泽苔草的花器官发生

本文用扫描电镜观察了泽苔草的花器官发生过程,观察结果表明：花萼以螺旋状方式向心发生,花瓣以接近轮状方式近同时发生,不存在花瓣雄蕊复合原基。雄蕊和心皮均以轮状向心方式发生,6枚雄蕊分两轮分别在对萼和对瓣的位置先后发生,至发育的后期排成一轮,但仍分别处于对萼和对瓣的位置;随后发生的第一轮3个心皮原基与3枚萼片相对,第二、三轮心皮原基分别为1~3个,与前一轮心皮相间排列向心发生。本文首次揭示了泽苔草花被的外轮3个萼片螺旋状发生方式,这种螺旋状方式很可能是泽泻科植物的花部结构在进化过程中适应环境而保留下来的一种较原始的叶性特征。     

Pistil induction by hormones from callus of <Emphasis Type="Italic">Oryza sativa</Emphasis> in vitro

This study describes the successful formation of floral organ pistil from the callus of pistil explants of Oryza sativa L. For induction of floral organs, different explants—including young embryo, lemma, palea and pistil—were used for callus induction with different combinations of N⁶-benzyladenine and 2,4-dichlorophenoxyacetic acid (2,4-D). High frequencies of callus formation from pistil and young embryo explants were achieved. Floral organs were induced after calli from pistils were transferred to medium containing both zeatin and 2,4-D. The morphological characteristics of the pistil-like organs are very similar to those formed in planta though with minor differences. Further histological study revealed that the in vitro pistil contains an ovule within its ovary. Furthermore, a pistil-specific gene, OsMADS3 used as a molecular marker for pistil identity, was expressed in the pistil-like organs as it was in pistils in the flower of the plant.     

Action of the Tunicate locus on maize floral development

The co-dominant Tunicate (Tu) mutation in maize causes nonreproductive structures in both the male and female inflorescences to be enlarged. This mutation also affects sex determination, permitting the development of pistils in the normally staminate tassel. In order to characterize the role of the normal tu gene product, we have analysed genetic interaction between Tu and other mutations that perturb specific stages of floral development. Synergistic interactions observed suggested that the tu product functions in at least three stages of floral development–determination of spikelet primordia, differentiation of non-reproductive organs and pistil abortion in the tassel. © 1994 Wiley-Liss, Inc.     

In vitro Transformation of Ovules into Rudimentary Pistils in Nicotiana tabacum L.

In our experiments with in vitro cultured young ovaries of Nicotianatabacum, var. havanensis we observed greening and extensivegrowth of the ovular primordia. Four to 6 weeks after inoculationa mass of rudimentary pistils bearing secondary ovules was tobe seen on the protruding placenta. Histological investigationproved these pistilloids not to be adventive organs arisingfrom callusing tissue, but the result of altered growth of theoriginal ovu1ar prirnordia. Though comparatively rare, reportson spontaneous ovular pistillody, including two Nicotiana species,exist in the teratological literature. However, whereas thesespon taneous ovular transformations are described as carpel-likestructures with marginally inserted secondary ovules, the invitro proliferating ovules develop into rudimentary pistilswith an early differentiating and very prominent central placenta.An interpretation of these differences is proposed.     

THE EFFECTS OF GIBBERELLIC ACID AND A GROWTH RETARDANT ON OVULE FORMATION AND GROWTH OF EXCISED PISTILS OF NIGELLA RANUNCULACEAE

The effects of gibberellic acid (GA₃) and the growth retardant AMO-1618 on ovule formation in excised pistils of Nigella sativa L. were studied by sterile culture techniques. Gibberellic acid promoted pistil growth and inhibited ovule formation. The role of endogenous gibberellins in ovule formation and pistil growth was investigated by adding AMO to the basal medium. Both pistil lengths and ovule formation were reduced significantly with increasing concentrations of AMO. The addition of low concentrations of GA₃ to the medium restored pistil growth but did not reverse the inhibitory effect of AMO on ovule formation. The addition of kinetin or indoleacetic acid (IAA) to the medium containing AMO had no effect on pistil lengths. However, with the addition of 10⁻⁷ m kinetin, the number of ovules in pistils was increased but not to the levels found in pistils grown in the absence of AMO.     

