Histochemical Localization of Essential Oils and Bioactive Substances in the Seed Coat of the Halophyte <Emphasis Type="Italic">Crithmum maritimum</Emphasis> L. (Apiaceae)

Despite seeds and fruits of several halophytes being rich in essential oils and other bioactive substances, the histochemical characterization of these compounds has not received much attention. The aims of the present investigation were to localize the essential oils and the bioactive substances in the seed coat of the oilseed halophyte Crithmum maritimum L. Fruits were collected from the rocky coasts of Tabarka (NW of Tunisia, 36°57′12″ N, 08°45′18″ E). C. maritimum L. seed is shown to be surrounded by two envelopes: The first structure is a secretory envelope, consisting in about 20 canals. The second layer represents the endocarp. As revealed by fluorescence and light microscopy, the essential oils, O-dihydroxyphenols and flavonoids, known as bioactive compounds, were accumulated in the canals. The endocarp layer accumulated polysaccharides, O-dihydroxyphenols, and flavonoids. As a whole, these findings highlight the histochemical features and confirm the valuable quality of C. maritimum L. seeds.     

Ovule,fruit and seed development in Abolboda (Xyridaceae,Poales): implications for taxonomy and phylogeny

Xyridaceae belongs to the xyrid clade of Poales, but the phylogenetic position of the xyrid families is only weakly supported. Xyridaceae is divided into two subfamilies and five genera, the relationships of which remain unclear. The development of the ovule, fruit and seed of Abolboda spp. was studied to identify characteristics of taxonomic and phylogenetic value. All of the studied species share anatropous, tenuinucellate and bitegmic ovules with a micropyle formed by the inner and outer integuments, megagametophyte development of the Polygonum type, seeds with a tanniferous hypostase, a helobial and starchy endosperm and an undifferentiated embryo, seed coat derived from both integuments with a tanniferous tegmen and a micropylar operculum, and fruits with a parenchymatous endocarp and mesocarp and a sclerenchymatous exocarp. Most of the ovule and seed characteristics described for Abolboda are also present in Xyris and may represent a pattern for the family. Abolboda is distinguished by the ovule type, endosperm formation and the number of layers in the seed coat, in agreement with its classification in Abolbodoideae. The following characteristics link Xyridaceae to Eriocaulaceae and Mayacaceae, supporting the xyrid clade: tenuinucellate, bitegmic ovules; seeds with a tanniferous hypostase, a starchy endosperm and an undifferentiated embryo; and a seed coat with a tanniferous tegmen. A micropylar operculum in the seeds of Abolboda is described for the first time here and may represent a synapomorphy for the xyrids. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175 , 144–154.     

Development of ovule,fruit and seed of Xyris (Xyridaceae,Poales) and taxonomic considerations

The development of the ovule, fruit and seed of Xyris spp. was studied to assess the embryological characteristics of potential taxonomic usefulness. All of the studied species have (1) orthotropous, bitegmic and tenuinucellate ovules, with a micropyle formed by both the endostoma and exostoma; (2) a cuticle in the ovules and seeds between the nucellus/endosperm and the inner integument and between the inner and outer integuments; (3) helobial, starchy endosperm; (4) a reduced, campanulate and undifferentiated embryo; (5) a seed coat formed by a tanniferous endotegmen, endotesta with thick‐walled cells and exotesta with thin‐walled cells; and (6) a micropylar operculum formed from inner and outer integuments. The pericarp is composed of a mesocarp with cells containing starch grains and an endocarp and exocarp formed by cells with U‐shaped thickened walls. The studied species differ in the embryo sac development, which can be of the Polygonum or Allium type, and in the pericarp, which can have larger cells in either endocarp or exocarp. The Allium‐type embryo sac development was observed only in Xyris spp. within Xyridaceae. Xyris also differs from the other genera of Xyridaceae by the presence of orthotropous ovules and a seed coat formed by endotegmen, endotesta and exotesta, in agreement with the division of the family into Xyridoideae and Abolbodoideae. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177 , 619–628.     

