Parts Of Pistil Research Articles

Whole-organ analysis of calcium behaviour in the developing pistil of olive (Olea europaea L.) as a tool for the determination of key events in sexual plant reproduction.

BackgroundThe pistil is a place where multiple interactions between cells of different types, origin, and function occur. Ca2+ is one of the key signal molecules in plants and animals. Despite the numerous studies on Ca2+ signalling during pollen-pistil interactions, which constitute one of the main topics of plant physiology, studies on Ca2+ dynamics in the pistil during flower formation are scarce. The purpose of this study was to analyze the contents and in situ localization of Ca2+ at the whole-organ level in the pistil of olive during the whole course of flower development.ResultsThe obtained results showed significant changes in Ca2+ levels and distribution during olive pistil development. In the flower buds, the lowest levels of detectable Ca2+ were observed. As flower development proceeded, the Ca2+ amount in the pistil successively increased and reached the highest levels just after anther dehiscence. When the anthers and petals fell down a dramatic but not complete drop in calcium contents occurred in all pistil parts. In situ Ca2+ localization showed a gradual accumulation on the stigma, and further expansion toward the style and the ovary after anther dehiscence. At the post-anthesis phase, the Ca2+ signal on the stigmatic surface decreased, but in the ovary a specific accumulation of calcium was observed only in one of the four ovules. Ultrastructural localization confirmed the presence of Ca2+ in the intracellular matrix and in the exudate secreted by stigmatic papillae.ConclusionsThis is the first report to analyze calcium in the olive pistil during its development. According to our results in situ calcium localization by Fluo-3 AM injection is an effective tool to follow the pistil maturity degree and the spatial organization of calcium-dependent events of sexual reproduction occurring in developing pistil of angiosperms. The progressive increase of the Ca2+ pool during olive pistil development shown by us reflects the degree of pistil maturity. Ca2+ distribution at flower anthesis reflects the spatio-functional relationship of calcium with pollen-stigma interaction, progamic phase, fertilization and stigma senescence.

Effects of Water-soluble Extracts from Different Pistil Parts on Self-incompatibility Suppression in Pomlo (<I>Citrus grandis</I>)

Effects of Water-soluble Extracts from Different Pistil Parts on Self-incompatibility Suppression in Pomlo (<I>Citrus grandis</I>)

Ethylene Synthesis and Auxin Augmentation in Pistil Tissues are Important for Egg Cell Differentiation after Pollination in Maize

The role of ethylene and auxin in stigma-to-ovule signalling was investigated in maize (Zea mays L.). Maturation of the egg cells in an ear was stimulated before actual fertilization by the application of fresh pollen grains or quartz sand to fully receptive stigmas. Ethylene emission by maize ears increased in response to those treatments. Silks and ovaries were involved in ethylene synthesis after pollen or sand was shed over the silks. The content of ethylene precursor [1-aminocyclopropane-1-carboxylic acid (ACC)] increased in both pistil parts soon after pollination. ACC rise was delayed by 4 h in the ovaries, and by 8 h in the silks after mock-pollination with sand. The auxin level increased rapidly in the silks and ovaries after pollination, and it was very high in the pollinated silks due to the high indole-3-acetic acid (IAA) content of pollen grains. IAA rise also appeared in the silks and ovaries after treatment with sand but it was delayed by 8 h. Application of ACC (10 microM) or IAA (6 microM) solutions to non-pollinated silks stimulated maturation of the egg cells. Moreover, the response of the egg cells to pollination was cancelled by l-alpha-(2-aminoethoxyvinyl)-glycine, alpha-aminoisobutyric acid or 2,3,5-triiodobenzoic acid applied to the silks before pollination. Thus ethylene synthesis and polar auxin transport in the silks pollinated with fresh pollen were necessary to evoke accelerated differentiation of the egg cells in maize ovules. Differences in pistil responses found between true- and mock-pollination suggest that signalling pathways are at least partially different for the reception of pollen grains and sand crystals on maize stigma.

S-RNase expressed in transgenic Nicotiana causes S-allele-specific pollen rejection.

