Morphological and Physiological Effects of Maleic Hydrazide on Tobacco

Tobacco plants (Nicotiana tabacum cv. Burley 21) were cultured in the greenhouse to the 18-leaf stage. The apical meristem was removed and subsequent axillary bud growth was removed by hand (controls) or axillary bud development was inhibited by application of maleic hydrazide. Compared with the controls, maleic hydrazide treated plants had a decreased stem diameter and stem weight, but an increased leaf weight and leaf weight/area. Plant height and leaf area were the same for both treatments. Maleic hydrazide inhibited translocation of ¹⁴C from a single leaf exposed to ¹⁴CO₂. Respiration was greater than in the controls three days after application of maleic hydrazide, but 9 and 14 days after application there were no differences in respiration between the two treatments. Maleic hydrazide did not affect photosynthetic activity.     

大麦胚和胚乳发育的相关性及贮藏营养物质的积累

大麦(Hordeum vulgare L.)开花后1d,见合子及退化助细胞,游离核胚乳尚未形成;开花后2～3d,胚为5及10个细胞,胚乳为游离核期;开花后4及5、6d,胚为梨形及长梨形,胚乳达细胞化期;开花后8d,胚为胚芽鞘期,糊粉层原始细胞产生;开花后10d,胚具1叶,糊粉层1～2层;开花后13d胚为2叶胚,亚糊粉层发生;开花后17d,3叶胚形成,糊粉层多为3层并停止分裂,菱柱形及不规则胚乳细胞分化;开花后21～29d,胚为4叶胚,胚乳进一步分化;开花后33d,胚为5叶成熟胚,胚乳亦成熟。淀粉、蛋白质在胚中积累始于开花后13d。在盾片中由基向顶发生,在胚芽鞘及叶原基中,首先在顶端出现。成熟盾片顶端的淀粉消失。开花后6d,胚乳开始积累淀粉;开花后10d,糊粉层及胚乳细胞积累蛋白质。开花17d后胚乳的蛋白质体多聚集,29d后蛋白质体显著减少。开花后17d,在盾片及糊粉层细胞中检测到油脂。果长或果长与稃片长之比和盾片长可作为不同发育期胚和胚乳的形态指标。     

Development of Embryo and Endosperm and Nutrient Accumulation in Vigna sesquipedalis (L.) Fruwirth

The structure of embryo sac, fertilization and development of embryo and endosperm in Vigina sesquipedalis (L.) Fruwirth were investigated. Pollization occures 7–10h before anthesis, and fertilization is completed 10 h after anthesis. After fertilization, wall ingrowths are formed at the micropylar and chalazal ends of the embryo sac. Embryo development conforms to the Onagrad type, and passes through 2 or more celled proembryo, long stick-shaped, globular, heart shaped, torpedo, young embryo, growing and enlarging embryo and mature embryo. Wall ingrowths are formed on the walls of basal cells and outer walls of the cells at basal region of suspenser. The suspensor remains as the seed reaches maturity. The starch grains accumulate in the cells of cotyledons by 9–16 days after anthesis, and proteins accumulate by 12–18 days after. The endosperm development follows the nuclear type. The endosperm ceils form at the micropylar end, and remain free nuclear phase at chalazal end. The outer cells are transfer cells. Those cells at the micropylar end form folded cells with wall ingrowths. At heartembryo stage, the endosperm begins to degenerate and disintegrates before the embryo matures.     

The Effect of Applied Growth Substances on Development of the Strawberry Fruit: I. INDUCTION OF PARTHENOCARPY

A series of experiments is described in which various growthregulators were applied in lanolin emulsions to the flowersof two pistillate varieties of strawberry, in an attempt topromote parthenocarpic development of their receptacles. Parthenocarpic development was obtained in a large majorityof the treated flowers over a range of concentrations, varyingfrom 500 p.p.m. to up to 6,000 p.p.m., after treatment withthe following growth regulators; 4-(indole-3-) butyric acid,2-naphthoxyacetic acid, and 1-naphthaleneacetic acid. Gibberellic acid promoted growth of the ‘neck’ regionin Freya and increased the response of this variety to 4-(indole-3-)butyric acid. It also reduced the period of development of thefruit from anthesis till ripening. An attempt to promote parthenocarpic receptacle developmentwith 4-(indole-3-) butyric acid after the removal of all carpelsbefore pollination was unsuccessful. It was concluded that theactive growth substances probably stimulated growth initiallyin the tissues of the unpollinated carpels, which in turn promotedthe development of the receptacle.     