桃儿七种子休眠解除过程中细胞壁代谢及种皮超微结构的变化北大核心CSCD

为探究低温层积过程中桃儿七种子细胞壁代谢及种皮超微结构与休眠解除的内在联系,该研究通过低温层积解除桃儿七种子休眠,分析休眠解除过程中种子不同部位细胞壁组分及相关代谢酶的变化,同时利用扫描电镜对种皮的超微结构进行观察。结果表明,(1)桃儿七种皮主要由角质层、栅状石细胞层及海绵组织层3层构成,在层积过程中,种皮内部的海绵组织逐步疏松膨胀,种皮表面破损加剧;(2)种子不同部位的细胞壁组分具有明显差异,整个层积过程中,种胚、种皮和胚乳中的纤维素含量均在层积中期(45 d和60 d)降至最低,3个部位的纤维素酶活性在层积中期对应升高;种胚和种皮内的半纤维素含量均在层积中期显著下降,种皮中甘露聚糖酶活性和木糖苷酶活性在层积中期时相应达到最大;3个部位的果胶含量均在层积后期(75 d和90 d)时显著下降,而种皮和胚乳中多聚半乳糖醛缩酶活性也在层积后期相应升高;(3)种胚和胚乳内过氧化物酶活性在层积75 d和90 d时明显下降,而SOD活性在此时显著上升。(4)种子不同部位3种木质素单体的组成比例具有明显区别,同时3种木质素单体含量均随层积时间的延长而显著降低,且胚乳和种皮中的S-木质素含量对种子萌发存在显著的负向影响关系。研究认为,在低温层积过程中,桃儿七种子内细胞壁组分纤维素、半纤维素及木质素的逐步酶解,活性氧作用下的细胞壁松弛以及海绵组织层的疏松膨胀和种皮的破裂,破坏了细胞壁的刚性结构,促使种子机械束缚力降低,吸水性能提高、胚根生长能力增强,最终导致其休眠解除。     

Effects of APETALA2 on embryo, endosperm, and seed coat development determine seed size in Arabidopsis

Arabidopsis APETALA2 (AP2) controls seed mass maternally, with ap2 mutants producing larger seeds than wild type. Here, we show that AP2 influences development of the three major seed compartments: embryo, endosperm, and seed coat. AP2 appears to have a significant effect on endosperm development. ap2 mutant seeds undergo an extended period of rapid endosperm growth early in development relative to wild type. This early expanded growth period in ap2 seeds is associated with delayed endosperm cellularization and overgrowth of the endosperm central vacuole. The subsequent period of moderate endosperm growth is also extended in ap2 seeds largely due to persistent cell divisions at the endosperm periphery. The effect of AP2 on endosperm development is mediated by different mechanisms than parent-of-origin effects on seed size observed in interploidy crosses. Seed coat development is affected; integument cells of ap2 mutants are more elongated than wild type. We conclude that endosperm overgrowth and/or integument cell elongation create a larger postfertilization embryo sac into which the ap2 embryo can grow. Morphological development of the embryo is initially delayed in ap2 compared with wild-type seeds, but ap2 embryos become larger than wild type after the bent-cotyledon stage of development. ap2 embryos are able to fill the enlarged postfertilization embryo sac, because they undergo extended periods of cell proliferation and seed filling. We discuss potential mechanisms by which maternally acting AP2 influences development of the zygotic embryo and endosperm to repress seed size.     