Many angiosperms employ self-incompatibility systems to prevent inbreeding. The simple genetics of such systems have made them attractive models of plant cellular communication. Implicit in the single locus genetics is that only one or a few gene products are necessary for recognition and rejection of incompatible pollen. Results in the sporophytic system of the Brassicaceae suggest that different S-locus products are responsible for the pollen and pistil parts of the recognition and rejection response. In solanaeceous plants, which have a gametophytic self-incompatibility system, the S locus product responsible for the pollen portion of the interaction has not been identified, but ribonucleases encoded by the S-locus (S-RNases) are strongly implicated in the style part of the recognition and rejection reaction. In Nicotiana alata, pollen recognition and rejection occur if its S-allele matches either S-allele in the style. The putative stylar S-RNase is abundant in the transmitting tract, and pollen rejection may be related to action of S-RNase on pollen RNAs. Efforts to understand the molecular basis for pollen recognition and rejection have been limited by the lack of a system for manipulating and expressing S-RNases. Here we use the promoter of a style-expressed gene from tomato to obtain high levels of S-RNase expression in transgenic Nicotiana. Recognition and rejection of N. alata pollen S-alleles occur faithfully in the transgenic plants. Our results show that S-RNases alone are sufficient for pollen rejection in this system.

Crocus SativusPollen Tube Growth in Intra- and Interspecific Pollinations

SUMMARYPollen germination and pollen tube growth were studied by fluorescence technique in pistil of Crocus sativus and C. thomasii after intra- and interspecific pollinations. The results indicated that C. sativus pollen germinates in low percentage in all the stigmas and some pollen tubes grow down to the ovules. In both the Crocus species the pollen tube growth is accompanied by anormalities of pollen tube behaviour and its tip aspect. Since most of these abnormalities are found in all the pistil parts it was not possible to correlate them with incompatibility in the studied plants.

STUDIES ON POLLEN‐TUBE CHEMOTROPISM

Rosen, Walter G. (Marquette U., Milwaukee, Wis.) Studies on pollen‐tube chemotropism. Amer. Jour. Bot. 48(10): 889–895. Illus. 1961.—Pollen tubes of several species and hybrids of Lilium are attracted to certain pistil parts of Lilium in vitro. Positive chemotropism is observed with a variety of pistil‐pollen combinations and is independent of the compatibility of these combinations in vivo. The chemotropic factor can be extracted by steeping the pistil parts in water. Chemotropic activity is retained following freeze‐drying of pistil parts or extracts. The active material from L. longiflorum is heat‐labile, dialyzable and not precipitated by acetone. Under certain conditions it causes distention of the pollen tube wall. Chemotropic activity of pistil parts is not simulated by a variety of known compounds or by extracts from various sources other than pistils. A possible mechanism of action of the chemotropic factor is discussed.

Cucurbita-crosses. X. The osmotic pressure of different parts of pistil during the period from the morning of the day before anthesis to the afternoon of the flowering day.

1. According to the previous report(HAYASE and HIRAIZUMI 1955), the optimum sucrose concentration of artificial, media for pollen germination and growth varies with the age of pollen. In this report the authors attempted to investigate the relationship between the osmotic pressure of different parts of pistil and the age of pistil. 2. The osmotic pressure of the conducting tissue juice of the styles increased during the period from the morning the day before anthesis to the morning of the flowering day, while the ovary juice decreased during the same period. Therefore the difference of osmotic pressure between the style and ovary became gradually greater during that period (Table 1). 3. The refractometer reading of different parts of pistil varied with the age of pistil. The (refractometer)reading of stigma- and style-juice rise with the maturation, while that of ovary juice declined. This was similiar to the changes of osmotic pressure among the diff6rent parts of pistil during the same period (Table 2).

A STUDY OF CHEMOTROPISM OF POLLEN TUBES IN VITRO

Although much has been added to our knowledge concerning the requirements for pollen germination and pollen tube growth in recent years (1, 2, 4, 10, 17, 18), very little progress has been made in studying chemotropism of pollen tubes. Literature dealing with this subject prior to 1924 has been reviewed by Brink (3). There is an obvious lack of agreement among the different workers as to: (a) whether chemotropism of pollen tubes to pistil parts exists at all; and (b) if so, the role that chemotropism plays in directing the pollen tubes toward the egg. The present investigation is an attempt to further our knowledge of this process.