The competence to acquire cellular desiccation tolerance is independent of seed morphological development.

Acquisition of desiccation tolerance and the related changes at the cellular level in wheat (Triticum aestivum cv. Priokskaya) kernels during normal development and premature drying on the ear were studied using a spin probe technique and low temperature scanning electron microscopy. During normal development, the ability of embryos to germinate after rapid drying and rehydration was acquired after completion of morphological development, which is a few days before mass maturity. The acquisition of desiccation tolerance, as assessed by germination, was associated with an upsurge in cytoplasmic viscosity, the onset of accumulation of protein and oil bodies, and the retention of membrane integrity upon dehydration/rehydration. These features were also used to assess cellular desiccation tolerance in the cases when germination could not occur. Slow premature drying was used to decouple the acquisition of cellular desiccation tolerance from morphogenesis. Upon premature drying of kernels on the ears of plants cut at 5 d after anthesis, desiccation-tolerant dwarf embryos were formed that were able to germinate. When plants were cut at earlier stages poorly developed embryos were formed that were unable to germinate, but cellular desiccation tolerance was nevertheless acquired. In such prematurely dried kernels, peripheral meristematic endosperm cells had already passed through similar physiological and ultrastructural changes associated with the acquisition of cellular desiccation tolerance. It is concluded that despite the apparent strong integration in seed development, desiccation tolerance can be acquired by the meristematic cells in the developing embryo and cambial layer of endosperm, independently of morphological development.     

ADVENTIVE EMBRYOGENESIS IN CITRUS (RUTACEAE) II. POSTFERTILIZATION DEVELOPMENT

Cytological and histological studies on postfertilization development of ovules were carried out in six facultatively apomictic Citrus cultivars. At the time of anthesis, adventive embryo initial cells (AEICs) were detected mainly in the cell layers of the nucellus around the chalazal half of the embryo sac. During the approximately 40 days rest period of the AEICs after fertilization, rapid cell division and enlargement in the endosperm and the chalazal half of the nucellus resulted in the split of AEICs into several separated areas forming the micropylar, lateral and chalazal islands surrounding the enlarging embryo sac. Both in diploid seeds with triploid endosperm and triploid seeds with pentaploid endosperm, the AEICs located in the micropylar half successfully developed into adventive embryos. In diploid seeds, almost all AEICs located in the chalazal half did not develop beyond the initial-celled stage, while in the triploid seeds, those located in the chalazal half occasionally developed into cotyledonary embryos. In seeds with aborted endosperm, the AEICs located in the chalazal half often developed into cotyledonary embryos. The chalazal expiants from normal seeds produced a large number of embryos in vitro. Four results can be summarized from these studies on adventive embryogenesis as follows: 1) All AEICs are initiated prior to anthesis. 2) Whether or not the AEICs successfully developed into adventive embryos is dependent upon their position in the seed. 3) The farther the AEICs are located from the micropylar end, the more adventive embryogenesis is suppressed by endosperm. 4) The degree of adventive embryogenesis in the chalazal half is affected by time and extent of malfunction of the endosperm. Under natural conditions, these regulatory systems of adventive embryogenesis contribute to high production of zygotic seedlings in apomictic Citrus species and cultivars.     

The effect of maleic hydrazide on growth and mutation of a blue-green alga

Summary Maleic hydrazide is mutagenic to the blue-green alga Anacystis nidulans at pH 5.0, producing mutations to streptomycin-resistance and penicillin-resistance, and is non-mutagenic at pH 8.0, promoting growth in low concentrations. The maleic hydrazide-induced increases in the levels of streptomycin- and penicillin-resistance are 1000 and 500 times respectively over the parental strain. The resistant strains can further mutate spontaneously to give rise to strains resistant to still higher concentrations of the antibiotic.Cultures growing with manganese are more sensitive to maleic hydrazide-induced inhibition of growth than are those growing without manganese. However, cultures of the alga in maleic hydrazide grown in the presence of two different concentrations of manganese differ in the extent of growth which is better in those with the higher manganese concentration than in those with the lower. These results suggest different modes of interaction between manganese and maleic hydrazide, controlled primarily by manganese concentration.     

