Programmed cell death of Pinus nucellus in response to pollen tube penetration

In ovules of Pinus densiflora, pollen tubes elongate and branch into the nucellar tissue in the direction of the female gametophyte. After pollination, nucellar cells located around the pollen grain and tube die off. We showed here that the nuclei of the nucellar cells were stained by TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP-fluorescein nick end labeling). The number of TUNEL-positive cells increased during pollen tube growth. The tips of pollen tube branches protruded into the nucellar cells to form a convex-concave junction. At this junction, the cell membrane of nucellar cells was separated from the cell wall and the protoplast shrank. Small vesicles and amorphous materials were released from the protoplast into the space between the cell membrane and wall. Vacuoles were collapsed, chromatin was condensed, and mitochondria and plastids were deteriorated in the shrunken protoplast. Agarose gel analysis of DNA isolated from the ovules showed a DNA ladder, suggesting that the nuclear DNA had undergone internucleosomal cleavage. These results suggest that nucellar cells undergo programmed cell death in response to pollen tube penetration with some features resembling apoptosis and other features peculiar to nucellar cells.     

Self-incompatibility in Acacia retinodes: Site of pollen-tube arrest is the nucellus

In self-incompatible Acacia retinodes Schldl. var. uncifolia J.M. Black there is no inhibition of self pollen tubes before entry into the ovule, but the frequency of fertilized embryo sacs observed after self pollination is only 0.09–0.24 of that observed after outcrossing. Fluorescence- and light-microscope studies of sectioned, squashed or cleared whole ovules indicate that most self pollen tubes are arrested within the first or second layer of cells of the nucellus. The probability that nucellar arrest represents a primitive feature of self-incompatibility is discussed.     

Pollination in conifers

Our understanding of pollination in conifers has advanced rapidly in recent years, but it still lags behind our knowledge of this process in angiosperms. In part this is because conifers are not considered to be high priority crops and, unlike many cultivated flowers, conifer seed cones are generally neither large nor colorful. The use of genetics to improve tree growth has primarily been through selection and asexual propagation rather than breeding, and because incompatibility is not thought to occur in conifer pollination systems, concern about pollination has primarily been with regard to seed production. Here we examine the ancestral wind-pollination mechanism in conifers and discuss how the process may have evolved to improve pollination success.     

Programmed cell death of Pinus nucellus in response to pollen tube penetration

In ovules of Pinus densiflora, pollen tubes elongate and branch into the nucellar tissue in the direction of the female gametophyte. After pollination, nucellar cells located around the pollen grain and tube die off. We showed here that the nuclei of the nucellar cells were stained by TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP-fluorescein nick end labeling). The number of TUNEL-positive cells increased during pollen tube growth. The tips of pollen tube branches protruded into the nucellar cells to form a convex–concave junction. At this junction, the cell membrane of nucellar cells was separated from the cell wall and the protoplast shrank. Small vesicles and amorphous materials were released from the protoplast into the space between the cell membrane and wall. Vacuoles were collapsed, chromatin was condensed, and mitochondria and plastids were deteriorated in the shrunken protoplast. Agarose gel analysis of DNA isolated from the ovules showed a DNA ladder, suggesting that the nuclear DNA had undergone internucleosomal cleavage. These results suggest that nucellar cells undergo programmed cell death in response to pollen tube penetration with some features resembling apoptosis and other features peculiar to nucellar cells. Received: April 13, 2001 / Accepted: December 10, 2001     

传粉对杭州石荠苎（唇形科）结实的影响

杭州石荠苎（ＭｏｓｌａｈａｎｇｃｈｏｕｅｎｓｉｓＭａｔｓｕｄａ）自交亲和,人工自花授粉,同株异花授粉和异花授粉的结实没有明显差异。杭州自然居中新开花朵的调查没有发现闭花传粉现象。原因是花药和柱头之间存在空间隔离和发育上的时间隔离。这些隔离使昆虫花粉传播的必要媒介,结实从而取决于传粉昆虫的活动。     

