MORPHOLOGY AND VASCULATURE OF THE LEAF OF POTATO (SOLANUM TUBEROSUM)

The leaf and stem of the potato plant (Solanum tuberosum L. cv. Russet Burbank) were studied by light microscopy to determine their morphology and vasculature; scanning electron microscopy provided supplemental information on the leaf's morphology. The morphology of the basal leaves of the potato shoot is quite variable, ranging from simple to pinnately compound. The upper leaves of the shoot are more uniform, being odd pinnate with three major pairs of lateral leaflets and a number of folioles. The primary vascular system of the stem is comprised of six bundles, three large and three small ones. The three large bundles form a highly interconnected system through a repeated series of branchings and arch-producing mergers. Two of the three large bundles give rise to short, lateral leaf traces at each node. Each of the small bundles in the stem is actually a median leaf trace which extends three internodes before diverging into a leaf. The three leaf traces enter the petiole through a single gap; thus the nodel anatomy is three-trace unilacunar. Upon entering the petiole, each of the laterals splits into an upper and a lower lateral. Whereas the upper laterals diverge entirely into the first pair of leaflets, the lower laterals feed all of the lateral leaflets through a series of bifurcations. Prior to their entering the terminal leaflet, the lower laterals converge on the median bundle to form a single vascular crescent which progresses acropetally into the terminal leaflet as the midvein, or primary vein. In the midrib, portions of the midvein diverge outward and continue as secondaries to the margin on either side of the lamina. Near the tip of the terminal leaflet, the midvein consists of a single vascular bundle which is a continuation of the median bundle. Six to seven orders of veins occur in the terminal leaflet.     

FLORAL DEVELOPMENT AND VASCULATURE IN HYDROCLEIS NYMPHOIDES (BUTOMACEAE)

The flower of Hydrocleis nymphoides consists of three sepals which arise in spiral succession, three simultaneously arising petals, numerous stamens and staminodia which arise in centrifugal order, and six carpels. A residual apex remains at maturity. The first-formed members of the androecium are stamens and the later-formed members are staminodia which develop below the stamens and which become outwardly displaced during expansion of the receptacle. The androecium is supplied by branching vascular trunk bundles. The carpels are completely open but the ventral margins are slightly conduplicately appressed basally. A single dorsal bundle provides the stigmatic area with vascular tissue, and a network of small placental bundles supplies the numerous laminar ovules. There are no clearly defined ventral bundles. It is suggested that Hydrocleis nymphoides is neither the most primitive nor the most advanced member of the family. A pattern of phylogenetic reduction in the androecium and receptacle is suggested for the entire family.     

MORPHOLOGY AND DEVELOPMENT OF THE FLOWERS OF BOOTTIA CORDATA,OTTELIA ALISMOIDES,AND THEIR SYNTHETIC HYBRID (HYDROCHARITACEAE)

The inferior ovary of Boottia cordata, Ottelia alismoides, and their hybrid is appendicular in nature, the carpels are congenitally only slightly connate, and they are unsealed. All floral organs except the sepals originate from common primordia in the female and bisexual flowers. A flat residual floral apex is pressnt. There is a vestigial superior ovary of three ontogenetically fused carpels in the male flower of Boottia cordata. The hybrid is intermediate in many characteristics and has partially fertile stamens and staminodia. The sequence of development in all flowers is acropetal. These plants appear to be related to the Butomaceae and they show evolutionary tendencies parallel to those in the Nymphaeaceae.     

ORGAN INITIATION AND THE DEVELOPMENT OF UNISEXUAL FLOWERS IN THE TASSEL AND EAR OF ZEA MAYS

The development of the unisexual male and female flowers of Zea mays from bisexual initials in both tassels and ears has been reinvestigated with SEM and TEM. The early stages of spikelet branch primordia, spikelet initiation, and early flower development are similar in both flowers, though differences in rates of growth of glumes, lemmas, and palea were detected. In both tassel and ear flowers, a pair of stamens arises opposite the lemmas and a third stamen initiates later at right angles to the first pair but from a point on the meristem below its insertion. Gynoecia develop on both tassel and ear flowers first as a ridge which overgrows the apical meristem giving rise to the stylar canal and the elongate silk. Male flowers arise in the tassel through selective vacuolation and abortion of the cells of the early gynoecium. The single female flower in each ear spikelet arises through the vacuolation and abortion of stamens in the upper flower and the repression of growth of and the eventual regression of the lower flower in each spikelet. The significance of these selective organ abortions for practical applications is discussed.     