Changes in the rhizosphere microflora of maize seedlings by pretreatment of roots with hormones and urea

Summary Effect of pretreatment of root of maize seedlings with gibberellic acid, maleic hydrazide and urea was investigated. Gibberellic acid at 1 ppm stimulated the growth of fungi, bacteria, and actinomycetes in the rhizosphere region of maize seedlings while at 5 ppm concentration population of bacteria and actinomycetes were suppressed. Maleic hydrazide treatment stimulated all the three groups at 5 ppm concentration but at 1 ppm there was increase in population of only fungi and actinomycetes. Urea stimulated the growth of fungi, bacteria, and actinomycetes. The order of predominance of different groups also changed with treatments. It was fungi > bacteria > actinomycetes in case of gibberellic acid at 1 ppm and 5 ppm and maleic hydrazide at 1 ppm; and bacteria > fungi > actinomycetes in case of maleic hydrazide at 5 ppm, urea at 0.1M and in control.     

The Production of Haploid Wheat Plants via Wheat X Maize Hybridization

The intergeneric cross between wheat and maize are characterized by a high frequency of formation of hybrid embryos, but maize chromosomes are rapidly eliminated in the first few cell division cycles to produce haploid wheat embryos. If left the embryos on the plants they will soon abort, as a result of the absence or poor development of the endosperm. Embryo rescue techniques should not enable these embryos to grow to plants because of the embryos were extremely young for embryo culture. Viable embryos were obtained at much higher frequenc, if spikes containing cross-pollinated florets were dipped in 100 ppm 2,4-D solution 4 hours after pollination. Of the 382 florets treated, 64(16.8%) embryos were obtained 10 days after treatment, and 47 plants recovered on the culture medium. In control (2,4-D not applied) only 1 (0.96%) embryo and 1 plant was obtained from 104 florets. This simplified technique should enable haploid wheat plants production through wheat - maize to apply to practical breeding.     

Embryological Studies on Apomixis in Pennisetum squamulatum

Studies on the formation and development of the embryo sac of the apomictic material of Pennisetum squamulatum Fresen indicated that normal archesporial cell did form with consequent development of a megaspore mother cell and later meiotic division to give rise to a triad. But invariably the megaspore mother cell and the triad underwent degeneration after formation. During the period of formation or degeneration of the megaspore or the triad a number of nucellar cells around the degenerated sexual cell became much enlarged. Frequently, one of the enlarging nucellar cells near the micropylar end became vacuolated and then developed into an aposporous uninucleate embryo sac, which underwent two further mitotic divisions to form an aposporous four-nucleate embryo sac, where the four nuclei remained in the micropylar end. Thus in the mature aposporous embryo sac there were one egg cell, one synergid and one central cell (containing two polar nuclei). Antipodal cells were completely lacking. The pattern of development of the aposporous embryo sac resembles the panicum type. There were two types of embryo formed during apomictic development namely ( 1 ) The pre-genesis embryo--embryo formed without fertilization, 1 to 2 days before anthesis, and (2) The late-genesis embryo--derived from the unfertilized egg cells, 3 to 4 days after anthesis. In the late-genesis embryo type, the egg cell divided after the secondary nucleus has undergone division to form the endosperm nuclei. All egg cells developed vacuoles before they differentiated into embryos. The development of the aposporous embryo followed the sequence of the formation of globular, pearshaped embryo and full stages of differentiation. The unfertilized secondary nucleus divides to form free endosperm nuclei after being stimulated by pollination. The development of the endosperm belongs to the nuclear-type.     

