RADIATION DAMAGE IN SHOOT APICES OF CONCORD GRAPE

Pratt , Charlotte . (N. Y. State Agri. Expt. Sta., Geneva.) Radiation damage in shoot apices of Concord Grape. Amer. Jour. Bot. 46(2) : 103-109. Illus. 1959.—Dormant rooted cuttings of ‘Concord’ grape were exposed either to 200-6000 r of X rays or to 2-6 hr. of thermal neutrons (average total dose of 4.80 × 10¹¹ to 1:59 × 10¹³ neutrons/cm.²). Percentage of plants surviving in the field tended to decrease with dosage beginning with 2000 r of X rays or 2 hr. of thremal neutrons. It showed a sharp drop in lots which had received doses of 4000 r of X rays or 4 hr. of thermal neutrons. Frequency of hudless shoots (shoots lacking a terminal bud after the first leaves emerged) increased with dosage, beginning with groups which had received 2000 r of X rays or 2 hr. of thermal neutrons. Microscopic examination of radiation-damaged shoot apices showed one or more of the following characteristics: (1) shape and organization of the apical meristem different from that of the untreated shoot apex, which is described; (2) no young primordia; (3) acropetal advance of maturation of cells; in 4 cases cells with spirally thickened, lignified walls were found 1-4 cells deep in the meristem; (4) collapse of cells in the tunica and corpus; formation of periderm and deeper, cambium-like divisions below the wound; (5) site of the former apical meristem either carried up on the base of a single terminal leaf or remaining a flat area between terminal leaves. Aspects of radiation sensitivity of the shoot and theories of shoot organization with reference to natural and induced chimeras are discussed.     

THE CONCEPT OF INCIPIENT VASCULAR TISSUE IN FERN APICES

A comparison of shoot apices of runners and rosettes of Nephrolepis with shoot apices of Adiantum indicates that a uniform concept of apical organization can be applied throughout. The region directly below the apical initials is designated a “central zone,” by analogy with that found in Lycopodium. The central zone is regarded as undifferentiated meristematic tissue rather than incipient vascular tissue.     

云南山楂茎尖的离体培养及其无性系快速繁殖

用云南山楂(Crataegus scabrifolia(Franch.)Rehd.)成年树茎尖和实生芽两种不同发育阶段的材料为外殖体,诱导它们休眠芽萌动,丛生芽条并诱导芽条生根。实验结果如下:1.以成年态的云南山楂侧芽为外植体,培养在附加IAA 0.1—0.5mg/l+6-BA 1-2mg/l的MS培养基上可诱导芽的萌发;将芽继代培养在附加0.5—1mg/l 6-BA的SH或MS培养基上,40天后芽数增殖4—6倍;将芽条截下置于1/2MS培养基上,附加不同浓度的IAA或IBA,可得到50—80％的生根率。2.以实生芽为外殖体,在相同条件下,则20天后芽数增殖便可获4—6倍;98％以上生根。结果表明:云南山楂的幼年态要比成年态易脱分化和再分化。     

MODELING OF MERISTEMATIC GROWTH OF ROOT APICES IN A NATURAL COORDINATE SYSTEM

A curvilinear, orthogonal coordinate system, which resembles the pattern of periclines and anticlines in the cellular network of root apices, is presented. The system makes possible an analysis of the dynamics of apical growth: the relationship between growth rates and tensile stresses in cell walls. In this paper the coordinate system is used in modeling the growth and cell partitioning in the apical domes. The symplastic growth is described by means of the growth tensor which is assumed to have diagonal form in the system, so its coordinate lines represent the principal directions of growth rate. The coordinate system and the growth tensor in diagonal form assure temporal stability of form and cellular structure of the modeled apex including transition from the dome to the cylindrical part of the apex. The spatial and temporal aspects of the dome part of two types of root apices—one with maximum of volumetric relative growth rate at the center region of the apex, and another with minimum of the rate (quiescent center)—are described. The maximum of the rate at the center results in the cellular pattern with an apical cell and merophytes, the minimum results in ribs of cells (inside the root proper) converging toward the quiescent center.     