ORGAN INITIATION AND DEVELOPMENT OF INFLORESCENCES AND FLOWERS OF ACACIA BAILEYANA

Inflorescence and floral ontogeny are described in the mimosoid Acacia baileyana F. Muell., using scanning electron microscopy and light microscopy. The panicle includes first-order and second-order inflorescences. The first-order inflorescence meristem produces first-order bracts in acropetal order; these bracts each subtend a second-order inflorescence meristem, commonly called a head. Each second-order inflorescence meristem initiates an acropetally sequential series of second-order bracts. After all bracts are formed, their subtended floral meristems are initiated synchronously. The sepals and petals of the radially symmetrical flowers are arranged in alternating pentamerous whorls. There are 30–40 stamens and a unicarpellate gynoecium. In most flowers, the sepals are initiated helically, with the first-formed sepal varying in position. Petal primordia are initiated simultaneously, alternate to the sepals. Three to five individual stamen primordia are initiated in each of five altemipetalous sectorial clusters. Additional stamen primordia are initiated between adjacent clusters, followed by other stamens initiated basipetally as well as centripetally. The apical configuration shifts from a tunica-corpus cellular arrangement before organogenesis to a mantle-core arrangement at sepal initiation. All floral organs are initiated by periclinal divisions of the subsurface mantle cells. The receptacle expands radially by numerous anticlinal divisions in the mantle at the summit, concurrently with proliferation of stamen primordia. The carpel primordium develops in terminal position by conversion of the floral apex.     

ULTRASTRUCTURAL DEVELOPMENT OF THE BEETLE FOOD TISSUE OF CALYCANTHUS FLOWERS

The flower of Calycanthus traps a wide variety of beetles which, while imprisoned, effect pollination. During their occupancy the insects eat a protein-rich tissue developed at the tips of the inner tepals, stamens, and staminodia. Cells of this food tissue differentiate a large number of cytoplasmic protein tubules by using a protein vacuole as an assembly site. The cells comprising the food tissue represent a very specialized plant cell type and one which facilitates this particular plant/insect relationship.     

MORPHOLOGY AND DICHOTOMOUS VASCULATURE OF THE LEAF OF KINGDONIA UNIFLORA

Foster , Adriance S. (U. California, Berkeley), and Howard J. Arnott . Morphology and dichotomous vasculature of the leaf of Kingdonia uniflora. Amer. Jour. Bot. 47 (8): 684–698. Illus. 1960.—An intensive study of the nodal anatomy, petiolar vasculature and open dichotomous venation of the leaf of Kingdonia has revealed a type of foliar vascular system of unusual morphological and phylogenetic interest. The vascular supply at the nodal level consists of 4 collateral traces which diverge from a single gap into the sheathing leaf base. This type of nodal anatomy is perhaps primitive, and comparisons are made with the unilacunar nodes and the 2- and 4-parted leaf trace systems characteristic of many angiospermous cotyledons and the foliage leaves of certain woody ranalian genera. The petiole of Kingdonia is vascularized by 2 pairs of bundles which represent the upward continuation of the 4 leaf traces. A transition from an even (4) to an odd (3) number of strands occurs near the point of attachment of the 5, lobed, cuneiform lamina segments to the petiole. Each of the 2 abaxial bundles dichotomizes and the central derivative branches fuse to form a double bundle which enters the base of the median lamina segment. The 2 adaxial petiolar bundles diverge right and left into the bases of the paired lateral segments of the lamina. An analogous type of transition from an even to an odd number of veins occurs in many angiospermous cotyledons which develop a definable mid-vein. But, in Kingdonia, the bundles which enter the bases of the lamina segments give rise to systems of dichotomizing veinlets devoid of “mid-veins.” Although the majority of the terminal veinlets enter the marginal teeth of the lamina segments, “blind” endings, unrelated to the dentations, occur in all the leaves studied. Typically, all of the vein endings in a given lobule of a lamina segment are derived from the same dichotomous vein system. However, in some leaves, a veinlet dichotomizes directly below a sinus and the branches diverge into the marginal regions of 2 separate lobules. The phylogenetic significance of the occurrence of open dichotomous venation in such an herbaceous angiosperm as Kingdonia is briefly discussed. From a purely morphological viewpoint, the Kingdonia type of venation invites direct comparison with the venation of Sphenophyllum, certain ferns or Ginkgo rather than with any of the known reticulate venation patterns of modern angiosperms. Although the foliar venation of Kingdonia may represent the result of evolutionary reversion, the very rare anastomoses which occur seem primitive in type rather than “vestiges” of a former system of closed venation.     