Pseudogamous Apomixis in Maize and Sorghum in Diploid-Tetraploid Crosses

Apomictic seed development is a complex process including formation of unreduced embryo sac, parthenogenetic embryo development from the egg cell, and endosperm formation either autonomously, or due to fertilization of polar nuclei by the sperm (under pseudogamous form of apomixis). In the latter case, an obstacle to the normal endosperm development is disturbance of maternal (m) -to-paternal (p) genomic ratio 2m: 1p that occurs in the cases of pollination of unreduced embryo sac with haploid sperms. Usage of tetraploid pollinators can overcome this problem because in such crosses maternal-to-paternal genomic ratio is 4m: 2p that provides formation of kernels with plump endosperm. Using tetraploid lines as pollen parents we observed formation of plump kernels on the ears and panicles of diploid maize and sorghum accessions. These kernels had hybrid endosperm and diploid maternaltype embryo or hybrid embryo with different ploidy level (2n, 3n, 4n). The frequencies of plump kernels on the ear ranged from 0.2-0.3% to 5.7-6.2% counting from the number of ovaries. Maternal-type plants were found in two maize lines, their frequency varying from 10.7 to 37.5% of the progeny plants. In CMS-lines of sorghum pollinated with tetraploid sorghum accessions, the frequency of plump kernels ranged from 0.6 to 14.0% counting from the number of ovaries; the frequency of maternal-type plants varied from 33.0 up to 96.1%. The hybrid nature of endosperm of the kernels that gave rise to maternal-type plants has been proved by marker gene expression and by SDS-electrophoresis of endosperm proteins. These data testify to variable modes of seed formation under diploid × tetraploid crosses in maize and sorghum both by amphi- and by apomixis. Therefore, usage of tetraploid pollinators might be a promising approach for isolation of apomixis in maize and sorghum accessions.     

侧金盏胚和胚乳发育的细胞胚胎学研究

利用石蜡切片技术对毛茛科植物侧金盏胚及胚乳发育进行了研究,以明确其胚胎发育的特征,为毛茛科植物的系统研究提供资料。结果表明:(1)侧金盏胚的发育属于柳叶菜型,胚乳发育为核型;初生胚乳核的分裂早于合子的第一次分裂。(2)种子成熟时,种胚尚未分化完全,尚处于球形胚后期或心形胚早期阶段,整个胚发育大约需要50~60d。(3)侧金盏种子存在明显的形态生理休眠现象,经后熟作用逐渐完成种胚的分化与生长,形成子叶形胚;侧金盏种子在相同处理条件下胚分化和发育的速度存在差异。     

Cytokinin Activity in Lupinus albus L: IV. Distribution in Seeds

Endogenous levels of cytokinin activity were examined in Lupinus albus L. seed at intervals of 2 weeks after anthesis using the soybean callus bioassay. High levels of cytokinin activity per gram seed material were present in the seeds at 2, 4, and 6 weeks after anthesis. The cytokinin activity per gram seed material was low at 8 and 10 weeks after anthesis. Cytokinin activity associated with each seed was greatest at 6 weeks after anthesis. The majority of the activity in the seeds at 4, 6, and 8 weeks after anthesis was in the endosperm. Cytokinin activity was also detected in the testas and embryos at 4, 6, 8, and 10 weeks, and the suspensors at 4 weeks. Column chromatography of extracts of the different seed fractions on Sephadex LH-20 indicated that the cytokinins present coeluted with zeatin, zeatin riboside, and the glucoside cytokinins. It is suggested that cytokinins are accumulated in the seeds and are stored in the endosperm mainly in the form of ribosides and glucosides of zeatin. The reduction in cytokinin activity in the seed coincides with the reduction in endosperm volume and embryo growth and suggests that these compounds are utilized during the course of seed maturation.     

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.     

Development of fertilized ovules and their role in the growth of the pea pod

The histological development of fertilized ovules during fruit-set and development in pea ( Pisum sativum L. cv. Alaska) has been investigated. Killing the ovules on day 0 (anthesis) or day 1 prevented fruit-set and resulted in ovary degeneration. When the ovules were destroyed at later stages the ovaries developed, though the rate of growth of the pod was reduced significantly. Pollination in pea occurs normally the day before anthesis, and fertilization of the egg cell 32 to 48 h later. The first divisions of the zygote and endosperm nuclei started simultaneously (ca 48 h after pollination) but the endosperm developed more rapidly than the embryo; the embryo sac cavity was lined with free endosperm nuclei at the time of beginning suspensor elongation. Extracts of endosperm and ovule coats from ovules at day 7 after anthesis showed fruit-set activity in pea, the latter material having about 3 times more activity than the former per ovule basis. These results indicate that fertilization of the ovule is necessary for fruit-set in pea, and that compounds which induce fruit-set are probably synthesized in the ovules following fertilization.     

