Dwarf Shoots Research Articles

Auxin Oxidizing Systems and Ascorbic Acid Turnover in Relation to Physiology of Dwarfism in Sorghum bicolor (L.) Moench

Summary Shoots of dark and light grown seedlings of dwarf, normal and tall sorghum plants were analysed for growth, peroxidase, IAA1) oxidase and ascorbate turnover rate. The manifestation of dwarfism with respect to these parameters except ascorbic acid, was more clear in light than in dark i.e., the activity of IAA oxidase, peroxidase and ascorbic acid utilizing enzymes (collectively as AAU) remained at a remarkably higher level in tall, intermediate in normal and considerably lower level in dwarf shoots. The role of these parameters in relation to physiology of dwarfism is discussed.

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.

Gibberelline in sprossen von Busch- und stangenbohnen

Summary The free acid gibberellins in extracts from young second internodes of dwarf and tall Phaseolus vulgaris seedlings were bioassayed with the tall pea assay. Tall plants contain more gibberellin-like substances than dwarf ones; amounts found correspond with fresh-weights of extracted internodes. Since dwarfs grow like tails after application of a bean gibberellin, it is concluded, that the low gibberellin-content of dwarf shoots is the cause and not the consequence of dwarfism in beans. The gibberellin deficit of the dwarf shoot seems to be the consequence of the low gibberellin content in cotyledons of dwarfs, which was found by Goto and Esashi .

Shoot Apex Development and Rooting of Pinus strobus L. by Dwarf Shoots1

Abstract Foliar applications of benzyladenine (BA) increased bud development of dwarf shoots of Pinus strobus L. When compared to dikegulac-sodium (Atrinal), pyranybenzyladenine (PBA), gibberellic acid (GA3), or pinching. Differences in rate of application of BA were not significant. Vegetative propagation of dwarf shoots varied between individual clones and between years.

Prepinus parlinensis, Sp. Nov., from the Late Cretaceous of New Jersey

Two coniferous dwarf shoots from the Raritan Formation (Late Cretaceous) of Parlin, New Jersey, represent a new species of the extinct pinacean genus Prepinus. Prepinus parlinensis, sp. nov., has a much reduced axis bearing a terminal cluster of 25 or more helically disposed needle leaves. Numerous imbricate cataphylls occur below the cluster of needles and entirely surround the dwarf shoot axis. The fossils are well preserved and are compared with the dwarf shoots and needles of some extant members of the Pinaceae. Of the five previously described species of Prepinus, P. delawarensis Penny is most similar to the new species.

Development of long-shoot terminal buds of western white pine (Pinus monticola)

Long-shoot terminal bud (LSTB) development in western white pine (Pinus monticola Dougl.) was studied throughout the annual growth cycle to determine the phenology of LSTB development and the time of cone-bud differentiation. Development of LSTB began in early April and cataphylls were initiated from mid-August until early November. Cataphyll initiation was slow during May and June when shoots were elongating and then rapid just after shoot elongation was completed. Proximal cataphylls were sterile, whereas more distal cataphylls began to initiate axillary buds by late June or early July. Axillary buds were initiated first in the proximal portions of the LSTB and then acropetally in rapid succession. The last cataphylls to be initiated in the fall remained as sterile bud scales enclosing the LSTB apex. Axillary buds initiated sterile cataphylls which functioned as bud scales. The number varied with the type of axillary bud. Proximal axillary buds initiated few cataphylls and began to differentiate into dwarf shoots or pollen cones in August. The more distal axillary buds differentiated into dwarf shoots during September and October, The most distal axillary buds initiated many cataphylls during September and October but did not differentiate into seed-cone buds or lateral branch buds until after winter dormancy. Consequently, attempts to induce or enhance seed-cone production in P. monticola would probably be most successful in the spring when seed-cone buds differentiate. LSTB bearing seed cones were larger, had broader apices, and produced more cataphylls during the growing season than did LSTB bearing pollen cones. The phenology of LSTB development in soft pines and hard pines is discussed in relation to reports available on the association of cone crops and climatic conditions in several species of Pinus.

