1 The Basic Features of Self-Incompatibility.- 2 The Genetics of Self-Incompatibility.- 3 Cellular and Molecular Biology of Self-Incompatibility.- 4 Breakdown of the Self-Incompatibility Character, S Mutations and the Evolution of Self-Incompatible Systems.- 5 Incompatibility and Incongruity Barriers Between Different Species.- 6 Conclusions.- References.

Incompatibility and Incongruity in Wild and Cultivated Plants

The characteristics of pollen tube growth are not constant, but display distinct patterns of growth within the different tissues of the pistil. In the stigma, the growth rate is slow and autotrophic, whereas in the style, it is rapid and heterotrophic. Very little is known about the interactions between these distinct maternal tissues and the traversing pollen tube and the role of this interaction on the observed metabolism. In this work we characterise pollen tube growth in the apple flower and look for differences in glycoprotein epitope localization between two different maternal tissues, the stigma and the style. While immunocytochemically-detected arabinogalactan proteins were present at high levels in the stigma, they were not detected in the transmitting tissue of the style, where extensins were abundant. Whereas extensins remained at high levels in unpollinated pistils, they were no longer present in the style following pollen tube passage. Similarily, while abundant in unpollinated styles, insoluble polysaccharides such as β-glucans, were depleted in pollinated pistils. The switch from autotropic to heterotrophic pollen tube growth correlates spatially with a change of glycoprotein epitopes between the stigma and the style. The depletion of extensins and polysaccharides following pollen tube passage in the style suggest a possible contribution to the acceleration of heterotrophic pollen tube growth, which would imply an active contribution of female tissues on prezygotic male–female crosstalk.

/pdf/glycoprotein-composition-along-the-pistil-of-malus-x-25o3iu8qij.pdf

Glycoprotein composition along the pistil of Malus x domestica and the modulation of pollen tube growth.

A floral transmitting tissue-specific glycoprotein attracts pollen tubes and stimulates their growth

Publisher Summary Pollen germination and pollen-tube growth events when viewed either in culture or in the style are considered as biochemically, physiologically, and structurally complex. The various processes involved are each independent in some measure, but still all are interactive—namely, the successful attainment of the delivery of two male gametes into the embryo sac, requires a high degree of coordination within the male gametophyte and at the same time a remarkable sensitivity to a considerable range of influences both in the physical environment and in the pistil. Much of the activity of the vegetative cell has the air of being preprogrammed; and this must be so in those species where there is little or no gene transcription in the vegetative nucleus. The capacity to function successfully in a complex and varying environment betokens a high degree of self-regulation. Some of the feedback mechanisms likely to contribute to stability are reviewed. They are analogous with the homeorhetic systems postulated in other instances of biological development. However, two features make the angiosperm male gametophyte almost unique among higher organisms, namely the versatility expressed by a single haploid cell, and the degree of coadaptation it shows with its diploid host.

Pollen germination and pollen-tube growth

Successful pollination and fertilization are absolute requirements for sexual reproduction in higher plants. Pollen hydration, germination and penetration of the stigma by pollen tubes are influenced by the exudate on wet stigmas and by the pollen coat in species with dry stigmas. The exudate allows pollen tubes to grow directly into the stigma, whereas the pollen coat establishes the contact with the stigma. Pollen tubes then grow into the papillae, which are covered by a cuticle. The components of the exudate or pollen coat that are responsible for pollen tube penetration are not known. To discover the role of the exudate, we tested selected compounds for their ability to act as functional substitutes for exudate in the initial stages of pollen-tube growth on transgenic stigmaless tobacco plants that did not produce exudate. Here we show that lipids are the essential factor needed for pollen tubes to penetrate the stigma, and that, in the presence of these lipids, pollen tubes will also penetrate leaves. We propose that lipids direct pollen-tube growth by controlling the flow of water to pollen in species with dry and wet stigmas.

