EFFECT OF GROWTH RATE,MORPHOGENIC ACTIVITY,AND PHYLOGENY ON SHOOT APICAL ULTRASTRUCTURE IN OPUNTIA POLYACANTHA (CACTACEAE)

Dormant short shoot apices of Opuntia polyacantha were cultured under three conditions: cytokinin and high sucrose to stimulate the formation and rapid growth of a leafy long shoot; cytokinin and no sucrose (slow growth of a leafy long shoot); gibberellic acid and high sucrose (rapid growth of a spiny short shoot). These meristems, and also dormant (uncultured) ones, were analyzed by stereological, ultrastructural techniques. By comparing meristems growing with cytokinin but with or without sucrose, correlations between metabolic rate and apical ultrastructure were studied; comparison of leaf-producing and spine-producing meristems permitted examination of correlations with morphogenic role; comparison with published data for four other species permitted study of phylogenetic effects, and comparison with dormant apices revealed information about meristem activation. Ultrastructure varied according to each condition: metabolic rate, morphogenic activity and species can be distinguished by quantitative methods. Apical ultrastructure is most strongly correlated with rate of growth such that apices of differing species resemble each other if growing at similar rates, whereas apices of a single species differ markedly if growing at differing rates or if performing different morphogenic activities. Hyaloplasm is an excellent indicator of metabolic rate; mitochondria, nuclei, and vacuoles are not.     

CYTOKININ- AND GIBBERELLIC ACID-INDUCED EFFECTS ON THE DETERMINATION AND MORPHOGENESIS OF LEAF PRIMORDIA IN OPUNTIA POLYACANTHA (CACTACEAE)

Cytokinins and gibberellins are able to strongly influence the development of “leaf” primordia in the cactus Opuntia polyacantha. Under the influence of cytokinin, the primordia produced by cultured axillary bud apical meristems develop as normal, photosynthetic leaves, being composed of regular epidermal cells, guard cells, mesophyll and mucilage cells as well as vascular tissue. Under the influence of gibberellic acid (GA), the primordia develop as cactus spines, composed of thick-walled epidermal and fiber cells. Guard cells, vascular tissue and parenchyma do not occur. Thus GA is able to redirect leaf morphogenesis in O. polyacantha far more completely than has been reported for other plants. The mitotic activity of the primordia that will develop into spines is significantly higher (at the 5 % level) than the mitotic activity of the primordia that will develop into leaves. This is interpreted to indicate that the primordia are either leaf primordia or spine primordia from a very early age, and possibly are never uncommitted or undetermined primordia, as has been suggested for fern leaf primordia.     

CYTOKININ- AND GIBBERELLIC ACID-INDUCED EFFECTS ON THE STRUCTURE AND METABOLISM OF SHOOT APICAL MERISTEMS IN OPUNTIA POLYACANTHA (CACTACEAE)

The dormant axillary buds of Opuntia polyacantha can be activated by either cytokinins or gibberellic acid. Under the influence of benzylaminopurine (BAP), the axillary bud meristem increases greatly in size and becomes mitotically active. The primordia produced by the meristem develop as normal photosynthetic leaves. Gibberellic acid (GA) also causes the meristem to become mitotically active, but the meristem does not increase in size. The primordia produced under the influence of GA develop as normal cactus spines. Leaf-producing meristems and spine-producing meristems have the same zonation, despite the differences in size. The meristems are composed of a uniseriate tunica, a central mother cell zone, peripheral zone, and a pith rib meristem. The mitotic activity of each of the zones in the leaf-producing meristem differs significantly from the mitotic activity of the corresponding zones in the spine-producing meristem.     

THE FUNCTION OF EXTRAFLORAL NECTARIES IN OPUNTIA ACANTHOCARPA (CACTACEAE)

Opuntia acanthocarpa (Cactaceae) possesses extrafloral nectaries embedded in the areoles of new reproductive and vegetative growth. The nectar secreted by these glands attracts ants and is a nutritional food source. Members of one attracted ant species, Crematogaster opuntiae (Myrmicinae), are aggressive and efficient defenders of the plants against cactus-feeding insects. The results of our study are consistent with the ant-guard hypothesis for the role of extrafloral nectaries in O. acanthocarpa. Additionally, individuals of O. acanthocarpa are well protected in comparison with those of O. phaeacantha. The latter generally possess ephemeral extrafloral nectaries and consistently maintain fewer ants.     

SEEDLING DEVELOPMENT OF OPUNTIA BRADTIANA (CACTACEAE)

Seedling development in Opuntia bradtiana, a north-central Mexican endemic, is similar to that of other opuntias, except for the absence of glochids and the fact that germination is extremely slow and germination percentage low. Hypocotyl and root elongation and epicotyl development are rapid for two weeks after rupture of the seed coat. However at this point hypocotyl elongation nearly ceases, while stem and root development continue at a reduced rate. An eight-month seedling is usually not more than 25 mm tall but has numerous areoles with spines and occasionally one subtending leaf. At this time tubercles have begun to coalesce into the vertical rows of ribs characteristic of the section Grusonia.     