Organogenesis in vitro cultures of embryonic shoots ofAbies balsamea (balsam fir)

Embryonic shoots of 15- to 20-year-old Abies balsamea (balsam fir) trees were soaked in (a) water for 15 min or 24 hr and (b) water with 1000 mg per 1 indolebutyric acid (IBA), N-dimethylaminosuccinamic acid (Alar-85), or 1-phenyl-3-methyl-5-pyrazolone (PPZ), singly or in combination with 100 mg per 1 caffeic acid, for 15 min. After the soaking, the embryonic shoots were transferred to a nutrient medium. Nonsoaked (control) embryonic shoots elongated and often formed a basal callus but never showed organogenesis. The soaked embryonic shoots formed new apical buds, with or without bud scales, adventitious dwarf needles or shoots, and root- and embryo-like structures. One of the embryos germinated and formed an irregular shoot. No differences were found between the various soak treatments, except that the 15-min water soak was ineffective. The 24-hr water soak was as effective as the 15-min growth regulator treatments.

Cytokinin Effects Induced in Purple Nutsedge by Perfluidone

Cytokinins break bud dormancy and apical dominance, induce basal bulb formation, and dwarf shoot growth in purple nutsedge (Cyperus rotundusL.). Perfluidone (MBR 8251) [1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl) phenyl] methanesulfonamide] in addition to being phytotoxic, mimics the cytokinins in these aspects. This and other herbicides which have demonstrated effectiveness in nutsedge control may derive their potency from the preconditioning effects of their cytokinin activity combined with their phytotoxicity.

Effect of N6-BA, GA3, and Removal of Terminal Buds on Dwarf Shoot Development in Pinus ponderosa1

Abstract Five year old container grown plants of Pinus ponderosa when treated with N6-BA at 500 and 1000 ppm during 1972 showed an increase in the number of dwarf shoots with developed buds on long shoots while lower concentrations used in 1971 were ineffective. Foliar applications of GA3 made during 1971 and 1972 were found not to increase bud development. Foliar applications of N6-BA applied in the spring of 1972 were more effective than fall applications. Removal of terminal buds also increased bud development within the dwarf shoot while combinations of N6-BA with removal of terminal buds was the most effective treatment.

Fascicle Density and Needle Growth Responses of Red Pine to Water Supply Over Two Seasons

The ontogeny of terminal growth in red pine (Pinus resinosa Ait.) suggests that the growing season in Michigan be divided into three 2—month periods: April—May,June—July, and August—September. It is during the middle period that mitotic activity at the shoot apex initiates dwarf shoot primordia in the bud for the subsequent season's foliage; thus, preconditioning one year has a strong effect on next year's growth. Water was applied to or withheld from the soil under 23—year—old trees in various combinations of the 2—month periods over two growing seasons. All effects of drought were greatest on the terminal shoot of the main stem, diminishing on terminals of branches with distance from the apex, and disappearing at the base of the crown. Shoot extension was governed equally by conditions of the middle period of the previous year and of the early period of the current year. Each year fascicle density was regulated only by water conditions of the early period of the current year, regardless of preconditioning. Spacing of needles on shoots depended on elongation of the stem internodes between dwarf shoots, and was independent of the number of fascicles. Number of fascicles per shoot was governed only by conditions of June—July of the previous year, with drought during this period reducing the number of 30%. Length of needles was related to two factors: the number of fascicles produced per shoot and the water treatment of the period during which needles elongated. Thus when the water supply of the middle of the previous year was deficient, fewer but longer needles were produced currently; when water during the middle of the current year was deficient, needles were reduced in length by about 30%. It is concluded that the interaction of two seasons' water supply are usually compensative, rarely additive. The average net effect on foliage production is along—term, year—to—year stability in photosynthetic potential for red pine.

A NEW VOLTZIALEAN CONE BEARING SEEDS WITH EMBRYOS FROM THE PERMIAN OF TEXAS

Description of the new cone is based on a single specimen from the Lower Permian Leonard Series of west Texas. The cone is 2.0 cm in diam. It has numerous fertile dwarf shoots subtended by ovate nonbifurcate bracts arranged in a compact spiral around the axis. The dwarf shoots are free from their subtending bracts and equal them in length. Each dwarf shoot is dorsiventrally flattened and bears about 30 sterile scales each of which is ovate and has a single vascular strand. These sterile scales are in spiral sequence but are lacking on the medial adaxial side of the dwarf shoot. A single flattened erect ovule is attached at the base on the adaxial side of the dwarf shoot and equals it in length. Tracheids and elongate parenchyma cells enclosed by the megaspore wall of one seed give evidence of the oldest embryos on record. Their occurrence in seeds that remain in the cone indicates that the kind of development in most modern plants, in which embryo growth precedes seed dispersal, had evolved by Lower Permian time. Moyliostrobus texanum gen. et sp. n. combines features typical of the Lebachia and Ernestiodendron types of cones.