Embryology and fruit development in four species of Pistacia L. (Anacardiaceae)

Pistacia atlantica, P. palaestina, P. lentiscus and P. saportae , were found to have great similarity in their embryology and fruit development. The anatropous, pendulous and crassinucellate ovule was initially unitegmic; later, the integument split close to the micropyle, forming a partial second integument. After anthesis there was a development of a hypostase and an obturator. The development of the Polygonum-type embryo sac followed division of a megaspore mother cell, giving a tetrad or triad of megaspores. The functional megaspore was the chalazal one. The ovary developed into a mature pericarp after anthesis, even when pollination was prevented, and before the zygote divided. Therefore, the fruit can be parthenocarpic. The ovule started to grow after initiation of embryo development until it filled the cavity within the pericarp. The zygotes were dormant for 4–18 weeks after pollination. In P. saportae reproduction became arrested during the development of the embryo sac; only very few abnormal embryos were found. No fixed pattern of embryo development could be discerned. The endosperm was initially nuclear, becoming cellular when the embryo started to develop. The seed coat was derived from the integument and the remnants of the nucellus.     

Plant regeneration through somatic embryogenesis in Quercus suber

Cork oak ( Quercus suber L.) zygotic embryos, endosperm and ovules were treated with different concentrations of 2,4-D for induction of somatic embryos. Plant material was collected during the embryo development season, from June to September. Immature embryos proved to be the most reactive initial explant. Callus and somatic embryos developed a few weeks after the beginning of the 2,4-D treatment. For embryo development experiments, different growth regulators and cold and desiccation treatments were tested. Cold storage of somatic embryos matured in vitro at 5°C was the best treatment for breaking dormancy.     

Effect of β-indoleacetic acid,maleic hydrazide,and 2,3,5-triiodobenzoic acid on N,P, K,and Ca accumulation by pea plants

A study was performed on the effect of various concentrations of IAA, 2,3,6-triiodobenzoic acid, and maleic hydrazide, supplied to Richter’s nutrient solution, on growth of pea plants in water cultures. After a 18-day cultivation growth was evaluated and in the plants gathered the content of total N, P, K, and Ca was estimated. Growth of experimental plants (as evaluated from fresh and dry weight) was affected by all three regulators in dependence on the concentration used. It was stimulated by lower concentrations and inhibited by higher, the production of both fresh and dry weight of the root system being stimulated by all IAA concentrations used. The ratio of root dry weight to that of the entire plant was markedly increased after application of IAA and 2,3,5-triiodobenzoic acid, whereas when applying maleic hydrazide it was only slightly increased in comparison with control. Stimulation or inhibition of growth induced by IAA treatment was accompanied by an accordingly increased or decreased accumulation of N, P, K, and Ca. Thus their utilization did not change in comparison with control. On the other hand, both inhibitory and stimulatory effects of 2,3,5-triiodobenzoic acid and maleic hydrazide on growth were associated with a relatively lower accumulation of the elements in question, resulting in an increased utilization. The distribution index of N, P, K, and Ca decreased with increasing concentrations of IAA, 2,3,5-triiodobenzoic acid and maleic hydrazide. Only the highest 2,3,5-triiodobenzoic acid and maleic hydrazide concentrations used brought about a more marked increase in the distribution index of potassium, simultaneously with a marked decrease in the distribution index of calcium.     

Developmental Changes in the Free Amino Acid Pool of Rice(Oryza sativa L. subsp,japonica) Bmbryos

The level of/various amino acids in rice embryos rose sharply during embryo differentiation (7–9 days after anthesis). Then it increased steadily or tended to become stable at mid-maturation stage (13–18 days after anthesis), thereafter continuing to increase, except that the contents of aspartate and glutamate decreased significantly. The total free amino acid pool expanded rapidly during the differential stage. There after the pool capacity showed only a slightly increase until the end of embryogenesis. Both on embryo cell and dry weight bases, the capacity reached the maximum at the 9th day after anthesis, then decreased at the 13th day, and later remained stable. We deemed that the establishment of the free amino acid pool is one of the events which occur in the process of rice embryo differentiation. By the fulfillment of the differentiation (the 13th dray after anthesis), the pool capacity within the embryo cells remained stable on the whole. The free amino acid pool was dominated by serine, alanine, aspartate and glutamate during the differentiation stage. In the maturation stage, serine, alanine, arginine and lysine were the main components. These predominant; amino acids may play an important role in regulating the availability of the whole amino acid pool.