Dichilanthe, an unusual Asiatic Rubiaceae with "Lonicera flowers" and "dipterocarp fruits"

Dichilanthe, a disjunctly distributed, arborescent Southeast Asiatic genus (D. zeylanica: Sri Lanka; D. borneensis: West Borneo) with collar-like, persistent stipules, has strongly zygomorphic, ornithophilous flowers which show secondary pollen presentation. The curved corolla is two-lipped. The upper lip consists of 2, and the lower lip of 3 fused corolla lobes. The calyx, too, is zygomorphic. The curved, exserted style ends in a swollen “stylar head' which apically bears two small stigmatic (receptive) areas in a zygomorphic arrangement. The flowers are borne in compact, terminal heads, held together by enlarged stipules of a bract-pair immediately below the inflorescence. The dispersal units (diaspores) mimic dipterocarp fruits. They consist of a persistent, wing-like pair of bracts whose±cuplike stipules enclose the fruits. The diaspores break off at the node immediately below the bract-pair, where there is a distinct abscission zone. Initial on”primary“dispersal by wind may be followed by facultative”secondary“dispersal by floating in water.”Pith tissue“produced by each fruit of the diaspore, and the air spaces contained therein, are likely to be adaptations to floating. This”pith tissue“, a loose, parenchymatic,± irregularly arranged area of the fruit wall which partially disintegrates during fruit maturation, represents a modified portion of the endocarp; the remainder of the endocarp is”normal“sclerenchymatic tissue coating the two locules. The initial stages of this endocarp differentiation are already observable in early developmental stages, i.e., in ovaries of flower buds and open flowers. The bicarpellate ovaries contain a solitary, anatropous pendulous ovule per locule. Viable seeds have large embryos and only c. 5–6 layers of oily endosperm; their exotesta cells have delicate, ring-like thickenings. In developing fruits of individual inflorescences, a high frequency of seed abortion was noted. Not uncommonly, there is only a single viable seed per dispersal unit, i.e., only a solitary seedling emerging from a diaspore. Germination of the seeds is cryptocotylar. The pollen of D. zeylanica is suboblate and 5- or 6-colpate (with the colpi being rather short); the exine is finely reticulate. In spite of several of its character states being unusual and aberrant, the tribal position of Dichilanthe in the Guettardeae is not questioned, although it is concluded that the genus occupies a rather isolated position in the tribe.     

Suppression of sucrose synthase gene expression represses cotton fiber cell initiation,elongation, and seed development

Cotton is the most important textile crop as a result of its long cellulose-enriched mature fibers. These single-celled hairs initiate at anthesis from the ovule epidermis. To date, genes proven to be critical for fiber development have not been identified. Here, we examined the role of the sucrose synthase gene (Sus) in cotton fiber and seed by transforming cotton with Sus suppression constructs. We focused our analysis on 0 to 3 days after anthesis (DAA) for early fiber development and 25 DAA, when the fiber and seed are maximal in size. Suppression of Sus activity by 70% or more in the ovule epidermis led to a fiberless phenotype. The fiber initials in those ovules were fewer and shrunken or collapsed. The level of Sus suppression correlated strongly with the degree of inhibition of fiber initiation and elongation, probably as a result of the reduction of hexoses. By 25 DAA, a portion of the seeds in the fruit showed Sus suppression only in the seed coat fibers and transfer cells but not in the endosperm and embryo. These transgenic seeds were identical to wild-type seeds except for much reduced fiber growth. However, the remaining seeds in the fruit showed Sus suppression both in the seed coat and in the endosperm and embryo. These seeds were shrunken with loss of the transfer cells and were <5% of wild-type seed weight. These results demonstrate that Sus plays a rate-limiting role in the initiation and elongation of the single-celled fibers. These analyses also show that suppression of Sus only in the maternal seed tissue represses fiber development without affecting embryo development and seed size. Additional suppression in the endosperm and embryo inhibits their own development, which blocks the formation of adjacent seed coat transfer cells and arrests seed development entirely.     