A Biometric Study of Leaf Variation in some British Birch Populations

Biometric methods for identifying and defining the European birch species, genus Betula L., by means of the characteristics of the leaves from vegetative dwarf shoots were first developed by Jentys-Szaferowa in Poland. This paper describes a modification of her method, made possible by the advent of the electronic computer, and its application to leaf samples of British birch. Two principal component analyses of nine variables have been carried out on material collected from thirty-two localities in Britain. The results support the classification adopted at present in British floras. They also indicate that it may be possible in future to identify both the species and geographical region of sample material.

Diffusible and Extractable Growth Regulators in Normal and Dwarf Shoot Apices of Peach, Prunus persica Batsch

Brian and Hemming (1), upon educing genetic dwarfs to behave as normal plants by applications of gibberellic acid, proposed that dwarfism was hormonally regulated. Phinney and his co-workers (12) expanded this idea by proposing that dwarfism in corn (Zea mays) is controlled by nonallelic genes, each of which governs a different step in gibberellin biosynthesis. They found that in this species the dwarf character, when transmitted as a recessive factor, can be altered by successive application of GA so that the seedling develops, flowers, and fruits as a normal plant. However, seedlings which inherit the dwarfing character as a dominant factor do not respond to GA treatments. Similarly, dwarf peas (Pisum sativum) respond to GA applications but the normal seedlings do not (2, 8). In rice (Oryza sativa), both the dwarf and semidwarf cultivars respond to exogenous GA. In contrast to the above species, applications of GA to normal peach (Prunus persica) seedlings accelerate shoot growth and inhibit flower bud formation (3), whilt the same treatments to dwarf progenies evoke a meager growth response. Moreover, the dwarf character in this species is transmitted as a simple recessive Mendelian factor; hence, it is likely determined by an allele and a single gene. It appears that while the genetic heritability of dwarfism in peach is simple, the mechanism controlling this character is dissimilar to that of other sp:cies mentioned above. To explore this dwarfing mechanism in peach, the levels of free diffusible and extractable gibberellin-like substances, IAA and ABA, in the shoot apices of dwarf and normal seedlings were compared.

The shoot apex in eastern white pine: its structure, seasonal development, and variation within the crown

Structure of the shoot apex in eastern white pine (Pinus strobus L.) was similar to that described for other members of the genus. The overwintering bud contained all primordia for the next season's growth, and the apical meristem exhibited ginkgoid cytological zonation. Seasonal development at the shoot apex was divided into three phases: dormancy, extension of overwintering bud accompanied by formation of new cataphylls, and formation of primordia in the axils of some cataphylls. Terminal shoot apices decreased in size and number of primordia with lower position in the crown. Height/diameter ratio of the apical meristem increased with lower crown position, and cytological zonation was absent in apices in the lowest part of the live crown. Such variation within individual trees makes it difficult to describe or compare species on the basis of limited sampling. By late summer or early fall of the present study, dwarf shoot primordia possessed sheath scale and needle primordia. But primordia of flower buds and lateral vegetative buds could not be distinguished from them. Past work with soft pines has shown similar results. Hard pines, on the other hand, have been shown to differentiate flower bud primordia during the season of their formation.

Developmental Patterns of Axillary Meristematic Activity in Seedlings of Pinus

Patterns of axillary meristematic activity were determined for nine species grown 120 days in a controlled environment with a 141/2-hr photoperiod and 20 C temperature. For species forming a terminal bud during the growth period, axillary meristematic activity generally declined to a low frequency in nodes 10-20 and thereafter increased rapidly to 100% frequency. Axillary meristems proximal to the cotyledons developed as lateral branches, while those proximal to the stem apex formed dwarf shoots. Substantial variation in the frequency of axillary meristems was noted for different species.

THE PATHOLOGY OF HYPODERMELLA LARICIS ON LARCH, LARIX OCCIDENTALS

A study of the larch needle disease caused by Hypodermella laricis provided information on the mode of infection, the manner of spread, and the relationship between the parasite and its host, Larix occidentalis. Infection by spores occurs in early spring as soon as the leaves emerge, but there is no evidence that hyphae invade the dwarf shoots. The fungus disrupts the normal abscission mechanism, and the fructifications and spores of H. laricis develop on the leaves which remain attached to the dwarf shoots. The time of precipitation is a decisive factor in the initiation of the disease, i.e., infection occurs only when precipitation coincides with the emergence of young leaves. However, vulnerability to infection diminishes rapidly as the leaves mature. By observing leaf size and noting the time of rainfall, the severity of infection can be accurately predicted. Several adaptive mechanisms related to successful parasitism in H. laricis are discussed.

