Ovary,seed and fruit ofRutidea (Rubiaceae,Pavetteae)

The ovary ofRutidea is bicarpellate and incompletely bilocular (septum between locules not continuous). A solitary campylotropous ovule, ascending from a basal placenta, occurs in each locule. Based on their orientation and degree of curving, three ovule types are distinguished. As a consequence of the abortion of one ovule, the drupaceous fruits are one-seeded. The incomplete septum allows the spherical seed to fill out the entire interior of the fruit. The seeds are deeply ruminate (Spigelia type). They grow very fast, producing folds and undulations (ruminations) which invade and totally occupy the second locule, almost enveloping the aborted ovule. Comparisons with otherRubiaceae (especiallyPavetteae), show that hemianatropy and campylotropy occur more often in theRubiaceae than hitherto accepted. The study corroborates the close affinity betweenRutidea andNichallea.     

Development of the dimorphic anthers in Collomia grandiflora; evidence for heterochrony in the evolution of the cleistogamous anther

A modification characterizing all cleistogamous species is reduction in anther size of the CL (cleistogamous or closed) flower. In Collomia grandiflora the CL anther, in addition to being smaller, has only two locules; the CH (chasmogamous or open) flower anther has four locules. As a consequence, there is a modification in CL anther shape. From initially similar primordia, a divergence in histology between the two anther forms appears at archesporial cell differentiation when only two locules are established in the CL anther. The process of form divergence in the two anther types is examined in this study using histological, allometric, and 3-D computer graphic techniques. Allometric data from SEM images demonstrates the equivalence of primordial shapes at anther inception and divergence just prior to archesporial cell division, which signals the onset of sporogenous cell proliferation. Reconstructions of the anthers at archesporial cell division stage revealed differences in external and internal form and size, features unrelated to locule number. Fewer initial archesporial cells and a shorter duration of sporogenous cell proliferation in the CL anther correlates with a smaller anther with 1/10th the number of pollen grains at maturity. The CL anther shows less cell division activity from the time of archesporial cell division and no trace of the intercalary growth which appears during meiosis in the CH anther. The divergent CL anther size and form may be attributed to an earlier onset of abaxial locule differentiation in a smaller primordium which may itself preclude adaxial locule initiation. Heterochrony, or alteration in developmental timing, is proposed as the mode of evolution of the CL from the ancestral CH form.     

The Mechanics of the Grass Flower: Anther Dehiscence and Pollen Shedding in Maize

In this paper on the flower mechanics of the grasses, the openingmechanism of the maize anther is studied. Both the septum betweeneach two locules and the stomium of these porate-dehiscing anthersappear to be opened due to lysis of the middle lamellae of theircells. Additional mechanical force of the expanding pollen mightbe necessary to completely dissociate the parenchyma cells ofthe septum. A number of hours before anthesis the anther isstructurally able to dehisce. At anthesis the dehydrating endotheciumcells bend the locule walls bordering the pore in outward direction.Presumably evaporation is not the only cause for this dehydration. Poaceae; Zea mays ; flower; anther; dehiscence; endothecium; pollen     

S351┐1西瓜雄性不育的细胞学研究

西瓜Ｓ３５１－１雄性不育材料的细胞学观察表明：与对照的同系可育株相比,败育发生在次级造孢细胞到小孢子母细胞或小孢子四分体阶段,多数不育雄花花药中绒毡层始终未分化,药壁常由７－８层细胞组成,少数不育花药中出现绒毡层徒长现象;次级造孢细胞败育不同步,出现多核及多核仁现象,败育后期,药壁细胞逐渐解体,药室瓦解,花粉囊收缩变形。由此可见：其雄性不育与绒毡层的发育异常有直接联系。     

Mechanism of male sterility in Petunia: The relationship between pH,callase activity in the anthers,and the breakdown of the microsporogenesis

Summary In the locules of fertile Petunia hybrida anthers the in vivo pH during meiosis is 6.8–7.0 and no callase activity can be detected. Towards the end of the tetrad stage, the pH drops to 5.9–6.2 followed by a burst of callase activity. Subsequently, callose in the tetrad walls is digested and the quartets of microspores are released into the anther locules and develop into pollen grains. In the anther locules of one cytoplasmic male sterile (cms) Petunia type the pH drop and strong callase activity are already evident at early meiotic stages. Consequently, the callose already accumulated in the pollen mother cell (PMC) walls is digested and the PMC's cease to develop and are degraded. In another sterile genotype, the pH of the locule remains high (6.8–7.0), no callase activity is detected at the end of tetrad stage and the callose walls remain intact until a very late stage. It is suggested that the timing of callase activity is critical for the normal development of the male gametophyte and that faulty timing may result in male sterility. Measurements of pH in vivo and assays for callase activity in vitro indicate that the low pH is a precondition for the enzyme activity. Furthermore, it is suggested that the activation of callase in vivo is in some way connected with the changes in the pH of the locule.Contribution from The Volcani Institute of Agricultural Research, 1970 Series, No. 1709-E.Supported in part by grant No. FG-Is-171 from the United States Department of Agriculture, under P. L. 480.     