Water Relations of Seed Development and Germination in Muskmelon (Cucumis melo L.) : IV. Characteristics of the Perisperm during Seed Development

We previously reported that an apparent water potential disequilibrium is maintained late in muskmelon (Cucumis melo L.) seed development between the embryo and the surrounding fruit tissue (mesocarp). To further investigate the basis of this phenomenon, the permeability characteristics of the tissues surrounding muskmelon embryos (the mucilaginous endocarp, the testa, a 2- to 4-cell-layered perisperm and a single cell layer of endosperm) were examined from 20 to 65 days after anthesis (DAA). Water passes readily through the perisperm envelope (endosperm + perisperm), testa, and endocarp at all stages of development. Electrolyte leakage (conductivity of imbibition solutions) of individual intact seeds, decoated seeds (testa removed), and embryos (testa and perisperm envelope removed) was measured during imbibition of freshly harvested seeds. The testa accounted for up to 80% of the total electrolyte leakage. Leakage from decoated seeds fell by 8- to 10-fold between 25 and 45 DAA. Presence of the perisperm envelope prior to 40 DAA had little effect on leakage, while in more mature seeds, it reduced leakage by 2- to 3-fold. In mature seeds, freezing, soaking in methanol, autoclaving, accelerated aging, and other treatments which killed the embryos had little effect on leakage of intact or decoated seeds, but caused osmotic swelling of the perisperm envelope due to the leakage of solutes from the embryo into the space between the embryo and perisperm. The semipermeability of the perisperm envelope of mature seeds did not depend upon cellular viability or lipid membrane integrity. After maximum seed dry weight is attained (35-40 DAA), the perisperm envelope prevents the diffusion of solutes, but not of water, between the embryo and the surrounding testa, endocarp, and mesocarp tissue.     

DEVELOPMENT OF NORMAL AND SEEDLESS ACHENES IN CICHORIUM INTYBUS (COMPOSITAE)

Cross- and partially cross-pollinated capitula of Cichorium intybus (Compositae, Lactuceae) were examined for a study of normal and seedless fruit development respectively. Embryos develop according to the Asterad pattern, and the free-nuclear endosperm becomes cellular 15–17 hrs after pollination. A zone of disorganized cellular material surrounds the embryo sac at anthesis, and, in normal achenes, this zone expands as the seed develops. Initially the developing seed elongates and comes into contact with the top of the ovary by 48 hrs. In contrast to this pattern, the ovule in developing seedless achenes degenerates within 72 hrs. Irregularities, such as an abnormally proliferating endothelium, embryo formation without endosperm, and endosperm formation without an embryo often accompany this degeneration. Differentiation of the pericarp in seeded achenes begins between 48 and 72 hrs, starting at the apex and proceeding basipetally; in seedless fruits the process is similar though initiated somewhat later. The normal pericarp at maturity exhibits a pigmented exocarp, a broad mesocarp of thick-walled lignified cells, and a tenuous endocarp. In seedless achenes the fruit coat is similar except that the exocarp is colorless and the cells of the mesocarp are relatively small.     

赤霉素对紫斑牡丹种子下胚轴萌发及其种皮和胚乳结构的影响

以紫斑牡丹种子为试验材料,考察不同浓度赤霉素(GA_3)处理下种子生根情况,同时对其种皮纹饰进行了扫描电镜(SEM)观察,并对胚乳结构进行了荧光倒置显微镜、透射电镜(TEM)观察,以揭示GA_3对紫斑牡丹种子下胚轴解除休眠过程中种子种皮、胚乳结构变化和生根的影响。结果表明:(1)GA_3处理能够促进紫斑牡丹种子生根,以300 mg/L GA_3处理的种子生根效果最好,与对照相比可提前14.66 d生根,生根率可达62.33%。(2)扫描电镜观察发现,紫斑牡丹种皮表面含有蜡质,种子萌发进程中蜡质明显不断增加,种皮表面网眼逐渐消失,种皮皱缩明显。(3)光学显微镜观察发现,GA_3处理的紫斑牡丹种子胚乳细胞中含有较多淀粉体和蛋白体,并随着种子萌发进程逐渐积累,可为种子萌发提供足够的养分。(4)透射电镜观察发现,GA_3处理的紫斑牡丹种子胚乳细胞内大分子营养物质不断降解,线粒体、内质网、高尔基体等细胞器相继出现,种子下胚轴休眠解除,细胞壁较薄后期消融,利于营养物质传送。研究认为,适宜浓度GA_3处理可有效加快紫斑牡丹种皮结构的改变和胚乳细胞内物质代谢进程,促进种子萌发,且300 mg/L GA_3处理紫斑牡丹种子24 h可以获得最好的生根效果。     