RADIATION DAMAGE IN APPLE SHOOT APICES

Pratt , Charlotte , John Einset , and Mohammad Zahur . (N. Y. S. Agric. Expt. Sta., Geneva.) Radiation damage in apple shoot apices. Amer. Jour. Bot. 46(7): 537–544. Illus. 1959.—Pattern of shoot growth and anatomy of the shoot apex of ‘Golden Delicious’ apple trees on ‘East Malling IX’ rootstock are compared in normal trees and those growing under chronic gamma irradiation (average doses of 17–48 r per 20-hr. day) at Brookhaven National Laboratory. Bud damage in 6 varieties of apple trees is compared. Irradiated ‘Golden Delicious’ formed lateral buds on the current year's shoot, but the following year these buds grew into spurs which failed to form a terminal bud (“budless” spurs) and enlarged to form “club tips” and “swollen spurs” in this and subsequent years. Cells with thick walls and lightly stained cytoplasm occurred in shoot apices of irradiated lateral buds in mid-June. The first tunica layer was more resistant to radiation than the inner tunica layers and the corpus; pith rib meristem was still more resistant. Inflorescence and floral meristems were rarely found, but once formed, continued development. One-year-old budless spurs had a few leaves but neither an organized apical meristem nor leaf primordia. Surface of the apex was often folded. Periderm and, later, deep-lying wound cambium developed. Expansion of pith, vascular tissue, cortex, wound cambium and periderm caused enlargement of club tips and swollen spurs. Many lateral buds from the gamma field which were propagated without irradiation in early August grew into long shoots with terminal buds. Scions removed from irradiation in November and inserted into normal trees showed lower survival and many of their shoots were budless. This suggests that the capacity for normal growth of a bud damaged by chronic irradiation is greater in mid-summer than later in the year. With reference to percentage of budless shoots, ‘Delicious,’ ‘Golden Delicious’ and ‘McIntosh’ were more sensitive to an average dose of 24 r per day and lower doses than were ‘Cox,’ ‘Macoun’ and ‘Spy.’ Symptoms of radiation damage in apple buds during the first year were similar following acute or chronic irradiation. Degree of radiation damage, as expressed by death of apical meristems, was concluded to vary with stage of development of the bud, structure of the apical meristem, and genetic constitution.     

A SURVEY OF THE VEGETATIVE SHOOT APICES IN THE FAMILY MALVACEAE

The present study compares the structure of the vegetative shoot apex in 40 species of the Malvaceae. There is a wide range of size, shape, and zonation within the apices of the family. Although many of the apices are domed, some are flat-topped and do not extend above the axil of the youngest leaf primordium. Also, most of the species investigated are recorded as having a more or less marked cytohistological zonation superimposed on the tunica-corpus configuration. The tunica is single-layered in a majority of species, but stratification of the upper corpus is common. In an effort to give a more accurate concept of apical structure and activity, the apex is described as the metrameristem and its derivatives: the flanking meristem, and the pith rib meristem or pith mother cells. The metrameristem, consisting of the tunica initials and the co pus initials, is the focal point of the study of the zoned apices. Data are presented for the measurements of the metrameristem, measurements of the apical dome, type of flanking meristem, origin of the pith, and growth habit of the plant. There appears to be a correlation between growth habit and the distinctness with which the metrameristem is marked off from the surrounding tissue. Most of the herbaceous species have an indistinctly marked metrameristem, whereas the shrubby trees and trees have a distinctly marked metrameristem. Zonation in shrubs and suffrutescent plants may be of either type.     

A QUANTITATIVE STUDY OF SIEVE-TUBE DIFFERENTIATION IN VEGETATIVE SHOOT APICES OF COLEUS

Quantitative methods, with round-the-clock collecting of large samples in successive years, have uncovered several new phenomena of sieve-tube differentiation in young leaves of Coleus vegetative shoots. In small leaves (1–350 μ), there are no sieve tubes in the leaf itself, but they differentiate acropetally in the two traces to each leaf. Regression lines fitted to the data for leaf length vs. most distal position of sieve tubes in the traces support the view that differentiation is steady and acropetal, but they also reveal that differentiation in the traces falls steadily farther behind elongation of the leaf. Leaves more than 500 μ long have sieve tubes close to their tips. An intensive search of leaves of intermediate lengths revealed an isolated locus of sieve-tube differentiation. These relationships were reproducible year after year. Every plant with discontinuous strands of sieve tubes in the second leaf pair had discontinuous xylem in the third. This isolated locus was not seen before, probably because of small samples and daytime collections; most of our cases were from night collections.     

籼稻原生质体培养和植株再生

用籼稻IR52、IR8和IR45的幼花序和幼胚愈伤组织在LS培养基建立了稳定的悬浮培养物。悬浮系的建立经历三个阶段:褐变期,长根期,成熟期。建立了适合籼稻原生质体生长的Y8培养基,其植板率显著高于KPR和PCM培养基。悬浮细胞系间差异明显,只有部份系可以提供有分裂能力的原生质体或具看护活性。以上三个品种的原生质体均分裂良好,但只有IR52和IR8分化出苗,其中IR52分化率1.25%,得再生植株50余株,移至田间生长结实正常。     

FLOODWATER TEMPERATURE AND STEM LENTICEL HYPERTROPHY IN MANGIFERA INDICA (ANACARDIACEAE)

