DEVELOPMENT OF THE SEED OF SOLANUM PHUREJA

Dnyansagab , Vishnu R., and Delmer C. Cooper . (U. Wisconsin, Madison.) Development of the seed of Solanum phureja. Amer. Jour. Bot. 47(3) : 176—186. Illus. 1960.—Ontogeny of the seed of Solanum phureja Juz. et Buk. is described. The megagametophyte, during the course of its development, ruptures the nucellus and at maturity lies in direct contact with the inner layer (endothelium) of the single massive integument. The mature megagametophyte, a 7-celled structure, consists of a 3-celled egg apparatus, an endosperm mother cell with fused polar nuclei and 3 persistent antipodals. Both 2- and 3-celled mature pollen grains are formed within anthers of the same flower; hence this character cannot be considered of any taxonomic value. Double fertilization occurs between 24 and 72 hr. after pollination. A cellular endosperm is formed, the peripheral layer acting as an absorbing tissue during the early ontogeny of the seed. Later this layer becomes organized as an aleurone layer and thereafter the source of nutrients is via the basal portion of the endosperm immediately adjacent to the apical end of the vascular tissue of the developing seed. Embryo development follows the Nicotiana variation of the Solanad type. The mature testa is composed of an outer layer of thick-walled epidermal cells, an inner layer of thin-walled cells and an intervening mass of disorganized tissue. In those instances where the ovule or young seed aborts, the endothelial cells of the integument become hyperactive and proliferate to such an extent that the space formerly occupied by the gametophyte or the developing endosperm and embryo becomes completely filled with endothelial tissue.     

THE DEVELOPMENT OF THE SEED OF ABUTILON THEOPHRASTI. II. SEED COAT

Winter , Dorothy M. (Iowa State U., Ames.) The development of the seed of Abutilon theophrasti. II. Seat coat. Amer. Jour. Bot. 47(3) : 157—162. Illus. 1960.–The integuments of Abutilon theophrasti Medic. undergo a rapid increase in size, predominantly by anticlinal cell divisions during the first 3 days after fertilization. Within 7 days, the outer epidermis of the inner integument becomes thick walled. At maturity this compact, lignified, and cutinized palisade layer accounts for more than half the thickness of the seed coat. During early growth, the palisade cells form a continuous layer in the micropylar region. In the chalazal region the palisade layer is discontinuous in a slit-shaped region, 60 × 740 microns. The shape of this discontinuity constitutes a major difference between dormant-seeded Abutilon and non-dormant Gossypium seeds. Exterior to the palisade layer is the outer integument which consists of a small-celled layer and a large-celled layer sparsely covered with unicellular, lignified hairs. Interior to the palisade is the thick mesophyll of the inner integument which is largely digested during seed growth and leaves only 2 pigmented cell layers in most regions at maturity. The inner epidermis is small-celled, pigmented and cutinized and adheres tightly to the endosperm. Seed coat impermeability increases with seed maturity. Even immature seeds will germinate, if scarified, indicating a lack of embryo dormancy.     

GIBBERELLIN-LIKE SUBSTANCES OCCURRING IN THE SEED OF PHARBITIS NIL CHOIS. AND THEIR CHANGE IN CONTENTS DURING THE SEED DEVELOPMENT

The amount of gibberellin-like substances in the seed of Pharbitisnil increased in parallel with the growth of the seed, and attained20 days after anthesis to a maximum of 0.115 µg gibberellinA₃ eqivalent per seed, when the seed reached its maximum freshweight or four-fifths of its final dry weight. At this maximumlevel, 0.03 µg and 0.1 µg gibberellin A₃ equivalentswere localized in the embryo and in the "endosperm", respectively.Three gibberellin-like substances (Factors I, II and III) wereseparated upon paper chromatography. In view of the changesin amount of the factors with respect to the seed maturation,these factors, especially Factor II, in the "endosperm" andembryo were assumed to participate in the initial or the mainpart of growth of the embryo. Dwarf rice seedling and maizedwarfs 1, 3 and 5 responded to the three factors nearly in thesame way. Pharbitis dwarf, however, responded only to FactorI, but not to Factors II and III. (Received February 21, 1963; )     

ON THE DEVELOPMENT OF MACROSCLEREIDS IN SEED COATS OF PISUM SATIVUM L.

