Stigma Constriction in Pearl Millet, a Factor Influencing Reproduction and Disease

Willingale, Julia; Mantle, Peter G.

doi:10.1093/oxfordjournals.aob.a086978

Cited by 17 publications

(7 citation statements)

References 4 publications

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“…Heslop-Harrison et al 1985a), indicating that the pollen tube tip does not secrete cellulase. Following the passage of a limited number of pollen tubes through the basal region of the silk, an abscission zone develops within hours, preventing the ingress of pathogens through the tissues of the silk Heslop-Harrison 1984, Y. Heslop-Harrison et al 1985a; similar events occur in other cereals; Willingale andMantle 1985, Y. HeslopHarrison andHeslop-Harrison 1997). The passage of the pollen tube ends after penetration of the micropyle and direct growth through the intercellular spaces of the subadjacent nucellus.…”

Section: )mentioning

confidence: 99%

The structure and prophylactic role of the angiosperm embryo sac and its associated tissues:Zea mays as a model

Heslop‐Harrison

1999

Protoplasma

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Summar3: Various developmental phases can be distinguished inthe definition of the archesporium and the early life of the embryo, taking Zea mays (maize) as a model within the family Gramineae, and other families where pertinent: (1) the isolation of the megasporocyte and the functional spore derived from it; (2) the maturation of the specialized walls of the embryo sac, and their reinforcement by ensheathments derived from the contiguous nucellar cells during a sequence of phased genetic ablation; (3) the differentiation of the synergids, the associated flange, and the filiform apparatuses; (4) the blocking of the pollen tube pathway by secondary secretions in the micropylar region and the coagulation of the pollen tube cytoplasm within the filiform apparatuses during the process of fertilization; and finally (5) the development of a compound cutinized envelope of four fused layers (six where the outer integument is also involved) after fertilization. For the nascent haploid generation, the period of maximum vulnerability in respect to both pathogen invasion and the transition from diplophase control occurs during these phases. It is concluded that many of the protective features form a prophylactic shield and are key components of the angiosperms in general, which may have contributed to their evolutionary success as a group. Other physiological or biochemical adaptations or barriers may also supplement the mainly structural features described here.

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Section: )mentioning

confidence: 99%

The structure and prophylactic role of the angiosperm embryo sac and its associated tissues:Zea mays as a model

Heslop‐Harrison

1999

Protoplasma

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“…A second potential function of the AZ is as a barrier preventing miscegenation, a function dramatically illustrated in pearl millet by the almost total blockage of sorghum tubes entering the zone, even when they have successfully traversed the distal parts of the stigma (HeslopHarrison 1982). As Willingale and Mantle (1985) have pointed out, the zone may also act as a self-incompatibility barrier, promoting outcrossing by preventing later selfpollination in highly protogynous pearl millet cultivars. A third significant function of the AZ in the pearl millet stigma, first recognized by Willingale and Mantle (1985) and Willingale et al (1986), is as a device regulating the period during which the ovary is open to invasion by pathogens.…”

Section: Discussionmentioning

confidence: 99%

“…As Willingale and Mantle (1985) have pointed out, the zone may also act as a self-incompatibility barrier, promoting outcrossing by preventing later selfpollination in highly protogynous pearl millet cultivars. A third significant function of the AZ in the pearl millet stigma, first recognized by Willingale and Mantle (1985) and Willingale et al (1986), is as a device regulating the period during which the ovary is open to invasion by pathogens. The rapid formation of a virtually complete seal at the entry into the ovary following a successful pollination ensures that the pathway for potentially invasive hyphae is rapidly blocked.…”

Section: Discussionmentioning

confidence: 99%

“…The operation of the abscission system could be critically important not only in regulating pollination but also in providing a barrier to infection after the end of the pollenreceptive period. Willingale and Mantle (1985) and Willingale et al (1986) provided the first direct evidence for this in a detailed study of the role of the activatable zone in resistance to ergot, discussed below. We report here on cytological features of the AZ of millet and comment on various aspects of the physiology of the abscission process itself, including the role of the calcium oxalate druses copiously distributed in the cells of the AZ.…”

Section: Introductionmentioning

confidence: 92%

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The pollen tube activated abscission zone in the stigma of pearl millet: structural and physiological aspects

Heslop‐Harrison¹,

Heslop‐Harrison²

1997

Can. J. Bot.