Histogenese und morphologische Deutung der Doppelnadelnvon Sciadopitys

Summary The vegetation cone of the long shoots of Sciadopitys shows the zonation pattern characteristic for higher Gymnosperms with a tunicalike outer layer dividing periclinally in the apicalzone only occasionally (F oster’s apical initial group). Beneath this region larger cells are located with less dense cytoplasm (central mother cells) from which all cell rows of the vegetation cone originate. Below the central mother cells develops a cup-shaped zone of active cell divisions (cambi-forme meristem) which corresponds to the cambial-like zone of P opham and C han . Pith meristem and peripheral meristem arise from the central-mother-cell zone. The leaf formation is initiated by divisions of subepidermal cells of the vegetation cone. The leaf primordia develop apical initials which divide peri- and anticlinally according to the 2-cell-rhythm. Owing to a stronger development of the dorsal segments the leaf primordium hyponastically overarches the vegetation cone. Later on a subepidermal dorsal meristem originates on the dorsal side of the scale leaves. The double needles are formed as axillary shoots in the axils of the scale leaves predo-minantely by periclinal divisions of the subepidermal cells of the vegetation cone. In this way anticlinal cell rows are brought about. In more advanced stages the double needles show a similar zonation at their tips as the vegetation cones of the long shoots. The apex of the double needle is covered with a single layered tunica which does not divide periclinally. The formation of this tunica layer can be explained by the fact that the dermatogen of the long shoot apices is already developed as an individualized layer at the level of the axillary buds. Below the tunica there is a group of central mother cells in which all cell rows converge. A distinct initial group at the tip of the short shoots is missing; this lack may perhaps be interpreted by the early cessation of the apical growth of the double needles. The absence of the cambiforme meristem in the apex of the double needles can probably be deduced from the fact that practically no organ formation takes place. In the last stage of the apical growth of the double needles the cell division activity in the middle of the tip is strongly reduced while 2 protuberances are formed on both flanks by continous periclinal divisons of the first subepidermal layer. Thus, they owe their origin to a cambium-like meristem (arranged in cell rows) and are perhaps to be interpreted as rudimentary leaves. The apical growth of the short shoots is thereby stopped and replaced by a basal intercalary meristem. Also growth in width and thickness originates from a subepidermal meristem (arranged in cell rows) which consequently surrounds the whole primordium of the double needle. Marginal cells which are characteristically for the margin formation of leaves are not developed. Since the main part of the double needles is formed by elongation of the basal zone below the vegetation cone, a comparison of the double needles of Sciadopitys with2needles of a dwarf shoot of Pinus congenitally grown together seems to be questionable. Die Arbeit wurde von der Deutschen Forschungsgemeinschaft gefordert, wofur ich hiermit meinen Dank aussprechen mochte. Herrn Professor Dr. E. M. Gifford und Frau Professor Dr. K. Esau, University of California, Department of Botany, Davis/California, sowie Herrn Professor Dr. W. Rauh, Botanisches Institut der Universitat Heidelberg, bin ich fur wertvolle Ratschlage und Hinweise, die sie mir zuteil werden liesen, zu Dank verpflichtet. Herrn Dr R. Schindler, Botanisches Institut der Universitat Heidelberg, danke ich fur die Ausfuhrung der Zeichnungen in Tusche.

The Morphology of Normal, Callused, and Rooted Dwarf Shoots of Slash Pine

1. An investigation of callus and root formation in dwarf shoots of slash pine (Pinus elliottii Engelm.) reveals that cortex and pith contribute largely to callus formation but that cambial cells and xylem and phloem parenchyma are also capable of proliferation. 2. Roots originate from finger-like protuberances of the callus, but excessive callus formation impedes root development. 3. Buds develop from the apical meristem as early as 1 month after planting and in advance of root development. On rare occasions these buds succeed in forming new stems on rooted dwarf shoots. 4. Individual needles are capable of callus formation and root development.