Ultrastructural and physiological differences between buds and mature flowers of Petunia hybrida prior to and following pollination

The structural events accompanying the maturation of the pistil of Petunia hybrida have been studied in detail, together with the changes in the protein spectrum of the transmitting tissue that occur over this period. These events have been considered in terms of the acquisition of the self-incompatibility response, which occurs while the pistil is enclosed in the bud. Apart from several minor differences, the young pistils differ only from the mature in that their transmitting tissue cells fail to respond to pollination by undergoing characteristic ultrastructural changes. Data from electrofocusing indicates that several proteins, mobilised in the mature transmitting tissue some three hours after pollination, are absent from bud pistils. It is proposed that the pollination-stimulated release of certain polypeptides, believed to be involved in the self-incompatibility response, does not take place in young pistils. These observations are considered with reference to currently-accepted models of the operation of the self-incompatibility mechanism in Petunia.     

Kinetics Studies on the Photoinduction of Xanthium strumarium L. and Isolation of a Flower Primordia Growth-Regulating Fractionl

The kinetics of flower primordia formation have been re-examinedin photoinduced Xanthium strumarium L. to determine the numberof short-day treatments that promote optimum primordia initiationand development. Plants given 4 short-day cycles showed thehighest rate of primordia development. Attempts were made toisolate flower-promoting substance(s) from the young leavesof such optimally induced plants by methanol extraction followedby ether fractionation. A Xanthium bioassay was developed fortesting the flower-promoting activity of aqueous concentratesobtained from the acidic, neutral-basic and total ether extracts.No flower-primordia inducing activity was found in any of thefractions, but growth-accelerating activity on young primordiawas shown by substance(s) present in the combined neutral-basicfraction isolated from photoinduced leaves. ¹C.R.D.A. Contribution No. 170. (Received June 14, 1989; Accepted September 20, 1989)     

Influence of drought stress on pistil physiology and reproductive success of two Gossypium hirsutum cultivars differing in drought tolerance

The causes of reproductive failure under drought stress (DS) are poorly understood. We hypothesized that reproductive failure was related to drought-induced changes in pistil biochemistry. To address this hypothesis, a water deficit-induced experiment was conducted with two cotton cultivars (Dexiamian 1, drought tolerant; Yuzaomian 9110, drought sensitive). Results showed that DS decreased the photosynthesis of subtending leaf and downregulated sucrose transporter gene (GhSUT-1) expression in pistil for both cultivars, resulting in lower pistil carbon accumulation which was reflected in the decreased starch accumulation. Lower starch, as potential energy, and adenosine triphosphate (ATP), as direct energy, in droughted pistils suggested less energy for pollen tube entrance into ovules, reducing the fertilized ovule number and fertilization efficiency. Further, although pistil peroxidase activity increased under DS, a higher hydrogen peroxide (H₂O₂) level still was measured in droughted pistils than well-watered pistils, damaging reproductive activities. Moreover, larger decreases in photosynthesis, pistil GhSUT-1 expression, carbon accumulation, starch and ATP contents caused by DS for Yuzaomian 9110 than Dexiamian 1, and different responses of superoxide dismutase and catalase activities, and ascorbic acid and H₂O₂ contents to DS between the two cultivars might be the reasons causing a greater decrease in fertilization efficiency for Yuzaomian 9110 than Dexiamian 1 under DS. Thus, we suggest that decreased ovule fertilization under DS was related to the disorganized carbohydrate metabolism and inefficient antioxidant defense in droughted pistils, and the effects of DS on pistil carbohydrate metabolism and antioxidant defense were more significant for drought-sensitive cultivars than drought-tolerant cultivars.     