Increase in tomato locule number is controlled by two single-nucleotide polymorphisms located near WUSCHEL

In tomato (Solanum lycopersicum) fruit, the number of locules (cavities containing seeds that are derived from carpels) varies from two to up to 10 or more. Locule number affects fruit shape and size and is controlled by several quantitative trait loci (QTLs). The large majority of the phenotypic variation is explained by two of these QTLs, fasciated (fas) and locule number (lc), that interact epistatically with one another. FAS has been cloned, and mutations in the gene are described as key factors leading to the increase in fruit size in modern varieties. Here, we report the map-based cloning of lc. The lc QTL includes a 1,600-bp region that is located 1,080 bp from the 3' end of WUSCHEL, which encodes a homeodomain protein that regulates stem cell fate in plants. The molecular evolution of lc showed a reduction of diversity in cultivated accessions with the exception of two single-nucleotide polymorphisms. These two single-nucleotide polymorphisms were shown to be responsible for the increase in locule number. An evolutionary model of locule number is proposed herein, suggesting that the fas mutation appeared after the mutation in the lc locus to confer the extreme high-locule-number phenotype.     

Evaluating the genetic basis of multiple-locule fruit in a broad cross section of tomato cultivars

Lycopersicon esculentum accessions bearing fasciated (multiloculed) fruit were characterized based on their flower organ and locule number phenotypes. Greenhouse and field evaluations indicate that increases in locule number are associated with increases in the number of other floral organs (e.g., sepals, petals, stamens) in all stocks. F₁ complementation, F₂ segregation analysis, and genetic mapping indicate that at least four loci account for increases in the number of carpels/locules in these stocks. The most significant of these map to the bottoms of chromosomes 2 and 11 and correspond to the locule number and fasciated loci. All stocks tested were fixed for mutations at the fasciated locus, which maps to the 0.5-cM interval between the markers T302 and cLET24J2A and occurs in at least three allelic forms (wild type and two mutants). One of the fasciated mutant alleles is associated with nonfused carpels and repressed recombination and may be due to a small inversion or deletion. The other two loci controlling locule number correspond to the lcn1.1 and lcn2.2 loci located on chromosomes 1 and 2, respectively.     

Development of the pollen grain and tapetum of wheat (Triticum aestivum) in untreated plants and plants treated with chemical hybridizing agent RH0007

Summary A study of pollen development in wheat was made using transmission electron microscopy (TEM). Microspores contain undifferentiated plastids and mitochondria that are dividing. Vacuolation occurs, probably due to the coalescence of small vacuoles budded off the endoplasmic reticulum (ER). As the pollen grain is formed and matures, the ER becomes distended with deposits of granular storage material. Mitochondria proliferate and become filled with cristae. Similarly, plastids divide and accumulate starch. The exine wall is deposited at a rapid rate throughout development, and the precursors appear to be synthesized in the tapetum. Tapetal cells become binucleate during the meiosis stage, and Ubisch bodies form on the plasma membrane surface that faces the locule. Tapetal plastids become surrounded by an electron-translucent halo. Rough ER is associated with the halo around the plastids and with the plasma membrane. We hypothesize that the sporopollenin precursors for both the Ubisch bodies and exine pollen wall are synthesized in the tapetal plastids and are transported to the tapetal cell surface via the ER. The microspore plastids appear to be involved in activities other than precursor synthesis: plastid proliferation in young microspores, and starch synthesis later in development. Plants treated with the chemical hybridizing agent RH0007 show a pattern of development similar to that shown by untreated control plants through the meiosis stage. In the young microspore stage the exine wall is deposited irregularly and is thinner than that of control plants. In many cases the microspores are seen to have wavy contours. With the onset of vacuolation, microspores become plasmolyzed and abort. The tapetal cells in RH0007-treated locules divide normally through the meiosis stage. Less sporopollenin is deposited in the Ubisch bodies, and the pattern is less regular than that of the control. In many cases, the tapetal cells expand into the locule. At the base of one of the locules treated with a dosage of RH0007 that causes 95% male sterility, several microspores survived and developed into pollen grains that were sterile. The conditions at the base of the locule may have reduced the osmotic stress on the microspores, allowing them to survive. Preliminary work showed that the extractable quantity of carotenoids in RHOOO7-treated anthers was slightly greater than in controls. We concluded that RH0007 appears to interfere with the polymerization of carotenoid precursors into the exine wall and Ubisch bodies, rather than interfering with the synthesis of the precursors.     