Lipids are required for directional pollen-tube growth

Detached pistils of Lilium longiflorum were labeled with d-glucose-U-(14)C 24 hours after anthesis and then sampled for the next 6 days to determine the appearance of label into exudate from the stylar canal and the stigmatic surface of the pistil. Results were obtained with unpollinated cv. Ace pistils and pollinated cv. Ace pistils, selfed or crossed (cv. Croft pollen). Limited data were also obtained on cv. Croft pistils, selfed or crossed (cv. Ace pollen).Exudate appeared in the canal and on the stigmatic surface soon after anthesis. In unpollinated pistils it continued to accumulate for about 5 days in the canal and for the full term of the experiment, 7 days, on the stigmatic surface. Canal exudate eventually mixed with stigmatic exudate in unpollinated pistils. Pollination interrupted the flow of exudate, and a portion of the pistil secretion product was diverted toward the synthetic requirements of the developing pollen tubes. Two days after pollination, the specific radioactivity of pollen tube cytoplasm had reached a level comparable to canal exudate. Twenty-four hours later, the specific radioactivity of pollen tube wall substance was about 80% of the value found in canal exudate. Similar patterns of (14)C incorporation and similar carbohydrate contents were obtained from self- and cross-pollinated pistils, although the former contained pollen tubes of less than one-half the length of the latter.

The Nutritional Role of Pistil Exudate in Pollen Tube Wall Formation in Lilium longiflorum II. Production and Utilization of Exudate from Stigma and Stylar Canal

A quantity of labeled stigmatic exudate, collected from detached Lilium longiflorum (cv. Ace) pistils labeled with d-glucose-1-(14)C, was fractionated on Sephadex G-100 and the polysaccharide component, G-100-I, was injected into the hollow styles of unlabeled detached pistils (cv. Ace) which had been removed on the day after anthesis from the plant. Injected pistils were immediately cross-pollinated with L. longiflorum (cv. No. 44) pollen. Eighty-four hours later, pistils were dissected to recover the pollen tubes, expended exudate, and labeled tissues of the stigma and style. Distribution of label revealed that at least 25% of the carbohydrate substance in excised pollen tubes was derived from G-100-I. The composition of expended exudate adhering to pollen tubes, of pollen tube cytoplasm, and of pollen tube walls suggests that utilization of exudate by growing pollen tubes involves uptake and incorporation into pollen tube cytoplasm of exudate polysaccharide fragments followed by extensive metabolism of at least a portion of the incorporated carbohydrate prior to its utilization for pollen tube wall biosynthesis. Results suggest the presence of at least two polysaccharide components in G-100-I, one which resists major degradation following injection into the style and another which undergoes measurable degradation both before and after entry into the pollen tube.

The Nutritional Role of Pistil Exudate in Pollen Tube Wall Formation in Lilium longiflorum: I. Utilization of Injected Stigmatic Exudate.

Stigmatic exudate, a secretion product recovered from the upper surface of Lilium longiflorum pistils, has been examined. Over 99% of the exudate is accounted for as water, carbohydrate, and protein. Exclusive of water, 95% is a high molecular weight, protein-containing polysaccharide composed of galactose, arabinose, rhamnose, glucuronic acid, and galacturonic acid.Detached pistils supplied with myo-inositol-U-(14)C, myo-inositol-2-(3)H, d-glucose-1-(14)C, or l-proline-U-(14)C produce labeled stigmatic exudate. When myo-inositol is supplied, the exudate is rich in labeled arabinose and uronic acids, but some label also recycles through the hexose phosphate pool of secreting cells, causing label to appear in galactose and rhamnose residues. When glucose is provided, galactose is the major constituent labeled but all of the other carbohydrate constituents are also labeled. Proline produces a pattern very similar to that obtained with glucose.Stigmatic exudate also contains a small amount of low molecular weight carbohydrate. If myo-inositol is used to label exudate, free labeled myo-inositol cannot be detected in the low molecular weight fraction until it has been subjected to acid hydrolysis. Similarly, if d-glucose is the source of label, free labeled glucose is found in the low molecular weight fraction only after acid hydrolysis.

http://www.plantphysiol.org/content/plantphysiol/46/1/150.full.pdf

The Composition of Stigmatic Exudate from Lilium longiflorum Labeling Studies with Myo-inositol, d-Glucose, and l-Proline

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

C. Labarca

Author Tools

Chat about Author

Papers

The Nutritional Role of Pistil Exudate in Pollen Tube Wall Formation in Lilium longiflorum II. Production and Utilization of Exudate from Stigma and Stylar Canal

The Nutritional Role of Pistil Exudate in Pollen Tube Wall Formation in Lilium longiflorum: I. Utilization of Injected Stigmatic Exudate.

The Composition of Stigmatic Exudate from Lilium longiflorum Labeling Studies with Myo-inositol, d-Glucose, and l-Proline