One-year-old seedling trees of Mangifera indica L. cv. Peach were exposed to floodwater temperatures of 15, 22.5, or 30 C for at least 13 days. Immediately prior to flooding, and at daily intervals thereafter, trees were visually examined for evidence of lenticel hypertrophy. Although lenticel hypertrophy was first apparent after 5 days of submergence at 30 C, and after 6 days at 22.5 C, the mean number of days of flooding until lenticel hypertrophy was first observed was 6.6 and 8.1 for the 30 and 22.5 C treatments, respectively. Even after 28 days, lenticel hypertrophy did not occur on plants flooded at 15 C. Initial stages of lenticel hypertrophy were characterized by development of intercellular spaces in the phellem and production of additional phellem tissue by increased phellogen activity. Later stages of hypertrophy were characterized by development of intercellular spaces in the phellem and cortex. Tree survival was not affected by floodwater temperature or lenticel hypertrophy.     

SYSTEMATIC SIGNIFICANCE OF SEED-SURFACE FEATURES IN ORTHOCARPUS (SCROPHULARIACEAE—SUBTRIBE CASTILLEJINAE)

Scanning electron microscope and light microscope examination of seed-coat features of 26 species of Orthocarpus have allowed recognition of many species-level differences (summarized in a key) and of three seed-coat types that parallel taxonomic subgroups but support realignments at generic and infrageneric levels. Type 1 seeds (subg. Orthocarpus, sect. Orthocarpus) have a lateral hilum, sculptured inner tangential seed-coat walls, and a tightly fitting outer seed coat. They are very similar to seeds of Cordylanthus. Seeds of Types 2 and 3 have a terminal hilum and membranous inner tangential cell walls. Type 2 seeds (subg. Orthocarpus, sects. Castillejoides and Cordylanthoides, with one exception) have a net-like, loosely fitting outer seed coat that shows close relationship to seeds of Castilleja. Inner tangential walls of Type 2 seeds normally rupture. Type 3 seeds (subg. Triphysaria, with two exceptions) have a tightly fitting outer seed coat and inner tangential walls are always retained. Seed features support evidence from floral morphology and chromosome numbers that Orthocarpus as currently recognized is not a monophyletic lineage.     

足月新生儿瞬态诱发耳声发射(TEOAEs)的反应特性

取样115例足月儿(230耳),在围产临床条件下提出足月新生儿TEOAEs参量分析1.足月儿(230耳)TEOAEs反应强度平均值为19.999±5.133dBSPLpe,左右耳差异非常显著(P=0.010);2.足月儿(230耳)TEOAEs噪声平均值11.10±2.78dBSPLpe;3.足月儿TEOAEs频域内(0.8～4.0kHz)反应再生率(%),除2.4与4.0kHz频段无显著性差异外(P＞0.05),其余频段均见非常显著性差异(P=0.000);4.足月儿TEOAEs频域内(0.8～4.0kHz)信噪比,除2.4与4.0kHz频段无显著性差异(P＞0.05)外,其余频段均见非常显著性差异(P=0.000);5.足月儿TEOAEs强度与TEOAEs信号、噪声、再生率、频段内信噪比及噪声排斥水平均呈不同程度的相关.     

黑蚱蝉(Cryptotympana atrata Fabricius)鸣声的波谱特征

本文研究了双气囊黑蚱蝉的Click声、自鸣声和群鸣声.其鸣声波形兼有调幅与鸣声主频变化特征.1.Click声主峰频率分布在2.64—5.73KHz之间.2.自鸣声主峰频率在3.6—6KHz之间,比Click声的分布宽度略窄.3.群鸣声的主峰频率分布在4—7KHz范围内.     

ULTRASTRUCTURAL FEATURES OF MITOSIS IN PLOEOTIA COSTATA (HETERONEMATALES,EUGLENOPHYTA)1

The ultrastructural features of mitosis in the colorless phagotrophic euglenoid, Ploeotia costata (Farmer and Triemer 1988bn; syn: Serpenomonas costata, Triemer 1986) are described. During interphase the nucleus is rounded and lies adjacent to the reservoir and the four basal bodies, two of which bear flagella. At the onset of mitosis, two additional flagella are generated from the accessory basal bodies such that four basal bodies with flagella now lie at one pole of the prophase nucleus. Microtubules develop in the nucleus prior to migration of one of the basal body pairs to the opposite pole of the nucleus. By metaphase, chromosomes with layered kinetochores are aligned on the equator of the spindle, and a dumbbellshaped nucleolus stretches from pole to pole. Continued elongation of the nucleus results in the separation of the chromosomal masses at anaphase. The distance between the nuclear poles from metaphase to anaphase changes little although the overall length of the nucleus nearly doubles. By telophase a large interzonal spindle develops between the forming daughter nuclei. The extended interzonal spindle breaks near the center prior to cell cleavage.