Stigma-surface Esterase Activity and Stigma Receptivity in Some Taxa Characterized by Wet Stigmas

Stigma-surface esterase activity and stigma receptivity througha sequence of developmental stages of the pistil have been studiedin four taxa characterized by having wet stigmas — Petuniahybrida, Nicotiana tabacum, Crinum defixum and Amaryllis vittata.The style is solid in the first two and hollow in the lattertwo taxa. In all the taxa, stigma—surface esterase couldbe detected in a thin surface layer (pellicle) from a very earlystage of pistil development, irrespective of the presence orabsence of the exudate. However, the taxa showed variation instigma receptivity. In Petunia and Nicotiana, stigmas from pistilsof all the stages supported pollen germination and tube growth.In Amaryllis and Crinum, stigmas of only the mature pistils,when the exudate is present on the stigma, supported normalpollen germination and tube growth. It is inferred that in taxacharacterized by a wet stigma and solid style, the factors requiredfor pollen germination are present from an early stage of pistildevelopment and the exudate per se is not involved in pollengermination. In taxa characterized by a wet stigma and hollowstyle, however, the pellicle does not carry the factors requiredfor pollen germination and tube growth; they appear to be presentin the exudate. Petunia hybrida Vilm, Nicotiana tabacum L., Crinum defixum, Ker-Gawl, Amaryllis vittata Ait., tobacco, pollination, pollen germination, stigmatic exudate, stigma receptivity, stigma-surface esterase, esterase activity     

Pistil Structure and Pollen Tube Pathways in Leptospermum myrsinoides and L. continentale (Myrtaceae)

Pistil structure and pollen tube growth were investigated inLeptospermum myrsinoides and L. continentale (Myrtaceae). BothL. myrsinoides and L. continentale pistils consist of an ovarywith five locules, a style and a five-lobed dry, papillate stigma.A centrally located stigmatic cleft is present but extends onlyto the base of the stigma. Pollen germinates and grows intercellularlythrough the stigma into the central transmitting tissue of thestyle. Pollen tubes do not grow down the stigmatic cleft. Atthe base of the style the transmitting tissue separates intofive, each tract leading through the placenta to one of thefive locules. The pollen tubes continue to grow intercellularlythrough these five tracts entering the locules between the lobesof the placenta. Pollen tubes are smooth-walled and straightwhilst in the transmitting tissue of the style but produce shortlateral branches at regular intervals when in the locules. Branchingcontinues until pollen tubes enter ovules. It is suggested thatthe observed branching in the locules is a result of pollentubes following a chemotropic or thigmotropic pathway to theovules. This behaviour was consistent in all pistils examinedand no difference was observed in the behaviour of self- orcross-pollen tubes in the style or ovary.Copyright 1994, 1999Academic Press Leptospermum myrsinoides Schldl., Leptospermum continentale J. Thompson, pistil structure, pollen tube pathway, pollen tube branching     

Pollen size evolution: correlation between pollen volume and pistil length in Asteraceae

Based on the assumptions that pollen tube length is predetermined by provisions in the pollen and that it is a function of pistil length, I hypothesise that species with longer pistils will have larger pollen grains than species with shorter pistils, and that pistil length and pollen size will be positively correlated in a linear manner. To test this hypothesis, the relationship between pollen grain volume and pistil length was compared in 43 Asteraceae species from Argentina. A positive linear correlation was found between pollen volume and pistil length. This correlation remained significant even after potential effects of phylogenetic relatedness were removed. The maintenance of this correlation suggests that in Asteraceae the association between pistil length and pollen volume may reflect a functional rather than a phyletic relationship. In addition, the pistil length: pollen volume ratio (PPR) was analysed in relation to the phylogenetic position of the species. High values of PPR would imply a reduction of the male gametophyte in relation to the minimal volume that a pollen grain must have to grow and fertilise an ovule. Thus, the general pattern of pollen volume reduction in relation to pistil length previously found among many angiosperm families will be also present within a family, i.e., PPR values of derived Asteraceae would be higher than those of basal species. Results indicated that reduction of pollen volume in derived Asteraceae was three times greater than the concomitant shortening of pistil length. Consequently, PPR increased with the phylogenetic position of the taxa. This work supports the correlation between pistil and pollen characters previously found for other plant families and confirms the influence of post-pollination processes on pollen size evolution. Received: 4 November 1999 / Revision accepted: 14 February 2000     