PHYSIOLOGICAL RESPONSES TO RAINFALL IN OPUNTIA BASILARIS (CACTACEAE)

An immediate, marked response to small amounts of rainfall occurs in Opuntia basilaris, despite previous drought conditions. The effect of rainfall is upon plant water potential, which is the single most important parameter influencing stomatal opening, CO₂ assimilation, and organic acid synthesis. Nocturnal stomatal opening is initiated following rainfall, and stomata remain open during the daytime. Decreasing stomatal and mesophyll resistances correlate with increasing rates of nocturnal assimilation of ¹⁴CO₂. Photosynthetic rates of ¹⁴CO₂ assimilation are low, despite high plant water potentials and low stomatal diffusion resistances. The decreased mesophyll resistances and increased rates of nocturnal ¹⁴CO₂ assimilation correlate with the increases of nocturnal efficiency of water use and CO₂ assimilation. The diurnal efficiency of water use and CO₂ assimilation is lower than the nocturnal gas exchange efficiency values.     

ROOT GLOCHIDS AND ROOT SPURS OF OPUNTIA ARENARIA (CACTACEAE)

Root glochids of Opuntia arenaria Engelm. are produced by adventitious buds (areoles) that arise endogenously on fleshy roots. If they remain active, root areoles become dwarf shoots that initiate only glochids and trichomes unless the roots are uncovered or the shoots bearing the roots are removed. Then they will expand, producing aerial shoot joints. Root spurs are formed in great numbers on the profusely branched system of small roots. They consist of clusters of rootlets about one mm long that are initiated in sympodial sequence, each new rootlet arising endogenously near the base of the preceding one. On older spurs this results in the formation of a short axial peg. Rootlet primordia lack a root cap from the beginning and appear to mature quickly, losing all their meristematic characteristics and becoming completely covered with root hairs, even over the tip. They may represent a mechanism for the rapid production of root hairs during the infrequent periods when moisture is available. In any case, they seem to be transitory structures because cork soon forms beneath the older ones on a spur.     

BIOMECHANICS OF CLADODES AND CLADODE-CLADODE JUNCTIONS FOR OPUNTIA FICUS-INDICA (CACTACEAE)

Shoots of Opuntia ficus-indica (L.) Miller consist of a sequence of flattened stem segments (cladodes) in contact over only a small portion of their periphery. The maximum angular deflection for an upper terminal cladode under a weight equal to its own fresh mass applied perpendicular to its face increased from 5° to 9° as cladode length increased from 20 cm to 60 cm, consistent with an increase in mass proportional to length^2.83. Just over half of the angular deflection of an upper cladode represented flexure of the cladode-cladode junction; the angular deflections averaged fourfold more for mass loadings perpendicular to the cladode face compared with those parallel to it. Compared with such static loading by mass, dynamic loading by wind for a 31-cm-long cladode led to a maximum angular deflection of only 0.13° at a wind speed of 1 m sec⁻¹ and 2.3° at 10 m sec⁻¹. Drought caused the angular deflections to increase 9% for 21-cm-long cladodes over a 90-day period and to decrease 45% for 44-cm-long cladodes. Increases in stem temperature from 0 C to 20 C increased angular deflections of a 27-cm-long cladode about 10%, with little further increase up to 50 C. Even though the cladodes were thin compared with stems of many perennials and the cladode-cladode junction comprised only about 3.5% of their peripheral area, the shoots of O. ficus-indica proved to be quite rigid, as angular deflections of cladodes were only slightly influenced by temperature and wind, were not markedly enhanced by drought, and were less than 10° under loading by a cladode's mass.     

HORMONAL CONTROL OF OOCYTE MATURATION IN ARENICOLA MARINA L. (ANNELIDA, POLYCHAETA)

In Arenicola marina (Annelida, Polychaeta) the oocytes are arrested in the first prophase stage of meiosis until spawning. Oocyte maturation is under hormonal control: when incubated in vitro in a brain extract oocytes reach the first metaphase at which they remain arrested until fertilization. The importance of calcium in oocyte maturation has been investigated by using different drugs known to act on membrane calcium permeability and to modify intracellular free calcium concentration. Tetracaine, procaine, D-600, verapamil (Isoptin), propranolol, oxprenolol and lanthanum chloride, calcium deprivation but not ionophore A23187, are all able to induce oocyte maturation. This suggests that the brain hormone may act on the oocyte by regulating, probably increasing, the intracellular free calcium concentration, as it has been proposed for oocytes of other animals. The importance of -SH/-SS- in meiosis reinitiation is suggested by the fact that dithiothreitol and 2, 3-dimercaptopropanol, two disulfide reducing agents, both induce oocyte maturation.     

