrose. The floral biology is related to environmental factors, particularly temperature. The quantity of nectar and pollen fertility declines with the rise in temperature and in summers when temperature ranges between 37° C to 45° C, nectar was more or less absent and only 2-3% pollen were fertile. The flower visitors included honeybees, butterflies, wasps, house flies, ants and sunbirds. Ants and house flies are robbers whereas; all the others act as pollinators. Squirrels were frequently seen, but they just eat away the base of the flower full of nectar. The plant is selfcompatible and facultative xenogamous. The natural fruit-set is only 7% but seed-set rate is slightly higher. Thus, this species growing in its natural habitat in Argentina and in its cultivated form in India exhibits some differences in pollen fertility, stigma receptivity, nectar quantity and quality and behaviour of flower visitors and absence of hummingbirds from India. These are responsible for the difference in the reproductive success of this species at two places. It seems that this species is under the process of acclimatization in North India.

Keywords : Hamelia patens, nectar, pollen fertility, fruit-set, pollinators

Sexual System in Schleichera oleosa (Lour.) Oken (Sapindaceae)

Mayank Gautam, Vikas & Rajesh Tandon
Department of Botany, University of Delhi, Delhi . 110 007, India
e-mail : tandon.raj@gmail.com

ABSTRACT

The incidence of sexual dimorphism in flowering plants varies to different extents and it is highly scattered among the families of angiosperms. In order to establish the sexual system in a species it is essential to study the functional morphology of flowers and demonstrate the consistency in sex expression by recording phenological events in different years. We investigated these aspects in Schleichera oleosa (Sapindaceae), an important host tree usually cultivated for the commercial production of ‘Lac’. Earlier documentation on the sexual system of the species suggests a polygamodioecious condition. The present study, carried out on a set of 40 trees located at the northern spur of Aravalli, Delhi, for two years (2007 and 2008), however, demonstrated that S. oleosa exhibits subdioecy comprising male, female and andromonoecious trees. The andromonoecious trees exhibit lability in sex expression. On the basis of genet specific sexual morphs identified, it is inferred that subdioecy in the species has probably evolved through the gynodioecial pathway.

Keywords : floral biology, phenology, sex lability, subdioecy.

Phenology and Reproductive Biology of Withania somnifera (L.) Dunal (Solanaceae)

Vandana Singh
Department of Botany, School of Life Sciences, Dr. B.R. Ambedkar University, Agra – 282002, India
e-mail : vandana42@gmail.com

ABSTRACT

Withania somnifera L. Dunal. an important medicinal evergreen perennial herbaceous shrub flowers throughout the year. Optimum flowering is observed during August–November and February-April. The flowers in umbellate cyme are sessile, lurid yellow to dull green. The flowers open in the morning during summers and in the afternoon during winters. The flowers are highly protogynous as stigma becomes receptive much before anther dehiscence. In summers (May & June), 65-75% pollen grains are fertile, while in winters (October, November, February & March), the fertility increases (85-96%). An average of 3600 pollen grains is present for each ovule. Flexible floral morphology, particularly heterostyly, first prompts the flowers for cross-pollination but if failed the length of stamens increases to make them suitable for self-pollination. Withania somnifera has highly flexible mating systems and is facultative xenogamous. Out crossing is brought about by insects particularly large and small ants and bees. Autogamy and geitonogamy bring about high fruit and seed-set percentage. However, seed germination percentage is very low.

Keywords : Withania somnifera L., heterostyly, selfing, facultative xenogamy

 

Reproductive Biology of Pyrostegia venusta (Ker-Gawl.) Miers (Bignoniaceae) with Special Reference to Seedlessness

Sweety Singh, Seema Chauhan& Leonardo Galetto
Department of Botany, School of Life Sciences, Dr. B.R. Ambedkar University, Khandari Campus, Agra-282002, India
Instittuo Multidisciplinario de Biologia Vegetal, Casilla de Correo 495, 5000 Corodoba, Argentina

e-mail : sls_16_2004@yahoo.co.in; svs250@rediffmail.com; leo@imbiv.unc.edu.ar

ABSTRACT

Pyrostegia venusta (Ker-Gawl.) Miers syn. Bignonia venusta (Bignoniaceae), commonly known as “orange trumpet creeper”, “flame vine” or “golden shower” bears large number of orange tubular flowers arranged in dichasial cymes. There are four didynamous stamens and the gynoecium is bicarpillary, syncarpous with bilocular ovary, long style and bilabiate stigma. Various floral-polymorphic features e.g. increased number of stamens and stigmatic lobes and heterostyly are recorded in different flowers of the same individual. Flowers open in the morning between 6.00–7.30 am and remain open throughout the day and corolla abscises 12-14 h after anthesis. The flowers are protandrous as the stamens dehisce 1-2 h after their opening. A circular nectariferous tissue is present at the base of the ovary, secreting copious nectar throughout the life of flower. The stigma becomes receptive in the afternoon between 3.00 – 4.30 pm. However, the stigmatic lobes close down by various kinds of stimuli including self pollen, but reopens after some time. Only the honeybees, small bees and black ants visit the flowers, but are not effective pollinators as pollen grains on the stigmatic surface are either absent or only a few of them are present. Various hand pollination experiments conducted failed to produce fruits indicating that the plant is self-incompatible. The hand pollinated stigmatic surface shows only 2-3% pollen germination with small pollen tubes which fail to reach the ovules may be due to low temperature during the flowering period. Pollen-ovule ratio indicates that its facultative xenogamous nature.

Keywords : Pyrostegia venusta, floral biology, floral-polymorphism, pollination, self-incompatibility

 
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