Morphological and Ontogenetic Studies on Torreya californica. II. Development of the Megasporangiate Shoot Prior to Pollination

Kemp, Mahgaret. (Smith Coll., Northampton, Mass.) Morphological and ontogenetic studies on Torreya californica. II. Development of the megasporangiate shoot prior to pollination. Amer. Jour. Bot. 46(4): 249–261. Illus. 1959.—The development of the megasporangiate of Torreya californica during the first part of its maturation cycle of 26 months is described in detail. This first developmental period extends from the initiation stage in late July of one year through pollination of the young ovules in April of the following spring. At the end of this period, the reproductive shoot is a loosely organized, compound, determinate structure. It consists of a short primary axis which originated in the axil of one of the last formed bud scales or one of the first formed foliage leaves of the vegetative bud. This primary axis bears only 2 lateral and oppositely placed prophylls which stand at right angles to the subtending structure. In the axil of each prophyll is a short secondary axis which bears 2 successive pseudodecussate pairs of subopposite, sterile, scale-like perianth segments below a solitary, erect, terminal ovule. The integument of the ovule originates as a single lateral primordium, but its margins quickly merge and at pollination time it is a tubular envelope free from the nucellus. The nucellus, which is massive and contains a single deeply imbedded megasporocyte, terminates the secondary axis. Histogenetically, both primary and secondary axis systems of the megasporangiate shoot resemble a vegetative dwarf shoot. They both originate as axillary mounds of uniformly meristematic cells, whose apices soon exhibit a zonal pattern comparable to that of the apex of the vegetative shoot of the same species. The determinate nature of the primary axis is caused by cell senescence in its apex. The prophylls of the primary axis and the perianth segments of the secondary axes are comparable to bud scales of the vegetative bud in their arrangement, their origin from subsurface layers, the presence of apical and subapical initials which produce their first vertical growth, a basal intercalary meristem which completes their elongation, and marginal initials which produce a slender wing to the lamina of each type of cataphyll. At maturity all 3 types of cataphylls are basically similar in their histology. The apex of each secondary axis, at the initiation of the integument, shows an altered cellular pattern which rapidly becomes organized into a conspicuous fanshaped coaxial system as the central portion develops directly into the massive, cauline nucellus. This coaxial apical configuration differs markedly from the zonal pattern of the vegetative shoot apex and also from the similar zonal pattern in the apex of the primary axis of the megasporangiate shoot and its secondary axes during an earlier period of indeterminate growth.

MORPHOLOGICAL AND ONTOGENETIC STUDIES ON TORREYA CALIFORNICA. II. DEVELOPMENT OF THE MEGASPORANGIATE SHOOT PRIOR TO POLLINATION

Kemp, Mahgaret. (Smith Coll., Northampton, Mass.) Morphological and ontogenetic studies on Torreya californica. II. Development of the megasporangiate shoot prior to pollination. Amer. Jour. Bot. 46(4): 249–261. Illus. 1959.—The development of the megasporangiate of Torreya californica during the first part of its maturation cycle of 26 months is described in detail. This first developmental period extends from the initiation stage in late July of one year through pollination of the young ovules in April of the following spring. At the end of this period, the reproductive shoot is a loosely organized, compound, determinate structure. It consists of a short primary axis which originated in the axil of one of the last formed bud scales or one of the first formed foliage leaves of the vegetative bud. This primary axis bears only 2 lateral and oppositely placed prophylls which stand at right angles to the subtending structure. In the axil of each prophyll is a short secondary axis which bears 2 successive pseudodecussate pairs of subopposite, sterile, scale‐like perianth segments below a solitary, erect, terminal ovule. The integument of the ovule originates as a single lateral primordium, but its margins quickly merge and at pollination time it is a tubular envelope free from the nucellus. The nucellus, which is massive and contains a single deeply imbedded megasporocyte, terminates the secondary axis. Histogenetically, both primary and secondary axis systems of the megasporangiate shoot resemble a vegetative dwarf shoot. They both originate as axillary mounds of uniformly meristematic cells, whose apices soon exhibit a zonal pattern comparable to that of the apex of the vegetative shoot of the same species. The determinate nature of the primary axis is caused by cell senescence in its apex. The prophylls of the primary axis and the perianth segments of the secondary axes are comparable to bud scales of the vegetative bud in their arrangement, their origin from subsurface layers, the presence of apical and subapical initials which produce their first vertical growth, a basal intercalary meristem which completes their elongation, and marginal initials which produce a slender wing to the lamina of each type of cataphyll. At maturity all 3 types of cataphylls are basically similar in their histology. The apex of each secondary axis, at the initiation of the integument, shows an altered cellular pattern which rapidly becomes organized into a conspicuous fanshaped coaxial system as the central portion develops directly into the massive, cauline nucellus. This coaxial apical configuration differs markedly from the zonal pattern of the vegetative shoot apex and also from the similar zonal pattern in the apex of the primary axis of the megasporangiate shoot and its secondary axes during an earlier period of indeterminate growth.