Dwarf Shoots Research Articles

Some artificial genera (Fagaceae, Platanaceae, Araliaceae) of Upper Cretaceous of the Northern Hemisphere and heterophylly in some modern hybrids

Pedate or three- pieced leaves of Upper Cretaceous angiosperm genera of Europe and North America, Dewalquea, Araliophyllum, Araliopsis and Proteophyllum are investigated for their cuticles. Most of the European samples yielded only one epidermis type pointing to Fagaceae (Castanopsis Pasania), which is confirmed by fine venation. Some specimens of the Czech Cenomanian seem to have belonged to Araliaceae (Oreopanax). In addition, the leaf morphology in question is common in several remains of Platanaceae with comparable cuticles. In view of the phylogeny, Platanaceae and Fagaceae families are closely related. Heterophylly in Lianas and some modern hybrids of Ranunculaceae, Oleaceae and Fagaceae suggests that an apparent irregular leaf-growth predominated during Cretaceous resembling pteridosperms or ferns. In atavistic accelerated meristem grow that the leaf bases and the margins. It is concluded that long or dwarf shoot growth and timbers occurred during Cretaceous. It has been concluded that most of simple leaves of Tertiary and Present time must have been derived from the pedate type of Cretaceous.

In Vitro Responses of Tissues from Rhododendron Plants With and Without Tissue Proliferation

Rhododendron `Montego' shoot cultures initiated from plants with and without tissue proliferation (TP and NTP) served as explant sources for all studies (Note: in vitro TP shoot cultures produce primarily dwarf shoots, some long shoots, and stem tumors). Calli induced from TP leaves and tumors and NTP leaves were cultured on woody plant (WP) medium containing NAA and 2-iP. During the first 4 weeks of culture, calli from NTP leaves had higher relative growth rates than calli from TP leaves or tumors. However, calli from TP leaves and tumors grew faster than calli from NTP leaves for all subculture periods that followed. Shoot tips (5 mm) were excised from TP dwarf shoots, TP long shoots, and NTP shoots and were cultured on WP medium with or without 15 μM 2-iP. Shoot tips from TP dwarf and long shoots multiplied on medium without 2-iP, averaging 18.4 and 1.7 shoots per shoot tip in 12 weeks, respectively. Shoot tips from NTP shoots only multiplied when maintained on 2-iP-containing medium. When placed on 2-iP-containing medium, both types of TP shoot tips produced clusters of callus-like nodules that gave rise to highly tumorized, short shoots or leafy meristems.

Pinus Pollen Cones from the Middle Eocene Princeton Chert (Allenby Formation) of British Columbia, Canada

Anatomically preserved pollen cones are described from the Middle Eocene Princeton chert of British Columbia, Canada. Cones are ellipsoidal; range from 2.8 to 6.9 mm in length, 1.6 to 3.5 mm in diameter; and are often subtended by scale leaves. Cone axes contain longitudinally oriented, cortical resin canals and 14-18 vascular bundles. Microsporophylls are helically arranged, each bearing two abaxial pollen sacs, many containing pollen grains. Grains are bisaccate and monosulcate, ranging from 50 to 70 μm in length and 27 to 43 μm in width. Proximally, the corpus is rugulate with a tectate-alveolate infrastructure. Sacci have a well-defined endoreticulum and an external ornamentation that is psilate to scabrate. Variations in cone size, cone anatomy, and pollen morphology indicate that several developmental stages are preserved. The large number of cones present in the chert, especially those representing short-lived ontogenetic stages, and the preservational quality of the cones support depositional interpretations for a rapid burial and preservation. These factors also indicate that the pollen cone-producing plants occupied a marginal position in proximity to the lacustrine environment. Four species of Pinus, based on woody twigs, dwarf shoots, leaves, and ovulate cones, are presently known from the Princeton chert. The association of these pollen cones with Pinus similkameenensis leaves and Pinus arnoldii ovulate cones indicates possible taxonomic affinities among these species. The Princeton chert specimens are the oldest Pinus pollen cones to be described and are the first in the genus for which fossil pollen ultrastructure has been described.

Towards a Protocol for the Micropropagation ofPinus patula

SYNOPSIS In this investigation, different approaches to the micropropagation of P. patula were attempted and assessed in order to identify the most promising one for commercial application. Of the regenerative routes investigated, viz. axillary bud proliferation (dwarf shoot formation) from juvenile shoots, adventitious bud production and somatic embryogenesis from young seedlings, the first appears to have the most potential in terms of yield, time in culture and availability of explant material.

Comparison of growth and gibberellin concentrations in shoots from orchard‐grown standard and thermosensitive dwarf apple trees