Pollination by brood-site deception

Pollination is often regarded as a mutualistic relationship between flowering plants and insects. In such a relationship, both partners gain a fitness benefit as a result of their interaction. The flower gets pollinated and the insect typically gets a food-related reward. However, flower-insect communication is not always a mutualistic system, as some flowers emit deceitful signals. Insects are thus fooled by irresistible stimuli and pollination is accomplished. Such deception requires very fine tuning, as insects in their typically short life span, try to find mating/feeding breeding sites as efficiently as possible, and following deceitful signals thus is both costly and time-consuming. Deceptive flowers have thus evolved the ability to emit signals that trigger obligate innate or learned responses in the targeted insects. The behavior, and thus the signals, exploited are typically involved in reproduction, from attracting pheromones to brood/food-site cues. Chemical mimicry is one of the main modalities through which flowers trick their pollen vectors, as olfaction plays a pivotal role in insect-insect and insect-plant interactions. Here we focus on floral odors that specifically mimic an oviposition substrate, i.e., brood-site mimicry. The phenomenon is wide spread across unrelated plant lineages of Angiosperm, Splachnaceae and Phallaceae. Targeted insects are mainly beetles and flies, and flowers accordingly often emit, to the human nose, highly powerful and fetid smells that are conversely extremely attractive to the duped insects. Brood-site deceptive plants often display highly elaborate flowers and have evolved a trap-release mechanism. Chemical cues often act in unison with other sensory cues to refine the imitation.     

Purification and Biological Activities of Abelmoschus esculentus Seed Lectin

The Abelmoschus esculentus (Malvaceae) plant originated in Africa and has spread across a number of tropic countries, including northeastern Brazil. The plant has been used to treat various disorders, such as cancer, microbial infections, hypoglycemia, constipation, urine retention and inflammation. The lectin of A. esculentus (AEL) was isolated by precipitation with ammonium sulfate at a saturation level of 30/60 and purified by ion exchange chromatography (Sephacel-DEAE). The electrophoresis (SDS-PAGE) profile of the AEL showed two protein bands of apparent molecular mass of approximately 15.0 and 21.0?kDa. The homogenity of the protein was confirmed by electrospray mass spectrometry (ESI-MS), which revealed the presence of a 10.29-kDa monomer and a 20.58-kDa dimer. The AEL exhibits agglutinating activity against rabbit (74.41 UH/mP) and human type ABO erythrocytes (21.00 UH/mP). This activity does not require the presence of divalent cations and is specifically inhibited by lactose, fructose and mannose. The intravenous treatment with 0.01, 0.1 and 1?mg/kg of AEL inhibited the paw edema elicited by carrageenan by approximately 15, 22 and 44?%, respectively, but not that induced by dextran. In addition, treatment with 0.1, 1 and 10?mg/kg of AEL also inhibited the abdominal writhing induced by acetic acid by approximately 52, 57 and 69?%, respectively. In conclusion, AEL is a new lectin with a molecular mass of 20.0?kDa, which is -composed of a 10.291-Da monomer and a 20.582-kDa dimer, that exhibits anti-inflammatory, antinociceptive and hemagglutinating activities. In addition, the lectin hemagglutinating property is both metallo-independent and associated with the lectin domain.     

Pollination and flower diversity in scrophulariaceae

The Botanical Review - The flowers of the Scrophulariaceae show a great diversity in form, especially of the corolla. The most common pollinators are bees collecting nectar, pollen, or oil; other...     

Pollination ofOpuntia lindheimeri and related species

The large, yellow, bowl-shaped flowers ofOpuntia lindheimeri, O. discata, O. phaeacantha major, andO. compressa in Texas are visited by various species of beetles and bees. The beetles and small bees (Perdita, Dialictus) are pollen thieves. The pollinators are the medium-sized and larger bees (Melissodes, Diadasia, Lithurge, Megachile, Agapostemon, etc.). Different species of theOpuntia lindheimeri group have the same pollination system and there is no evidence of any floral isolation between them. The pollination system of these species ofOpuntia in Texas is essentially the same as that ofEchinocereus fasciculatus andFerocactus wislizeni in Arizona.Pollination of North American Cacti, II.—SeeGrant & Grant (1979).     

Physicochemical and Binder Properties of Starch Obtained from Cyperus esculentus

The purpose of this study was to isolate starch from the tubers of Cyperus esculentus L. and evaluate its physicochemical and binder properties. Extraction of starch using sodium metabisulfite yielded 37 g of starch per 100 g of the tubers. Scanning electron microscopy indicated that Cyperus starch consists of oval to elliptical particles with a smooth surface. Cyperus starch demonstrates a narrow particle size distribution with a mean of 8.25 μm. Cyperus starch conforms well to United States Pharmacopeia standards established for widely used starches like maize and potato. The X-ray powder diffraction pattern and moisture sorption profile of Cyperus starch were comparable to that of maize starch. Cyperus starch had lower swelling power than maize and potato starch, indicative of stronger associative forces within the granules. Carr’s index and Hausner ratio indicate that Cyperus starch should have comparable flow properties with respect to maize and potato starch. Cyperus starch was employed as binder for the formulation of metronidazole tablets. Formulations containing 5%, 7.5%, and 10% Cyperus starch were compared with those containing 10% potato starch. At 10% binder concentration, the tablets containing Cyperus starch exhibited better hardness and negligible friability as compared with those with potato starch. Although the binder concentration had a significant effect on the disintegration time of the tablets, it did not seem to affect the dissolution profile. These results indicate that Cyperus starch provides excellent binding properties without compromising drug release characteristics and should be explored in pharmaceutical formulations.Key words: Cyperus esculentus, Cyperus starch, pharmaceutical excipient, physicochemical evaluation, starch characterization     