中国慈姑属系统发育的研究

本文研究了中国慈姑属植物间的系统发育关系。选取了12个与该属系统发育有较重要关系的特征,将8个已知分类群与外类群刺果泽泻属进行了比较。应用数量分支分析的Farris-Wagner方法,建立了中国慈姑属系统发育分支图。讨论了各分类群间的系统发育关系、该属起源和数量分支分析方法等问题。     

EVOLUTION OF COTYLEDONARY AND NODAL VASCULATURE IN THE JUGLANDACEAE

Cotyledonary nodal patterns of the Juglandaceae range from 1-gap, 2-trace to multi-gap, multi-trace. The development of increased nodal complexity is associated with at least two independent evolutionary shifts from epigeal to hypogeal germination. The taxa with epigeal germination such as Engelhardia sect. Engelhardia, Engelhardia sect. Psilocarpeae, Platycarya, and Pterocarya all have 1-gap, 2-trace nodes. The change to hypogeal germination in Engelhardia sect. Oreomunnea and Alfaroa is correlated with the development of 1-gap, 3-trace cotyledonary nodes. The second line has led to large, heavy-fruited members with hypogeal germination and complex cotyledonary nodes ranging from 2–6 gaps. The diversity of nodal patterns is the result of variation on a common theme; five basic vascular strands in the cotyledon, undergoing variations in dichotomy, fusion, and separation, are associated with one to many gaps. Presumably the complex development of the cotyledonary node is a response to increased functional demands of hypogeous cotyledons.     

CHROMOSOMAL REARRANGEMENTS AND THE GENETICS OF REPRODUCTIVE BARRIERS IN MIMULUS (MONKEY FLOWERS)

Chromosomal rearrangements may directly cause hybrid sterility and can facilitate speciation by preserving local adaptation in the face of gene flow. We used comparative linkage mapping with shared gene‐based markers to identify potential chromosomal rearrangements between the sister monkeyflowers Mimulus lewisii and Mimulus cardinalis, which are textbook examples of ecological speciation. We then remapped quantitative trait loci (QTLs) for floral traits and flowering time (premating isolation) and hybrid sterility (postzygotic isolation). We identified three major regions of recombination suppression in the M. lewisii × M. cardinalis hybrid map compared to a relatively collinear Mimulus parishii × M. lewisii map, consistent with a reciprocal translocation and two inversions specific to M. cardinalis. These inferences were supported by targeted intraspecific mapping, which also implied a M. lewisii‐specific reciprocal translocation causing chromosomal pseudo‐linkage in both hybrid mapping populations. Floral QTLs mapped in this study, along with previously mapped adaptive QTLs, were clustered in putatively rearranged regions. All QTLs for male sterility, including two underdominant loci, mapped to regions of recombination suppression. We argue that chromosomal rearrangements may have played an important role in generating and consolidating barriers to gene flow as natural selection drove the dramatic ecological and morphological divergence of these species.     

黄瓜雄花形成过程中心皮的发育

黄瓜(Cucumis sativus L.)为重要的经济作物,雌雄同株异花,是研究植物性别分化的经典材料。人们对黄瓜性别分化进行了广泛的研究。Astmon和Galun、任吉君和王艳对黄瓜性别分化的形态特征和器官发生进行了初步研究,表明黄瓜单性花分化和发育过程中经历了无性期、两性期和单性期,最终只有一种性别的性器官原基发育成有功能的性器官,从而形成单性花,而对单性花中未形成有功能器官的相反性别原基的研究报道甚少。我们对雄花发育过程进行了连续的形态学分析,并对不同时期雄花中的心皮进行了细胞计数和同工酶电泳分析,以期从性器官发育的角度探讨黄瓜性别表现的机理。