A new species of Memecylon (Melastomataceae) from India

Memecylon sivadasanii , a new species of Melastomataceae from India is described and illustrated. The new species is allied to M. angustifolium and M. rivulare.     

EMBRYOGENESIS AND SEEDLING DEVELOPMENT IN CASSIPOUREA ELLIPTICA (SW.) POIR. (RHIZOPHORACEAE)

Embryogenesis in Cassipourea elliptica (Sw.) Poir, begins with a first division of the zygote which may be oriented transversely, obliquely, or rarely longitudinally. The orientation of the second division is also variable. Though the differentiation of suspensor and embryo proper occurs early, some derivatives of the terminal cell sometimes contribute to the suspensor. Provascular tissue “differentiates” after the initiation of the cotyledons. The radicle apical meristem originates subterminally, 5–10 cell layers from the juncture of the embryo proper and the suspensor. After germination, during early seedling establishment, radicle apical organization is of an unspecialized, columellate type. Vascular differentiation occurs before germination, and there are two loci of initial xylem differentiation: one in the hypocotyl and another in the median trace of the cotyledons. After germination, additional xylem differentiates de novo (without lateral or longitudinal continuity with already-mature vessels) inside the arcs of phloem in the hypocotyl, a pattern reported in few angiosperms. The cotyledonary node is one-trace, unilacunar.     

Two new species in Memecylon (Melastomataceae) from India

Two new species in Memecylon, M. kollimalayana and M. bremeri , of Melastomataceae are described here with illustrations from the Kollihills of Salem District in Tamil Nadu, India.     

Foliar sclereids in Memecylon and Lijndenia (Melastomataceae) from Borneo, Java, Malaya and Sumatra

Foliar sclereids are investigated in 41 Memecylon species and in Lijndenia laurina Zoll. & Mor. (= Memecylon oligoneurum Bl.). The predominance of filiform sclereids in the Memecylon species is remarkable. Lijndenia laurina has ramiform sclereids.     

Memecylon trunciflorum sp. nov. (Melastomataceae–Olisbeoideae) from the Udzungwa Mountains,southern Tanzania

Described and illustrated is Memecylon trunciflorum R. D. Stone, an evidently localized endemic of the Udzungwa Mountains in southern Tanzania. The new species was previously confused with the vegetatively similar but distantly related M. erythranthum Gilg and M. semseii A. Fern. & R. Fern., from which it is distinguished by its anther connectives bearing a dorsal oil‐gland and by its ellipsoid to obovoid fruits (vs anther connective gland absent and fruits globose in M. erythranthum and M. semseii). The new species is placed in M. sect. Magnifoliata R. D. Stone together with M. magnifoliatum A. Fern. & R. Fern., from which it differs by its smaller leaves mostly 9.5–15.0 × 3.5–6.0 cm (vs 18–35 × 8–13 cm), transverse veins 8–18 pairs (vs 25–28 pairs), short‐pedunculate inflorescences with secondary axes well developed (vs peduncles and secondary axes absent), white flowers (vs bluish purple), and smaller fruits mostly 11.5–14.5 × 9–11 mm on longer fruiting pedicels 8.0–13.5 mm (vs fruits 17–20 × 12–14 mm on pedicels 5.0–7.5 mm). Despite its local endemism, Memecylon trunciflorum has been assessed as ‘Least Concern’ according to IUCN criteria, although this assessment is dependent on the continued safeguarding of the Udzungwa Mountains National Park.     

Evolution under domestication: contrasting functional morphology of seedlings in domesticated cassava and its closest wild relatives

Although cassava (Manihot esculenta ssp. esculenta) is asexually propagated, farmers incorporate plants from seedlings into planting stocks. These products of sex are exposed to selection, which in agricultural environments should favour rapid growth. To examine whether seedling morphology has evolved under domestication, we compared domesticated cassava, its wild progenitor (M. esculenta ssp. flabellifolia) and their sister species (M. pruinosa) under controlled conditions. Field observations complemented laboratory study. In both wild taxa, the hypocotyl did not elongate (hypogeal germination) and cotyledons remained enclosed in the testa. In domesticated cassava, the hypocotyl elongated (epigeal germination), and cotyledons emerged and became foliaceous. The difference in hypocotyl elongation was fixed, whereas cotyledon morphology varied with environmental conditions in M. pruinosa. Comparative analysis suggests that epigeal germination is primitive in Manihot, that the lineage including wild ancestors of cassava evolved hypogeal germination--which confers greater tolerance to risks in their savanna environment--and that with domestication, there was a reversion to epigeal germination and photosynthetic cotyledons, traits conferring high initial growth rates in agricultural habitats.     