Seed development ofAbelmoschus esculentus (Malvaceae)

The endosperm is nuclear, cell wall initiation starts 5 days after pollination. During early stages endosperm nuclei exhibit synchrony in their division. Embryogeny is of the Asterad type. A7-to 10-celled suspensor persists up to the dicot stage of the embryo. Both integuments contribute towards formation of the seed coat. 30 days after pollination seeds become mature. Their endosperm is scanty and persists as a thin layer between the folds of the cotyledons. Nucellus remnants are present towards the funicular side.     

红豆杉的胚珠发育,传粉滴形成和传粉过程

观察了红豆杉（Ｔａｘｕｓ ｃｈｉｎｅｎｓｉｓ （Ｐｉｌｇ．）Ｒｅｈｄ）的花粉形态和水合特性及胚珠发育、传粉滴形成与传粉过程。成熟花粉为单细胞,无气吓,形状不规则,外壁表面具大量乌氏体。花粉水合时,内壁膨胀,外壁开裂。通常情况下,外壁保留在水滴或传粉滴的表面,而花粉的其他部分进入水滴或传粉滴内。在８月下旬,可观察到下弯的雌性生殖芽。下弯这一特性是雌性生殖芽区别于营养芽的重要特征。这一时期的雌性生殖芽     

Pollination and self-interference in Nothofagus

Interference between male and female functions within a monoecious plant may hinder crossing and decrease seed set. We assessed the probability of self-pollination and the effect of self-pollination on cross-pollination for two self-incompatible species: Nothofagus obliqua and N. nervosa. The probability of self-pollination was studied by tracking the phenologies of staminate and pistillate flowers, including an analysis of stigmatic receptivity. Pure and mixed pollinations were performed in order to evaluate the effect of self-pollination upon cross-pollination. Phenological observations suggest that self-pollination is highly likely in both species. Compared to pure cross-pollination, the application of self-pollination prior to cross-pollination resulted in lower numbers of germinated pollen grains for both species, and also in a lower production of viable seeds in N. nervosa. The low proportion of viable seeds often observed in natural populations of N. obliqua and N. nervosa may be related to self-pollination.     

Chasmogamous and Cleistogamous Pollination in Salpiglossis sinuata

Pollen from chasmogamous flowers of Salpiglossis sinuata L. could not be induced to germinate in vitro unless stigmatal extract was applied to the culture medium. The substance that induces pollen germination in the stigmatal extract is water-soluble and heat-stable. Crosses could not be achieved between chasmogamous and cleistogamous flowers because of structural incompatibility. Pollinated pistils of chasmogamous flowers release a large amount of ethylene. The burst of ethylene release is due to an interaction between pollen tubes and stylar tissue and is directly proportional to the quantity of pollen placed on the stigma. Cleistogamous flower buds also produce a burst of ethylene at the time of pollination within the closed flower. The ethylene release may be a cause of reduced corolla development associated with cleistogamous flowers.     

Pollination of the southwestern Opuntias

This paper presents an overview of pollination systems inOpuntia sens. lat. in the southwestern United States. The floral syndrome of large, colorful, bowl-shaped, diurnal flowers is present in all of the prickly-pear species and most of the cholla (Cylindropuntia) species in this area. Pollination by medium-sized and large bees is established for some of the species with this floral syndrome and is predicted for the others. The same floral syndrome is widespread inOpuntia in other geographical areas.—Deviations from this floral syndrome occur in certain species of southwestern chollas, one of which has nocturnal disc-shaped flowers, and in several tropical American species groups or segregate genera with red hummingbird flowers. But such cases are relatively infrequent. Divergence between species with respect to floral syndrome and pollination system is not a common feature in the evolutionary pattern ofOpuntia. Pollination of North American Cacti, IV.—Previons parts of this series:Grant & Grant 1979a,Grant & al. 1979,Grant & Grant 1979b.