Comparative morphology and physiology of fruit and seed development in the two shrubs Rhus aromatica and R. glabra (Anacardiaceae)

Morphology and physiology of fruit and seed development were compared in Rhus aromatica and R. glabra (Anacardiaceae), both of which produce drupes with water-impermeable endocarps. Phenology of flowering/fruiting of the two species at the study site was separated by ∼2 mo. However, they were similar in the timetable and pattern of fruit and seed development; it took ∼2 mo and ∼1.5 mo for flowers of Rhus aromatica and R. glabra, respectively, to develop into mature drupes. The single sigmoidal growth curve for increase in fruit size and in dry mass of these two species differs from the double-sigmoidal one described for typical commercial drupes such as peach and plum. Order of attainment of maximum size was fruit and endocarp (same time), seed coat, and embryo. By the time fruits turned red, the embryo had reached full size and become germinable; moisture content of seed plus endocarp had decreased to ∼40%. The endocarp was the last fruit component to reach physiological maturity, which coincided with development of its impermeability and a seed plus endocarp moisture content of <10%. At this time, ∼50, 37, and 13% of the dry mass of the drupe was allocated to the exocarp plus mesocarp unit, endocarp, and seed, respectively. The time course of fruit and seed development in these two species is much faster than that reported for other Anacardiaceae, including Rhus lancea, Protorhus, and Pistacia.     

An unusual case of epigeal cryptocotylar germination in Rollinia salicifolia (Annonaceae)

An unusual case of epigeal cryptocotylar germination found in Rollinia salicifolia Schltdl. (Annonaceae) is described and is discussed in relation to the terminology used for germination studies. The terms cryptocotylar and phanerocotylar are used to describe the permanence of cotyledons within the seed coat or endocarp; the terms epigeal and hypogeal are used to refer the position of cotyledons in relation to ground level. The terms to describe position about ground level and permanence of cotyledons within the seed coat or endocarp are not used simultaneously in many papers, and some authors consider the terms cryptocotylar and hypogeal to be synonyms. Cases of epigeal cryptocotylar germination seem to be scarce in the literature. The morphological characters shown by R. salicifolia seeds and seedlings − a non-chlorophyllous embryo, abundant endosperm, thick woody seed coat, thickened hypocotyl and non-photosynthetic haustorial cotyledons − are closely related to its epigeal cryptocotylar germination. This is the first record of this type of germination in Argentina.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 53–56.     

Systemic Invasion of Plum Seed and Fruit by Xanthomonas campestris pv. pruni through Stalks

Many fruits on Golden King plum trees inoculated through the stalks with Xanthomonas campestris pv. pruni developed unusual lesions extending from the exocarp to the endocarp. A few uninoculated, diseased fruits had similar lesions. The pathogen was isolated from both inoculated and uninoculated stalks and from seeds inside fruits. Scanning electron microscopy of inoculated stalks and mature fruits with unusual lesions revealed that vascular channels of the stalk, seed coat, stony endo, carp, and mesocarp were filled with masses of X. campestris pv. pruni. Bacterial colonies also occurred in other tissues of these fruit parts but were apparently absent from the starchy endosperm or surface of the diseased exocarp. This is the first full report of systemic movement of X. campestris pv. pruni to seed and fruit through stalks.     