The seedling characters of Chinese Calycanthaceae with a new species of Chimonanthus Lindl.

This paper deals with morphological characters in seedlings and adult plants of 5 species of Chinese Calycanthaceae. The germination of seeds, morphology of cotyledons, hypocotyl and primary leaves of these species are enumerated, for example, the Chimonanthus campanulatus, sp. nov. is characterized by half-hypogaeous and tetragonal cotyledons, whereas other species epigaeous; the cotyledons of Calycanthus chinensis is obtriangular, Chimonanthus praecox, Ch. salicifolius and Ch. nitens are reniform. On the morphological characters of these adult plants and geographical distribution of 4 species of Chimonanthus are keyed. In addition a new species, Chimonanthus campanulatus, is described and it represents a more primitive type of the genus.     

The Influence of Cotyledons in Axillary and Adventitious Shoot Production from Cotyledonary Nodes of Cucumis sativus L. (Cucumber)

Cucumber explants including at least part of the cotyledon,a short section of hypocotyl, and the apical bud, are capableof producing multiple axillary buds from the seedling apex andadventitious shoots from the hypocotyl base in a medium whichcontains 2·0 mg dm^–3 of kinetin. Removal of theapical bud triples the number of shoots produced from the apexof explants with two intact cotyledons but does not affect shootproduction from explants with some or all of their cotyledonsremoved. The area of intact cotyledon also influences morphogenesis,as explants with both cotyledons removed, failed to produceadventitious shoots from the hypocotyl base. Culture in continuousdarkness entirely prevents shoot development from the explantbase, but has little influence on shoot production from theapex. The influence of endogenous growth regulators and apicaldominance on the morphogenesis of shoots in cucumber seedlingsare discussed. Key words: Cucumber, cotyledons, apical dominance, morphogenesis, adventitious shoots, Cucumis sativus     

A conifer seedling with two herbicolous fungi from the Baltic amber forest

A Baltic amber inclusion of a fossil spruce seedling of which the lower part of the hypocotyl and the primary root are not preserved is provisionally described as Picea baltica ad int. The remnant of the hypocotyl and the basal parts of the cotyledons are infested by a conidial fungus. Its conidiophores correspond to those of the genus Gonatobotryum Corda. However, the fungus is not assignable to any extant species and is therefore described as a new species, Gonatobotryum piceae . A further infestation, most probably by a stroma-forming anamorph, is visible on the cotyledons of the seedling. Its mode of infestation is similar to that of Sirococcus strobilinus Preuss which occurs in extant spruce seedlings.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 155 , 449–456.     

VASCULAR INFECTION OF COTTON BY XANTHOMONAS MALVACEARUM (E. F. SMITH) DOWSON

Cotton seedlings raised under glass from seed pre-soaked in a water suspension of Xanthomonas malvacearum , and watered by sub-irrigation only, developed atypical dull green flaccid areas extending from the periphery of the cotyledons. Later symptoms that variably developed were: vascular discoloration, not necessarily continuous, in the petioles of affected cotyledons, in the hypocotyl, and in parts of the plant above the cotyledonary node; premature withering of cotyledons; dull green flaccid areas in true leaves, not necessarily the lowest, later turning brown and drying, with usually a chlorotic margin; parenchymatous attack in stems, petioles and leaves. Evidence is adduced, from the progression of symptoms and from associations between them, and from isolations of the pathogen from various parts of the plant at different stages, that the course of this type of infection is primarily vascular, progressing from the edges of cotyledons into the hypocotyl and thence upwards in vascular tissues. Thence the infection may break out at any time into parenchymatous tissues, leading to the more characteristic forms of the disease, of greater or less severity according to the susceptibility of the parenchyma at the time of its invasion. Similar symptoms have been observed in field plantings, and it is suggested that vascular infection is of greater and wider significance in the epidemiology of bacterial blight than has hitherto been commonly accepted.     

Organ- and Tissue-specific Biosynthesis of Flavonoids in Seedlings of Oenothera odorata (Onagraceae)