Identification of asymmetrically winged samaras from the Western Hemisphere

A key is presented for use in identifying asymmetrically winged fruits (samaras) with either proximal or distal locules. It aids identification based on dispersed fuit morphology and can be used to identify undetermined extant herbarium specimens or fossil fruits to the correct extant family and genus. The 39 genera from 11 families (Aceraceae, Anacardiaceae, Fabaceae, Malpighiaceae, Phytolaccaceae, Polygalaceae, Polygonaceae, Rutaceae, Sapindaceae, Trigoniaceae, Ulmaceae) are distinguished on the basis of wing venation, size of fruit, presence and position of attachment surface, presence and type of subsidiary wings on the ovary wall. ornamentation, size and shape of the ovary, locule position, shape of locule cross section, style position and ornamentation, distinction between ovary wall and wing, and angle of attachment between individual samaras. The developmental origins of some of these features are discussed.     

Direct interaction of FtsZ and MreB is required for septum synthesis and cell division in Escherichia coli

How bacteria coordinate cell growth with division is not well understood. Bacterial cell elongation is controlled by actin–MreB while cell division is governed by tubulin–FtsZ. A ring‐like structure containing FtsZ (the Z ring) at mid‐cell attracts other cell division proteins to form the divisome, an essential protein assembly required for septum synthesis and cell separation. The Z ring exists at mid‐cell during a major part of the cell cycle without contracting. Here, we show that MreB and FtsZ of Escherichia coli interact directly and that this interaction is required for Z ring contraction. We further show that the MreB–FtsZ interaction is required for transfer of cell‐wall biosynthetic enzymes from the lateral to the mature divisome, allowing cells to synthesise the septum. Our observations show that bacterial cell division is coupled to cell elongation via a direct and essential interaction between FtsZ and MreB.     

Infertile seeds ofYucca schottii: A beneficial role for the plant in the yucca-yucca moth mutualism?

Summary The yucca-yucca moth interaction is a classic case of obligate mutualism. Female moths pollinate and oviposit in the gynoecium of the flower; however, maturing larvae eat a fraction of the developing seeds. We studied within-fruit distributions of four seed types (fertile, infertile, eaten and uneaten seeds) in order to evaluate costs and benefits in aYucca schottii population in southeastern Arizona. We focused on how the spatial arrangement of seeds affected larval behaviour and, hence, the costs of the mutualism to the yucca. Infertile seeds were distributed throughout both infested and uninfested locules. Additionally, moth larvae feeding in a single locule preferred fertile seeds and even avoided infertile seeds and left the fruit significantly more often when they encountered infertile seeds. We suggest that, regardless of the cause of infertile seeds, they function as blocking units within seed locules and therefore reduce seed predation by moth larvae. We also suggest that, together with certain other fruit traits, the presence of infertile seeds promotes the evolutionary stability of this pollination mutualism.     

Is the quantity of orbicules released by Dactylis glomerata and Cynosurus echinatus (Poaceae) big enough to play an allergenic role?

Orbicule characteristics of Dactylis glomerata and Cynosurus echinatus (Poaceae) were investigated using light (LM), scanning electron (SEM) and transmission electron microscopy (TEM). Based on SEM micrographs, the number of orbicules per 100?µm² of the locule wall surface was determined in both dehisced and undehisced anthers and was further compared statistically. A total of 100 pollen grains were examined using SEM in search for orbicules attached to the pollen exine. Orbicules were not found distributed freely in the anther locules. They were attached to the locule wall surface through sporopolleninous fibrils, the orbicule wall being firmly embedded in, and often in continuity with the thin layer of sporopollenin lining each locule. The orbicule density on the locule wall surface of both the dehisced and undehisced anthers did not differ significantly. Only a few orbicules were seen attached to the pollen exine in both species. It is concluded that orbicules are not easily removed from the surface of the locule wall and, consequently, that the number of orbicules emitted from the two grass species is too low to play a significant role in triggering allergic diseases.     