ELEMENTAL DISTRIBUTION IN SEEDS OF THE HALOPHYTES SALICORNIA PACIFICA VAR. UTAHENSIS AND ATRIPLEX CANESCENS

Little information is available on the distribution of ions in seeds of halophytes. Seeds of two halophytes, Salicornia pacifica var. utahensis (Tidestrom) Munz, a desert salt playa type, and Atriplex canescens (Pursh) Nutt., a desert shrub, were analyzed by energy dispersive X-ray microanalysis. The relative ion concentration in three regions, the seed coat, endosperm, and embryo, were determined. The total relative concentration of elements was higher in seeds of S. pacifica var. utahensis as compared to A. canescens. The seed coats of S. pacifica var. utahensis contained the highest counts of sodium, chlorine, potassium, and calcium, whereas the embryo and endorsperm were both high in phosophorus. In A. canescens, sodium and chlorine were very low in all three tissues. The embryo contained the major amount of phosphorus, although potassium was high in both the seed coat and the embryo. These results support the concept of ion compartmentalization in the seeds of these two halophytes.     

Developmental anatomy and morphology of the ovule and seed of heliconia (heliconiaceae, zingiberales)

The developmental anatomy and morphology of the ovule and seed in several species of Heliconia were investigated as part of an embryological study of the Heliconiaceae and to provide a better understanding of their relationships with the other families of the Zingiberales. Heliconia species have an ovule primordium with an outer integument of both dermal and subdermal origin. The archesporial cell is divided into a megasporocyte and a single parietal cell, which in turn are divided only anticlinally to form a single parietal layer, disintegrating later during gametogenesis. The embryo sac was fully developed prior to anthesis. In the developing seed, the endosperm was nuclear, with wall formation in the globular stage; a nucellar pad was observed during embryo development, but later became compressed. The ripe fruit contained seeds enveloped by a lignified endocarp that formed the pyrenes, with each pyrene having an operculum at the basal end; the embryo was considered to be differentiated. Most of these characteristics are shared with other Zingiberales, although the derivation of the operculum from the funicle and the formation of the main mechanical layer by the endocarp are unique to the Heliconiaceae.     

The Morphology and Anatomy of Ovule and Fruit Development in Arachis hypogaea L

The vascular system of the monocarpellary gynoecium with tenwell differentiated traces and a few cross links probably representsa precocious development of the post-fertilization vasculatureof the fruit wall. The restriction of the two integuments ofthe ovule to the micropylar half, and the endothecial natureof the chalazal cells adjoining the embryo sac appear to indicatea pathway of derivation of the unitegmic tenumucellate ovulefrom the bitegmic crassinucellate one. During double fertilization,a dark staining refractive body appears in the nucleolus ofthe egg as well as the fusion product of the polar nuclei. The peg that carries the ovary into the soil after fertilizationgrows by the activity of a rib meristem at the basal solid partof the gynoecium. During sub-soil fruit development, the ovarywall develops a prominent spongy inner zone which finally disappears,and a peripheral zone that forms the mature fruit wall. Theabinitio nuclear endosperm is much reduced and degenerates afterproducing a few cell layers in the chalazal half alone. Seeddevelopment is pachychalazal. The main vascular supply of theseed branches at the chalaza into eight to ten strands in theseed coat. All seeds that have a vascular ramification in theseed coat are probably pachychalazal. In the variety Valencia, diminutive fruits with viable seedmay develop aerially from pegs that fail to grow long enoughto reach the soil from the higher nodes. Arachis hypogaea L., groundnut, fruit development, seed development, carpel vasculature, seed vasculature, pachychalaza     

Endocarp thickness affects seed removal speed by small rodents in a warm-temperate broad-leafed deciduous forest, China