HORMONAL CONTROL OF PEROXIDASE ACTIVITY IN CULTURED PELARGONIUM PITH

Freshly excised Pelargonium pith tissue lacks peroxidase activity toward guaiacol or benzidine, but it develops such activity within 24–36 hr in aseptic culture. All the activity is manifested as a single enzyme moving toward the cathode during electrophoresis on starch gel at pH 9.0. This development of peroxidase activity is at first (up to ca. 50 hr in culture) inhibited and later (ca. 100–150 hr in culture) promoted by IAA. This dual effect of IAA resembles that previously reported for specific isoperoxidases in tobacco pith cells. Kinetin alone also inhibits peroxidase formation, but in the presence of IAA those concentrations which enhance growth enhance peroxidase formation as well.     

红铃虫生殖的激素调节控制

不同时期加温催化的红铃虫越冬代雌蛾,其卵巢的发育程度及速度是明显不同的,而卵巢的发育与否似乎又与其交配能力相关。4月上旬刚羽化的雌蛾卵巢小而透明,没有任何卵巢沉积,以后几天的发育甚微,而此时的交配率仅为13%左右。到8月初,刚羽化的雌蛾卵巢已部分发育,末端卵粒已有少量卵黄沉积,其发育速度也较前者快,而此时的交配率已上升至49%左右。 经ZR515点滴的刚羽化雌蛾(无论是什么时期加温催化的),它们的卵巢发育程度和速度均显著提高,并促进了卵黄沉积。因而,它们的交配能力也随之增强。经最适剂量0.1μg/头点滴的雌蛾,交配率可高达70%。 经点滴的雌蛾产卵周期和产卵高峰均大大提前,卵母细胞的成熟比较一致,因而每次均能产出成批的卵,总产卵量也明显高于对照。并且,这些卵均能孵化,胚后发育亦属正常。 本文还探讨了激素、卵巢以及交配等三者的相互关系,并试论了补充营养、激素对交配及产卵的作用。     

ENVIRONMENTAL AND HORMONAL CONTROL OF TURION GERMINATION IN MYRIOPHYLLUM VERTICILLATUM

Germination, or outgrowth, of Myriophyllum verticillatum turions involves a series of visible changes starting with reflexing of leaves followed by extension and curving of the axis, and then by root formation. Before abscission, turions grow out in response to long days (16 hr) but not short days (8 hr). After abscission, turions show maximal dormancy which can be fully broken by a cold treatment (4 C). Turions are heterogeneous in degree of dormancy and ability to respond to less complete dormancy-breaking treatments, e.g., long days at 20 C. Cytokinins (10^-6 m) break dormancy of non-cold-treated turions, whereas gibberellic acid (GA₃) is ineffective except at high concentrations (10^-3 m). Continuous treatment with cytokinins causes abnormal development after germination. GA₃, on the other hand, induces apparently normal development even at high concentration. Indoleacetic acid (IAA) induces outgrowth only at high concentrations (10^-3 - 10^-4 m), but these concentrations also produce abnormal development. Abscisic acid (ABA, 10^-5 m) retards outgrowth of cold-treated turions and can completely suppress it in non-cold-treated turions. The activity of ABA-like substances in turions remains about the same before and during germination, whereas other (unidentified) acidic inhibitors decrease markedly. The cytokinin activity changes in a complex pattern.     

DICHOTOMOUS BRANCHING IN MAMMILLARIA (CACTACEAE)

Cruciate dichotomous branching is a regular phenomenon in at least two species of cacti: Mammillaria perbella and M. parkinsonii, and there is exomorphic evidence that it occurs in other species of this genus. The specimens examined showed no obvious changes in the phyllotaxy of the two shanks derived by dichotomy. In the ecologically and morphologically specialized Cactaceae, it is quite unlikely that dichotomous branching represents the retention of a primitive character. It is furthermore improbable that it is of taxonomic value above the species level.     

HORMONAL CONTROL OF ROOT GROWTH I

The growth of the primary root of a single gene dwarf mutantof Zea mays L., dwarf-1, is dependent upon gibberellic acidor one of its derivatives as a growth hormone. Moreover, forthe root to respond to gibberellin treatment both embryonicand mature tissues must contribute growth stimuli. ¹ This study was financed by the National Institute of Health,Grant GM 08706-03.     