Macrosclereid differentiation was investigated by light and electron microscopy in pea testae during the transformation of protodermal precursors to the mature sclereids. The protodermal cells divide anticlinally and elongate into the macrosclereid layer during seed coat development. Young sclereids have elongate nuclei, plastids become somewhat granal during cellular maturation, vacuolation appears to be an autolytic process, and the cells have dense arrays of endoplasmic reticulum and ribosomes. Considerable dictyosome activity and microtubule development is observed as the secondary wall is produced. Many coated vesicles are associated with and fuse with the plasmalemma. During development, the outer tangential wall area of the macrosclereids acquires a definite cuticle and subcuticular layer. Also, at this time the sclereid walls under the subcuticular layer display semicircular microfibril orientation. The sclereid walls adjacent to the hypodermis become multilayered. As the macrosclereids near maturity, the “light line” becomes discernable in the light microscope at the junction of the cellulosic tips of the macrosclereids and the subcuticular layer. This “light line” is prominent using interference optics and is an osmiophilic layer in the electron microscope. This layer may represent the suberin “caps” reported by earlier workers.     

PLEIOTROPIC EFFECTS ON SEED DEVELOPMENT OF THE INDETERMINATE GAMETOPHYTE GENE IN MAIZE

Not more than half the seeds borne by maize plants of the W23 inbred strain, homozygous for a mutant gene termed “indeterminate gametophyte” (ig), develop normally. The remainder exhibit polyembryony (6 %), heterofertilization (7 %), elevated ploidy level of the endosperm (45 %), or other less frequent anomalies. The ig effects were identified and characterized by chromosome counts and genetic tests. Twins were regularly found to be diploid and concordant for heterozygous marker genes introduced maternally. When the marker genes were introduced paternally, twins frequently were non-concordant, or the embryo and endosperm phenotypes did not correspond. The proportion of the various types and the absence of conjoined embryos indicated that, although identical in their maternal inheritance, the twins were regularly dizygotic. Those twins identical in paternal inheritance probably originate from the fertilization of two genetically identical eggs by the two sperm of one male gametophyte. When ig ig compared to normal diploid plants were pollinated by tetraploids, the proportion of plump seed formed was markedly increased. Evidently this result is the consequence of elevation of the endosperm ploidy level by the ig gene. The ig gene thus appears to interfere with differentiation of the components of the female gametophyte so that the number of eggs and polar nuclei, instead of being one and two, is indeterminate.     

MICROGAMETOPHYTE DEVELOPMENT IN THE PALEOZOIC SEED FERN FAMILY CALLISTOPHYTACEAE

Well-preserved stages of microgametophyte development are described from pollen produced by the Paleozoic seed fern family Callistophytaceae. Microgametophyte development in both the Middle Pennsylvanian pollen organ Idanothekion and Upper Pennsylvanian Callandrium involved the initial production of an axial row of at least three small prothallial cells proximally and a large embryonal cell distally. The arrangement and form of these cells is like that present in some extant genera of the Pinaceae. The prothallial cells were relatively large in comparison with extant gymnosperms, occupying the entire region of the cap-pus, and were apparently all primary. Evidence is presented that in Callandrium further development involved an anticlinal division of the large distal cell (antheridial initial) into a small generative cell contained within a larger tube cell. Previously described microgametophytes of the late Paleozoic order Cordaitales are reinterpreted and are shown to consist of an embryonal cell and three to four discoidal prothallial cells in an axial row like that of the Callistophytaceae. Microgametophytes thus far described from the Paleozoic are remarkably modern in appearance and provide no evidence to support the generally held view that the seed plant microgametophyte is an extremely reduced sexual phase that has arisen through the loss of almost all of the vegetative cells and the sterile outer cells of the antheridium. Evidence to support or refute this view will depend upon the discovery of microgametophytes from older groups of seed plants than those for which they are now known.     