In developing Oenothera odorata seedlings, phytochrome-mediated accumulation of various flavonoids (mainly glycosides of cyanidin and quercetin) is detectable, subsequent to a transient induction of the key enzymes of the general phenylpropanoid metabolism, L-phenylalanine ammonia lyase (PAL) and of flavonoid biosynthesis, chalcone synthase (CHS). Organ- and tissue-specific distribution of these enzymes and of the flavonoid end products was investigated in seedlings, irradiated with continuous far-red light. Anthocyanins and quercetin glycosides are mainly localized in both the upper and lower epidermis of the cotyledons and to a lesser extent also in the epidermal cell layer of the hypocotyl. An obvious organ-specific distribution was observed for the anthocyanins: cyanidin-3,5-O-diglucoside accumulates in the epidermal cells of the cotyledons, whereas cyanidin-3-O-glucoside is restricted to the epidermis of the hypocotyl. By contrast the pattern of quercetin glycosides is the same in the cotyledons and in the hypocotyl. The methylated flavonol aglycone 3-0-methylquercetin was found to be localized in the seed coat. According to this organ- and tissue-specific pattern of flavonoids, immunochemical and immunohistochemical detection of PAL and CHS revealed a predominant localization of theenzymes in the epidermal layers of the cotyledons and the hypocotyl but also in the cells surrounding the vascular bundles. The role of compartmentation in regulation of flavonoid biosynthesis and putative functions of flavonoid compounds are discussed.     

宁夏枸杞的胚胎发生和胚乳发育

宁夏枸杞的胚胎发生属茄型,由顶细胞参与胚体的形成,基细胞仅形成六细胞胚柄。胚乳发育为细胞型,但也观察到少数核型胚乳的现象。初步探讨了核型胚乳与细胞型胚乳的关系。     

Factors influencing plant regeneration from seedling explants of Hairy nightshade (<Emphasis Type="Italic">Solanum sarrachoides</Emphasis>)

Hairy nightshade (Solanum sarrachoides) has the potential to be a model system for the study of plant-pathogen interactions, however, the availability of tissue culture and transformation methods would strengthen its utility. For the development of tissue culture methods, we investigated, explant type (cotyledons, hypocotyls, roots), hypocotyl explant origin, cotyledon orientation (abaxial vs. adaxial) in direct contact with the medium, gelling agents (agar and agargel) and cytokinins (zeatin and 6-benzyladenine) at different concentrations. Cotyledon explants resulted in the greatest biomass as compared to root and hypocotyl. As for hypocotyl explant origin, explants proximal to the cotyledons had a significant effect on plant regeneration. However, cotyledon orientation and gelling agent had no effect on plant regeneration. Medium supplemented with either zeatin or 6-benzyladenine at 1 mg L⁻¹ resulted in significant shoot regeneration. Shoots rooted readily when cultured on a non-hormone based rooting medium.     

Effect of benzyladenine on development of derooted watermelon seedlings

We have examined the effects of benzyladenine (BA) on derooted watermelon ( Citrullus vulgaris Schrad., cv. Fairfax) seedlings with special attention to the cotyledons. The growth regulator was supplied either as a droplet of solution between the cotyledons (application from above) or through the hypocotyl stump (application from below). Application of BA from above stimulates several developmental parameters of cotyledons [growth, lipid breakdown, chlorophyll and carotenoid accumulation, hydroxypyruvate reductase (EC 1.1.1.81.) activity]. The stimulation is much smaller with application from below. Also the distribution of labelled BA changes according to the method of application. The bulk of the label remains in the cotyledons when BA is supplied from above and in the hypocotyl when it is supplied from below. The absolute amount of radioactivity found in the cotyledons after 24 h of treatment is approximately the same in both cases. This seems to indicate that the different effects of the two treatments depend on concentration ratios of BA (or metabolic derivates) between hypocotyl and cotyledons rather than on absolute growth regulator levels.     

Somatic embryogenesis in wild cherry (Prunus avium)

Indirect somatic embryogenesis was obtained inPrunus avium L. from either somatic or zygotic embryos. An embryogenic line was established by reinduction of embryogenic calluses from somatic embryos. The line was maintained for more than 3 years through 6 generations of embryogenic cultures. In the last 2 generations, more than 50% of the explants were embryogenic. Embryos at different stages of development were produced. Among cotyledonary-stage embryos, 50% had two cotyledons and a distinct hypocotyl, 43% had one or more than 2 cotyledons and 7% had fused cotyledons. Most of the embryos were translucent and conversion into plantlets was very rare. Secondary embryos could be observed to occur with low frequency from cultured somatic embryos and from embryos emerging from calluses. Indirect somatic embryogenesis was also induced from immature zygotic embryos. From one donor tree, 51% of the explants were embryogenic when cultured on a medium containing 0.9 μM kinetin, 0.9 μM BA and 0.5 μM NAA. This revised version was published online in June 2006 with corrections to the Cover Date.     