Seed traits are important factors affecting seed predation by rodents and thereby the success of recruitment. Seeds of many tree species have hard hulls. These are thought to confer mechanical protection, but the effect of endocarp thickness on seed predation by rodents has not been well investigated. Wild apricot (Prunus armeniaca), wild peach (Amygdalus davidiana), cultivated walnut (Juglans regia), wild walnut (Juglans mandshurica Maxim) and Liaodong oak (Quercus liaotungensis) are very common tree species in northwestern Beijing city, China. Their seeds vary greatly in size, endocarp thickness, caloric value and tannin content. This paper aims to study the effects of seed traits on seed removal speed of these five tree species by small rodents in a temperate deciduous forest, with emphasis on the effect of endocarp thickness. The results indicated that speed of removal of seeds released at stations in the field decreased significantly with increasing endocarp thickness. We found no significant correlations between seed removal speed and other seed traits such as seed size, caloric value and tannin content. In seed selection experiments in small cages, Père David's rock squirrel (Sciurotamias davidianus), a large-bodied, strong-jawed rodent, selected all of the five seed species, and the selection order among the five seed species was determined by endocarp thickness and the ratio of endocarp mass/seed mass. In contrast, the Korean field mouse (Apodemus peninsulae) and Chinese white-bellied rat (Niviventer confucianus), with relatively small bodies and weak jaws, preferred to select small seeds like acorns of Q. liaotungensis and seeds of P. armeniaca, indicating that rodent body size is also an important factor affecting food selection based on seed size. These results suggest endocarp thickness significantly reduces seed removal speed by rodents and then negatively affects dispersal fitness of seeds before seed removal of tree species in the study region. However, effect of endocarp thickness on final dispersal fitness needs further investigation because it may increase seed caching and survival after seed removal.     

Growth Substances Separated from the Fruits of Cassia fistula

The growth substances of the seeds of Cassia fistula were studied and the changes in the relative levels in the endosperm and embryo (plus cotyledons) with development of the seed were noted. Indoleacetic acid was found to be the major auxin component of the seed almost throughout its growth and development, while acidic inhibitors possibly belonging to β-complex were also noted in bioassay tests. The main source of the IAA in the seed is the endosperm, although measurable amounts are also present in the embryo. While this IAA activity in the endosperm is detectable till maturity of the fruit, it decreases relatively in the embryo to fall to insignificance at maturity of the seed. However, there is indication of the binding of such IAA in the embryo or the cotyledon, which can be released by alkaline hydrolysis but not before the seeds are matured. No such bound auxin could be detected in the endosperm. The inhibitors, on the other hand, are more prominent in the embryo than in the endosperm, particularly with ageing of the fruit. The possible significance of these changes in the growth factors has been discussed in relation to the age of the seed and the development of the embryo inside it.     

Micromorphology of fruits and seeds of Iranian Geranium (Geraniaceae), and its systematic significance

The fruit and seed micromorphology of 22 species of Geranium, representing the eight sections of the genus represented in Iran (G. sectt. Dissecta, Geranium, and Tuberosa of subgen. Geranium; sectt. Batrachioidea, Divaricata, Lucida, Ruberta and Trilopha of subgen. Robertium), have been examined by scanning electron microscopy (SEM). Macro‐ and micromorphological characters, including fruit and seed shape, size, color, hair type and density, mericarp ornamentations, hilum position, seed coat pattern, epidermal cell shape, and anticlinal and periclinal cell walls, are presented. Two microsculpturing patterns are recognized on the mericarp surface: reticulate and pusticulate. The micromorphology of the seed coat showed four distinctive cell patterns. The seed epidermis is constructed either of polygonal, elongated polygonal, or square to rectangular cells. The polygonal type is the most common among the studied species, but the variation in testa cell characters, their size and shape, may provide further information and useful diagnostic characters at specific and infraspecific rank. The shape and color of the seeds are, however, of little systematic value. Fruit characters were found to be important for separating taxa at infrageneric rank and our results show that the species can be separated into subgenera and sections based on fruit morphology.