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Abscission of the stigmas of pearl millet (Pennisetunl typhoides (Burman) Stapf et Hubbard) after pollination results from the activation of a specialized zone of tissue near the base. This abscission zone comprises a well-defined stretch of the basal column made up of thin-walled cells lacking a cuticularized epidermis. The penetration of the first few pollen tubes following a compatible pollination results in loss of turgor throughout the tissue, followed by loss of adhesion between the cells and ultimately disruption of the whole zone. Pectolytic enzymes are released concomitantly, but the cellulosic skeletons of the cells persist. Numerous calcium oxalate druses, identified cytochemically and by energy-dispersive X-ray analysis, are present in the cells of the abscission zone; these undergo dissolution after activation of the zone, while simultaneously the druse population in the stigma stump and the upper ovary wall increases. The barrier formed by the degenerating abscission zone tissues excludes pollen tubes arriving after the initial activation and prevents the penetration of pathogens such as ergot and so has a prophylactic role. We suggest that the collapsed abscission zone forms not only a physical barrier but also a chemical one. Dissolution products of the numerous calcium oxalate druses during the breakdown of the tissue are likely to raise the calcium ion concentrations beyond the optimum for pollen-tube growth, thereby preventing further penetration. Inhibited tubes swell at the tips and may show growth disorientation before arrest, responses similar to those seen in pearl millet tubes in culture when exposed to higher than normal calcium ion concentration.Resum6 : L'abscission des stigmates du millet perlt (Penniseturn typhoides (Burman) Stapf et Hubbard), aprks la pollinisation, rtsulte de I'activation d'une zone sptcialiste du tissus situC a sa base. Cette zone d'abscission comporte une portion bien dCfinie de la colonne basale, constitute de cellules i paroi mince dCpourvues d'Cpiderme cuticularist.La penetration du premier grain de pollen, i la suite d'une pollinisation compatible, conduit i une perte de turgescence dans l'ensernble du tissus, suivi par une perte de cohtsion entre les cellules et tventuellement d'une dCsorganisation de I'ensemble de la zone. Des enzymes pectolytiques sont reldchtes i ce moment mais le squelette cellulosique des cellules persiste. De nombreux cristaux d'oxalate de calcium, identifiCs cytochimiquement et par I'tnergie dispersive des rayons X, sont prtsents dans les cellules de la zone d'abscission; ceux-ci subissent une dissolution aprks l'activation de la zone, alors que simultanCment la population de cristaux dans la base du stigmate et dans la partie suptrieure de l'ovaire augmente. La barrikre formte par les tissus de la zone d'abscission en dCgtntrescence exclut les tubes polliniques qui arrivent aprks l'activation initiale et prtvient la ptnttration par des organismes pathogknes tels que I'ergot, comportant ainsi des proprittts prophylactiques. Les auteur...

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“…The vascular system, transmitting tissue and stylar canal (located in the union of both arms of the style) can be identified in pistils of fertile sorghum flowers prior to anthesis (Pizzolato 1991). The transmitting tissue is a specialized group of cells designed for pollen tube growth and has been observed in grasses such as Pennisetum glaucum (Willingale & Mantle 1985) and Z. mays (Westgate & Boyer 1986), as well as in dicotyledons such as Brugmansia suaveolens (Hudak et al 1993). This is the first report on a male-sterile sorghum line showing the style with compact tissues before and after pollination (Figs 1 and 2), without any channel inside.…”

Section: A-and B-line Traitsmentioning

confidence: 99%

Pollen–pistil interaction, pistil histology and seed production in A×B grain sorghum crosses under chilling field temperatures

et al. 2009

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SU MMARYSix pairs of isogenic lines of sorghum (Sorghum bicolor L. Moench) were sown in field plots in Montecillo, State of Me´xico (2240 m altitude), in 2005 and 2006. Crosses A (Y)rB (X) were done in each pair. In A-lines, the length of pistil, stigma, style and ovary, as well as the ovary width, were measured. In B-lines, pollen diameter, viability (cytoplasm density) and production were evaluated. Pollen germination and pollen tube growth in the pistils of the A-lines, were quantified in vivo with aniline blue and epifluorescence 18 h after pollination (HAP), while fertilized pistils were counted at 96 HAP. Histological studies on both pollinated and non-pollinated pistils were performed in one male-sterile line. Seed yield, mean-seed weight, seeds per panicle and seed set (SS; seeds/flower/ panicle) were determined at harvest. Pollen viability was the variable most related to pollen germination and pollen tube growth. Stigma receptivity was not associated with its morphology

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Stigma Constriction in Pearl Millet, a Factor Influencing Reproduction and Disease

Cited by 17 publications

References 4 publications

The structure and prophylactic role of the angiosperm embryo sac and its associated tissues:Zea mays as a model

The structure and prophylactic role of the angiosperm embryo sac and its associated tissues:Zea mays as a model

The pollen tube activated abscission zone in the stigma of pearl millet: structural and physiological aspects

Pollen–pistil interaction, pistil histology and seed production in A×B grain sorghum crosses under chilling field temperatures

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