槐种子发育中胚乳细胞半乳甘露聚糖积累的研究

槐 ( Sophora japonica L.)开花约 60 d至种子成熟 ,为胚乳半乳甘露聚糖积累期。用组织化学方法 ,对储藏于胚乳细胞壁上的半乳甘露聚糖的形成积累进行了观察 ,结果表明 ,半乳甘露聚糖最先在邻近胚的胚乳细胞的粗面内质网的囊泡腔内形成 ,并通过细胞质膜分泌至细胞壁周围。此后 ,半乳甘露聚糖的积累逐渐向种皮方向扩展 ,及至种子成熟时 ,除糊粉层外 ,所有胚乳细胞几乎全由多糖所填充。此外 ,对半乳甘露聚糖发生部位及其积累过程的消长变化进行了讨论     

STUDIES OF SEED FERN POLLEN: DEVELOPMENT OF THE EXINE IN MONOLETES (MEDULLOSALES)

Monoletes pollen extracted from the seed fern synangium Dolerotheca sclerotica Baxter illustrate four stages in the development of the sporoderm. In the first stage the grains are up to 100 μm long and possess an apparent homogeneous exine in which there is little differentiation between the nexine and sexine. Numerous nexine lamellae and the initiation of sexine expansion mark stage 2 in exine ontogeny. Further expansion of the sexine continues in the third stage until the ratio between the nexine and sexine is approximately 1:5. The final stage in maturation of the sporoderm shows an expanded alveolate sexine with some of the sporopollenin units broken and disorganized. It is at this stage of development that nexine lamellae are most prominent. The formation of sporoderm layers in the fossil grains is compared with pollen grain development in living cycads (Cycadophyta) and a model proposed to account for the apparent early formation of nexine lamellae in Monoletes. The evolution of exine components in early pollen types is discussed.     

THE DEVELOPMENT OF THE SEED OF ABUTILON THEOPHRASTI I. OVULE AND EMBRYO

Winter , Dorothy M. (Iowa State U., Ames.) The development of the seed of Abutilon theophrasti. I. Ovule and embryo. Amer. Jour. Bot. 47(1): 8–14. Illus. 1960.—Abutilon theophrasti Medic, is a widespread annual weed which produces an abundance of seed in capsules which mature within 20 days after pollination. Ovule differentiation may be observed at least 8 days before anthesis when a sporogenous cell becomes evident and 2 integuments are initiated. An 8-nucleate embryo sac is produced from the chalazal megaspore approximately 2 days before anthesis. The outer integument of the mature campylotropous ovule consists of 2 cell layers, the inner integument has 6 to 15 cell layers. The initially free-nucleate endosperm becomes cellular betwen 3 and 7 days after pollination. At maturity a thin layer of gelatinous endosperm encases the embryo. The Asterad-type proembryo of Abutilon has a stout suspensor and develops rapidly. Four days after pollination cotyledons are initiated; 4 days later a leaf primordium is evident. Fifteen days after pollination the embryo, which has essentially completed its growth, consists of a large hypocotyl with root promeristem and root cap at its basal end, and 2 flat, folded, leaflike cotyledons enclosing a small epicotyl at its upper end. The epicotyl consists of an embryonic leaf and a stem apex.     

EFFECT OF SEED SIZE ON HETEROBLASTIC DEVELOPMENT IN SEEDLINGS OF DESMODIUM PANICULATUM

Seedlings of Desmodium paniculatum derived from different seed sizes differed in heteroblastic development. The transition from juvenile to adult leaves took place at the fourth node in seedlings derived from larger seeds and at the fifth or sixth node in those derived from smaller ones. Cotyledon removal had no effect on this condition, but growth under reduced irradiance delayed the formation of adult leaves in seedlings from larger seeds. Simple and compound leaves had similar unit area photosynthetic rates and stomatal conductance values, but compound leaves had a 30% higher total area. The earlier production of adult leaves would thus give seedlings from larger seeds an advantage in terms of total carbon gain.     

无量山种子植物区系的特有现象

地处滇中南的无量山地区迄今计有种子植物２０７科,１０２６属,２５４０种,其中东亚特有科１０个,中国特有属２７个,无量山特有种子６７个,这一地区不仅植物种类丰富,而且特有现象较为显著,在对科级持有现象进行较细致的研究后,本文认国无量山具有较多的分类系统上隔离的东亚特有科反映了该地作为东亚古老植物区系的一部分,其地质历史与整个东亚是一致的,且与东亚植物区系的发端密切相关,属的特有现象表明,地处中国特有     

紫杉烷类化合物研究进展

综述了近年来紫杉烷类在植物化学和药物化学方面的研究进展。着重介绍新的紫杉烷类天然化学成分的分离及其半合成衍生物。