HORMONAL CONTROL OF THE VITELLOGENESIS IN THE JAPANESE OAK SILKWORM, ANTHERAEA YAMAMAZ (LEPIDOPTERA: SATURNIIDAE)

Abstract Effects of ecdysteroid and juvenile hormone (JH) on vitellogenesis of the Japanese oak silkworm, Antheraea yamami are reported in this article. After topical treatment with 20-hydroxyecdysone alone or JH analog (i.e. methoprene) alone and combined treatment with these two chemicals, vitellogenin (Vg) titers in the fat body and haemolymph at the pupal stage were mostly higher than those of the control, indicating that both ecdysteroid and JH exerted a promoting effect on the synthesis of Vg. In contrast, the Vg uptake was markedly inhibited by JH while stimulating effect of the ecdysteroid could be shown that vitellin (Vt) titer in the ovary was lower after methoprene treatments, but higher after 20-hydroxyecdyson treatments. Meanwhile, effects of these two hormones on Vg synthesis in the fat body were also tested with the incubation in vitro with Grace medium containing H-leucine and the hormones. The results demonstrated that Vg synthesis was stimulated after treating with methoprene alone or 20-hydroxyecdysone alone and combined treating with these two chemicals, and particularly ecdysteroid had more marked positive effect. To comprehensively concluded our results, it could be regarded that ecdysteroid play the main role in the regulation of vitellogenesis for the Japanese oak silkworm.     

天蚕卵黄发生的激素调控

报告了蜕皮激素和保幼激素对天蚕Antheraea yamamai卵黄发生的调控作用。当单独以20－羟基蜕皮酮或保幼激素类似物methoprene处理,以及同时用这两种激素处理天蚕蛹时,蛹期脂肪体和血淋巴中卵黄原蛋白（Vg)含量明显高于对照,即二对Vg的合成起促进作用。然而,卵巢中卵黄蛋白（Vt)含量则因激素种类而异,以保幼激素处理时明显低于对照,以20－羟基蜕皮酮处理则反之,即前抑制卵巢对Vg的摄取,而后则起促进作用。离体培养脂肪体并以激素处理的结果表明,20－羟基蜕皮酮和methoprene均能促进Vg合成,但前作用更。综合考虑上述结果可以认为蜕皮激素对该蚕的卵黄发生起主要调控作用。     

HORMONAL CONTROL OF TRANSLOCATION OF PHOTOSYNTHETICALLY ASSIMILATED 14C IN YOUNG SOYBEAN PLANTS

The normal supply of growth substances to a young soybean plant was altered by removing the plant's apical meristem and replacing this meristem with an aqueous solution of either indole-3-acetic acid (IAA), gibberellic acid (GA), or water. The length of each experiment was 1 hr. In the middle of it, ¹⁴CO₂ was administered to one of the primary leaves of the plant, and at the end distribution of ¹⁴C in various parts of the plant was determined. It was found that an addition of growth substances stimulated translocation in three different ways. Both IAA and GA increased the total amounts of sucrose-¹⁴C translocated, increased the rate of its translocation, and affected the distribution pattern of translocated sucrose throughout the plant. Experiments using IAA-¹⁴C have shown that the action of IAA is on the longitudinal translocation in the stem and not on the transfer of photosynthate from the mesophyll to the conducting tissues of the leaf.     

HORMONAL CONTROL OF REVERSIBLE DEGENERATION OF FLIGHT MUSCLE IN THE COLORADO POTATO BEETLE, LEPTINOTARSA DECEMLINEATA SAY (COLEOPTERA)

In the hibernating (diapausing) Colorado potato beetle, Leptinotarsa decemlineata Say, the flight muscles show pronounced degeneration. The muscle fibrils are greatly reduced in diameter and the sarcosomes are virtually absent. Similar signs of degeneration could be produced by extirpation of the postcerebral complex of endocrine glands, the corpora cardiaca and corpora allata. Reimplantation of active postcerebral complexes resulted in a very rapid regeneration of the muscle fibrils and new formation of sarcosomes.     

THE ULTRASTRUCTURE OF DEVELOPING LATEX DUCTS IN MAMMILLARIA HEYDERI (CACTACEAE)

Electron microscopy was used to investigate early development of latex ducts in Mammillaria heyderi (Cactaceae). Numerous vesicles (secondary vacuoles) form from invaginations of the plasmalemma near sites of wall thinning, from endoplasmic reticulum (ER), and from vesiculate grana of degenerate plastids. Dictyosomes, though they occur in young duct cells, do not seem to be responsible for the formation of vesicles. Cytoplasmic vesicles may contain fibrillar, globular, or crystalline materials, or may be devoid of any type of particulate matter. They may be responsible for storage of numerous laticiferous components. Lysosomal materials could be stored in some vesicles and contribute to the degradation of the protoplast. Some nuclei contain condensed chromatin and are subject to deformation and collapse. Mitochondria and lipid bodies are common in young duct cells but ER is rare. When ducts form in young tissues, plastids in the lumen do not produce starch grains or extensive membranous networks. The plastids eventually degenerate to become a part of latex. If ducts form in older, established tissues having mature plastids, the plastids undergo extreme modification.