Floral development in the androdioecious tree Tapiscia sinensis: Implications for the evolution to androdioecy

The evolutionary pathway between hermaphroditism and dioecy (females and males in a single population) draws widespread interests, and androdioecy (bisexuals and males in a single population) is rarely achieved as an intermediate state between the two breeding systems. Flower bud differentiations in the pistils of hermaphrodites and the pistillodes of males in androdioecious Tapiscia sinensis Oliv. are investigated by routine paraffin section technology, light microscopy, and scanning electron microscopy. A phylogenetic approach is used to analyze the origin of androdioecy. In T. sinensis, hermaphroditic flowers (HF) and male flowers (MF) experienced a similar development pattern in early flower bud differentiation, including the initiation of tepals and stamens. However, the carpel differentiation of MF and HF proceed in different patterns. In HF, the central zone bulges out and produces a ring meristem on which two to three carpel primordia emerge, which eventually developed into a normal pistil with a stigma, a style, and an ovary. However, in most MF, vestigial pistils are stem‐like (type I), and very few have an empty ovary (type II) or a sterile ovule (type III). Moreover, the evolution of sexual systems within the Huerteales indicates that hermaphroditism is the primitive character of T. sinensis. Tapiscia sinensis shows different degrees of reduction between male flowers and bisexual ones in the evolution to dioecy. Functional androdioecy originated from a hermaphroditic ancestor in T. sinensis and, as an intermediate sexual system, involves evolution from hermaphrodites to dioecy.     

Molecular cloning and characterization of cDNA encoding cardosin B,an aspartic proteinase accumulating extracellularly in the transmitting tissue of Cynara cardunculus L.

Cardosins A and B are related aspartic proteinases from the pistils of Cynara cardunculus L., whose milk-clotting activity has been exploited for the manufacture of cheese. Here we report the cloning of cardosin B cDNA and its organ, tissue and cytological localization. The cDNA-derived amino acid sequence has 73% similarity with that of cardosin A and displays several distinguishing features. Cardosin B mRNA was detected in young inflorescences but not in pistils of fully opened inflorescences, indicating that its expression is developmentally regulated. The proteinase, however, accumulates in the pistil until the later stages of floral development. Immunocytochemistry with a monospecific antibody localized cardosin B to the cell wall and extracellular matrix of the floral transmitting tissue. The location of cardosin B in the pistil is therefore clearly different from that of cardosin A, which was found at protein storage vacuoles of the stigmatic papillae and has been suggested to be involved in RGD-mediated proteolytic mechanisms. In view of these results the possible functions of cardosin B in the transmitting tissue are discussed.     

A Flower and Pod Staging System for Soybean

Flower and pod abscission limit soybean yield. A system forquantifying flower and pod development based on the morphologicalappearance of the flower prior to and following anthesis hasbeen developed to aid in studies of pod abscission. Changesin the appearance of the corolla, primarily the banner petal,are used to distinguish the different stages of the system.External pistil dimensions have been correlated with internalfeatures for each stage of development. From anthesis to podset, pistil length and weight increase almost two- and fivefold,respectively, and ovule development progresses from unfertilizedegg cells to embryos surrounded by cellular endosperm. Pod determinedare correlated with ovule length and width and embryo cell number.Flower and pod stages can be determined in situ, thus permittingnon-destructive observation and experimental manipulation offlowers or pods without necessarily impeding their development.Stages have been identified that indicate precisely when podset occurs and when young pods cease growing and ultimatelyabscise. This system of flower and pod staging is useful instudies designed to assess effects of abiotic or biotic stressand genetic factors on pod set and abortion. Abscission, anthesis, Glycine max (L.) Merr, embryo development, pod set     

Molecular analysis of a pistil-specific gene expressed in the stigma and stylar cortex of Solanum tuberosum

A gene, sts14, coding for a highly expressed mRNA in pistils of Solanum tuberosum, was isolated. Northern blot and in situ analyses demonstrated that the gene was expressed throughout pistil development in both the stylar cortex and the stigma. The deduced STS14 protein displays similarity to the pathogenesis-related PR-1 proteins. A possible function for protection or guidance of the pollen tubes through the pistil is discussed.     