Inter-organ Synergism and the Control of Chlorophyll Accumulation in Sunflower (Helianthus annuus) Cotyledons

Prior to illumination, the embryonic axis of sunflower seedlingsmakes a contribution to the cotyledons which enables them togreen more rapidly when subsequently irradiated with white light.The contributions made to this stimulation by the hypocotylhook, hypocotyl, and roots have been investigated. Greeningin sunflower cotyledons reaches an optimum rate when they are6 d old. The developing embryonic axis not only promotes theattainment of this optimum rate but also aids in the maintenanceof this optimum rate as the cotyledons continue to age. Thisstimulatory effect appears to arise primarily from the rootsand can be duplicated by the exogenous application of benzyladenine. In contrast to previous reports we find that the hypocotyl hookplays no role in the control of greening when present duringillumination.     

Uptake, transport and metabolism of 14C-2,4-dichlorophenoxyacetic acid (14C-2,4-D) in cucumber (Cucumis sativus L.) explants

The uptake, distribution and metabolism of 2,4-D using 14C-labelled 2,4-dichlorophenoxyacetic acid (14C-2,4-D) was studied in isolated hypocotyl and cotyledon explants of cucumber (Cucumis sativus L.) in vitro. Cotyledons had a higher uptake capacity than hypocotyls; the uptake in cotyledons increased linearly up to 20 h, while in hypocotyls only up to 8 h. The distribution of 14C-activity in both organs was basipetal, but more pronounced in cotyledons. The 2,4-D taken up by cotyledons was metabolized very rapidly: only 7% of 14C-activity was associated with free 2,4-D after 20 h exposure. Hypocotyls metabolized 2,4-D more slowly: after 20 h 50% of the 14C-activity was still associated with free 2,4-D. After short incubation periods (2–5 h) 2,4-D-aspartate was a predominant metabolite, after longer incubation (8–20 h) 2,4-D-glucosyl ester prevailed. Roots or callus were formed on the base of cotyledons depending on the length of exposure to 2,4-D.     

Comparative developmental anatomy of seedlings in nine species of podostemaceae (subfamily Podostemoideae)

The developmental anatomy is described for seedlings of nine Asian and Australian species of Podostemaceae, subfamily Podostemoideae. The hypocotyl is rudimentary (except in Zeylanidium olivaceum) and does not form a primary root in any of the species examined. An adventitious root forms endogenously in the hypocotyl of six species with ribbon-like or flattened subcylindrical roots, and in Z olivaceum with foliose roots. In contrast, it forms exogenously in Hydrobryum griffithii and Synstylis micranthera with foliose roots. The juvenile root becomes flattened and dorsiventral, branches exogenously (in Polypleurum stylosum, P. wallichii and Z. lichenoides) and produces shoots endogenously (in P. stylosum, P. wallichii, S. micranthera and Z. lichenoides). The root meristem is simple, composed of surface and uniform inner cells, and is devoid of root cap initials in all species. The reduced meristem morphology of seedling roots may be primitive in the Asian-Australian Podostemoideae. A root cap or protective tissue did not form during the culture period, even in the seven species with capped adult roots, probably due to its delayed development. It was absent throughout ontogeny in the other two species. No obvious shoot apical meristem forms between the cotyledons. One to several leaves occupy the shoot apical area in species with endogenous adventitious roots, while no leaves are formed in species with exogenous roots. These differences suggest recurrent origins of foliose roots in the Asian clade. Similarities between the unique seedling morphology and mutant Arabidopsis phenotypes are discussed.     

台闽苣苔（苦苣苔科）幼苗的发育式样及其意义

为解决台闽苣苔族 (Titanotricheae)这一单种族的科级系统位置 ,通过扫描电镜观察了台闽苣苔 (Titan otrichumoldhamii (Hemsl.)Solereder)植物的种子发芽和幼苗发育过程。随着下胚轴的向下伸长 ,两个子叶开始不明显的异率生长 ,其中一片子叶略大于另一片子叶。但两片子叶均正常发育并位于同一高度。当真叶发出后 ,两片子叶几乎等大 ,并且两个子叶柄等长。在幼苗生长期间 ,随着子叶的生长 ,胚芽也正常萌发出茎的顶芽。顶芽持续进行顶端生长产生交互对生的真叶。这一幼苗生长式样和苦苣苔亚科其他类群的仅一片子叶发育与胚芽被抑制的幼苗生长式样有明显区别。考虑到台闽苣苔植物在总状花序的上部大量簇生无性珠芽 ,并落地迅速生长出新的植株这一在苦苣苔科中独特的无性繁殖方式及相关性状 ,台闽苣苔族可能较早地从苦苣苔亚科中分化出来 ,并在繁殖体的功能进化方面和其他类群发生歧化进而获得独特的无性繁殖方式。台闽苣苔族在系统发育上应该被认为是其他苦苣苔亚科类群的姊妹群 ,应当提升为亚科等级。