Abnormal anther development and high sporopollenin synthesis in benzotriazole treated male sterile Helianthus annuus L

Foliar application of 1.5% benzotriazole induced 100% pollen sterility in H. annuus. Pollen abortion in treated plants was mainly associated with abnormal behaviour of tapetum. A limited number of anther locule showed early degeneration of tapetum followed by disintegration of sporogenous tissues. On the other hand, some locules showed normal development of tapetum at initial stages. However, this tapetum exhibited degenerated and non-functional cell organelles. In both these situations tapetum failed to provide proper nourishment to developing microspores. The ultrastructure of both tapetum and microspores is different from that of control material with irregularities of exine deposition, endopolyploidy of tapetal nuclei and an alteration of organelle composition being correlated with sterility. Pollen grains thus developed were devoid of nucleus and cell organelles and were complete sterile.     

Differential Expression of Two Endo-1,4-[beta]-Glucanase Genes in Pericarp and Locules of Wild-Type and Mutant Tomato Fruit

The mRNA accumulation of two endo-1,4-[beta]-D-glucanase genes, Cel1 and Cel2, was examined in the pericarp and locules throughout the development of normal tomato (Lycopersicon esculentum) fruit and the ripening-impaired mutants rin and Nr. Both Cel1 and Cel2 were expressed transiently at the earliest stages of fruit development during a period corresponding to cell division and early cell expansion. In the pericarp, the mRNA abundance of both genes increased markedly at the breaker stage; the level of Cel1 mRNA decreased later in ripening, and that of Cel2 increased progressively. Cel2 mRNA levels also increased at the breaker stage in locules but after initial locule liquefaction was already complete. In rin fruit mRNA abundance of Cel1 was reduced and Cel2 was virtually absent, whereas in Nr Cel1 was expressed at wild-type levels and Cel2 was reduced. In wild-type fruit ethylene treatment slightly promoted the mRNA accumulation of both genes. In rin fruit ethylene treatment strongly increased the mRNA abundance of Cel1 to an extent greater than in wild-type fruit, but Cel2 mRNA was absent even after ethylene treatment. These two endo-1,4-[beta]-D-glucanase genes, therefore, do not show coordinated expression during fruit development and are subject to distinct regulatory control. These results suggest that the product of the Cel2 gene contributes to ripening-associated cell-wall changes.     

Carbohydrate solutilization of tomato locule tissue cell walls: Parallels with locule tissue liquefaction during ripening

Carbohydrate solubilization and glycosidase activities were investigated in tomato ( Lycopersicon esculentum Mill. cv. Solar Set) locule cell walls to identity processes involved in the liquefaction of this tissue. Cell walls were prepared from the locule tissue of fruit at the immature green, mature green, and breaker stages of development. Enzymically active walls incubated in dilute buffer released high molecular mass pectins, oligomeric carbohydrate, and the neutral sugars rhamnose, glucose, galactose, arabinose, xylose, and mannose. The release was sustained for at least 50 h at 34°C and was inhibited more than 50% by 1 m M Hg²⁺. Pectins released from the cell walls of locule tissue at progressive stages of liquefaction were similar in molecular mass and showed no evidence of downshifts on a Sepharose CL–2B–300 column during prolonged incubation. A cell-free protein extract prepared from the locule tissue of mature-green fruit promoted a net release of polymeric and monomeric carbohydrates from high-temperature inactivated cell walls. Polygalacturonase activity was not detected in locule protein although glycosidases including β-mannosidase (EC 3.2.1.25), α- and β-galactosidases (EC 3.2.1.22–23), β-arabinosidase (EC 3.2.1.56) and β-glucosidase (EC 3.2.1.21) were present. Pectinmethylesterase (EC 3.1.1.1 1) activity was detected at the immature-green stage but declined to negligible levels in mature-green and breaker locule tissue. Parallels between the in vitro solubilization of carbohydrate from locule tissue cell walls and the changes occurring during locule liquefaction are discussed.     

Endoconidiogenesis in Endoconidioma populi and Phaeotheca fissurella

Details of the development of endoconidia were basically the same in Endoconidioma populi and Phaeotheca fissurella. In both species, endoconidiogenesis involved (i) subdivision of conidiogenous mother cells by septation to form two to several daughter cells; (ii) accumulation of an electron-dense material between the daughter and mother cell walls; and (iii) separation of the daughter cells by septum schizolysis, accompanied by the dissolution of mother cell wall. Conidiomata of E. populi were unique in having a closed peridium and a locule filled with conidiogenous mother cells and, therefore, we proposed the new term, cleistopycnidium (pl. -a), for this structure. In the cleistopycnidium of E. populi, endoconidiation usually began in the core of the locule and spread outward. Release of endoconidia was by the degeneration of peridial cell walls.