Morphological and cytological development and starch accumulation in hermaphrodite and staminate flowers of olive (Olea europaea L.)

In olive (Olea europaea L.), the formation of functionally staminate flowers rather than fully functional hermaphrodites is one of the major factors limiting fruit set, as flowers with aborted pistils are incapable of producing fruit. Studies conducted on various angiosperm species have shown a correlation between flower abortion and starch content. Thus, it is important to know if starch content plays a role in regulating pistil development in olive and if so, what mechanism regulates starch distribution. Cyto-histological observations of staminate and hermaphrodite olive flowers show that pistil development in staminate flowers is interrupted after the differentiation of the megaspore mother cell. At that stage, starch grains were only detected in the ovary, style and stigma of the hermaphrodite flowers. No starch was observed in the pistils of the staminate flowers. This finding suggests a tight correlation between starch content and pistil development. The secondary origin of starch within the flower is indicated by low chlorophyll content in the gynoecium, undetectable Rubisco activity in the pistils of these two kinds of flowers and by the ultrastructure of the plastids observed by transmission electron microscope analysis. The plastids have few thylakoid membranes and grana and in the staminate flowers appeared very similar to proplastids. Considering differences in starch content between staminate and hermaphrodite flowers and the secondary origin of the starch, differences in pistil development in the staminate and hermaphrodite flowers could be related to differences in the sink strength of these two types of flowers.     

The differentiation and development of pistils of hermaphrodites and pistillodes of males in androdioecious Osmanthus fragrans L. and implications for the evolution to androdioecy

The evolutionary pathway between hermaphroditism and dioecy draws widespread interests, and androdioecy is rarely achieved as an intermediate state between the two breeding systems. Flower bud differentiations in the pistils of hermaphrodites and the pistillodes of males in androdioecious Osmanthus fragrans L. were investigated by paraffin sectioning to elucidate the evolution to androdioecy. Results showed that the regularity and rhythm in flower bud differentiation between males and hermaphrodites were almost consistent and included six main stages. However, the hermaphrodites always lagged behind the males at each stage. The apical floret in the same inflorescence developed earlier than did the lateral ones in both hermaphrodites and males. The most significant difference between males and hermaphrodites was observed at the carpel differentiation stage. Two carpel primordia appeared inside the stamens of both males and hermaphrodites at the initial stage. These two carpels gradually fused with each other in hermaphrodites and eventually developed into a normal pistil with a stigma, a style, and an ovary. However, a cavity grew conspicuously over time between two carpels as developed in males. The two carpels eventually developed into a pistillode with two independent bracteal tissues. However, from the whole development process, the male retained the developmental residue of the hermaphrodite. Thus, the pistillodes of males could be traced to the pistils of hermaphrodites. This finding shows that males may be derived from hermaphrodites in O. fragrans. On the basis of this finding and previous studies on Oleaceae, androdioecy could be regarded as a transition from hermaphroditism to dioecy in this family.     

The Relationship Between the Distribution of Periclinal Cell Divisions in the Shoot Apex and Leaf Initiation

Periclinal cell divisions in vegetative shoot apices of Pisumand Silene were recorded from serial thin sections by mappingall the periclinal cell walls formed less than one cell cyclepreviously. The distribution of periclinal divisions in theapical domes corresponded to the distributions subsequentlyoccurring in the apices when the young leaf primordia were forming.In Pisum, periclinal divisions were almost entirely absent fromthe I₁ region of the apical dome for half a plastochron justafter the formation of a leaf primordium and appeared, simultaneouslyover the whole of the next potential leaf site, about half aplastochron before the primordium formed. In Silene periclinaldivisions seemed to always present in the apical dome at thepotential leaf sites and also round the sides of the dome wherethe ensheathing leaf bases were to form. Periclinal divisionstherefore anticipated the formation of leaf primordia by occuring,in Pisum about one cell cycle and in Silene two or more cellcycles, before the change in the direction of growth or deformationof the surface associated with primordial initiation. Pisum, Silene, planes of cell division, orientation of cell walls, leaf primordia, shoot apical meristem, plastochron