Apple (Malus domestica Borkh.) trees were propagated by budding from selected fully grown hybrids that ranged in height from 1.5 to 8 m. The growth and development of the selected budded trees after 7 years in the orchard was similar to that of the parent trees. Additional grafting studies showed that the dwarfism was not associated with the roots. Differences in photosynthetic activity and associated processes were not related to the size difference between tissue culture‐propagated orchard‐grown standard cv. Golden Delicious and dwarf hybrid trees. Applications of GA3 did not stimulate elongation of shoots of dwarf trees. Shoots of both standard and dwarf trees started to develop in mid‐April when they contained nearly the same amounts of GA1, GA3 and GA8, but standard shoots contained higher concentrations of GA19, GA20 and GA29. On 2 June standard shoots were almost three times the length of dwarf shoots, but the number of leaves and area per leaf were nearly the same. The relative amounts of GAs on 12 May and 2 June for both plant types were similar to those on 20 April, except that GA19, GA20, GA1 and GA29 levels had declined. Gibberellin levels in standard shoots declined further between 2 and 22 June, after which there was no further shoot elongation or production of new leaves. Between 2 June and the end of the growing season, when summer temperatures were high, dwarf shoots continued to elongate slowly and to develop new leaves, which expanded little. During this time, the GA19 content of dwarf shoots nearly doubled, whereas the amounts of GA20, GA1, GA29 and GA8 declined. By the end of the season, standard shoots were 40 cm in length with 20 leaves and dwarf shoots were 28 cm in length, but with 36 leaves. High summer temperatures appear to induce loss of GA‐responsiveness in orchard‐grown dwarf trees and to cause a reduced rate of conversion of GA19 to GA20 in these genotypes.

SILICIFIED PINUS REMAINS FROM THE MIOCENE OF WASHINGTON

Silicified leaves, dwarf shoots, pollen cones, and seed cones of Pinus from a Late Miocene chert bed within the Yakima Basalt Formation near Yakima, Washington are interpreted as coming from a single new species, P. foisyi. The needles and dwarf shoots are those of a three‐needle pine. The needles contain two to four medial resin canals, a biform hypodermis, and endodermal cells with uniformly thickened walls. The pollen cones are ellipsoidal and about 1 cm long, and many contain bisaccate pollen grains. The seed cones are at least 6 cm long and are slightly asymmetrical. The cone axis has a broad sclerotic outer cortex, and the seed wing extends from a thick parenchymatous base. The scale apex bears a conspicuously swollen projection. The foliage and seed cones are identifiable with the Subgenus Pinus, Section Pinus, Subsection Oocarpae independently of one another, and together indicate a fossil species related to the modem Californian closed cone pines. Pinus foisyi represents one of the earliest occurrences of cone asymmetry associated with this group. However, cone serotiny characteristic of the modem species appears to have evolved after the Late Miocene.

Aggregated Cones in Pinus Halepensis

Aggregated female cones were found in 192 Pinus halepensis trees growing in 54 populations in Israel, in habitats of vastly differing ecological conditions. All of these trees also carried normal (1-5 in a whorl) female cones. The number of aggregates per tree varied from one to several dozen. Some of the trees formed aggregates every year, after the first year of aggregate formation, while others formed aggregates only once, or at long intervals. Not all cones in the aggregates reached maturity. The number of cones in an aggregate ranged from six to 62, and they were usually smaller than normal. Many of the trees with aggregates showed other abnormalities, e.g., individual female cone scales, proliferated dwarf shoots, three-needled dwarf shoots, shorter cone stalks, needles on cone stalks, larger terminal cones on the main axis in cones formed during the current year, proliferated female cones, and degradation of the main axis above the aggregate. The clusters probably result from replacement of dwarf shoots by ovulate cones.

Growth ofPinus radiatain relation to foliar element concentrations on ultramafic soil, New Zealand

Abstract Nine-year-old Pinus radiata in a plantation on uitramafic soil at Black Ridge, Southland, vary greatly in size. Four measures of growth (tree height, basal diameter, and dwarf shoot size and weight) were recorded in 50 plants, together with concentrations of 18 elements in current-year follage. Correlation coefficients and multiple regression of element concentrations against tree height Indicated that phosphorus, potassium, copper, and nitrogen were the main elements influencing Pinus radiata growth on this soil.

A new interpretation on the structure of Sahnia nipaniensis Mittre from the Rajmahal Hills

Description of five, serial, longitudinal sections cut through a male flower Sahnia nipaniensis of the Pentoxyleae, collected from the Rajmahal Hills, Bihar has been given. The flower was borne terminally on a dwarf shoot. Sporophylls are spirally arranged around a cylindrical receptacle. Sporangia are produced in opposite rows. Restoration of the flower is also given.

Long-shoot bud development, shoot growth, and foliage production in provenances of lodgepole pine

Long-shoot bud development, shoot growth, and foliage production were studied in seven provenances of Pinuscontorta Dougl. ssp. latifolia Engelm. from the major sites in British Columbia and one Yukon source growing in a provenance trial at Prince George, B.C. Branch terminal apical mitotic activity began in early March and continued until late September. Initiation of axillary buds began in May, about 2 weeks after the initiation of the subtending cataphyll. Differentiation of dwarf shoots began in early July to mid-August and continued until late October in some sources. Distal axillary buds had not always differentiated by late October in the southern sources. The duration of the period of apical growth and apical size during activity were related to final cataphyll numbers. Provenances with the widest, flattest, dormant apices produced the most cataphylls. The two northern provenances had more terminal sterile cataphylls but fewer sterile cataphylls lower in the long-shoot bud and shorter mean stem unit lengths than the others. Differences among provenances in shoot length were due mostly to variation in stem unit numbers. The large proportion of polycyclic long shoots in some provenances contributed to variation in dwarf shoot numbers.

Ent-Kaurene Biosynthesis in Cell-Free Extracts of Excised Parts of Tall and Dwarf Pea Seedlings

Investigations on the sites of ent-kaur-16-ene (ent-kaurene) biosynthesis were conducted with cell-free extracts from several excised parts of 10-, 13-, and 16-d-old tall and dwarf pea (Pisum sativum L.) seedlings. [(14)C]Mevalonic acid was incorporated into ent-kaurene in cell-free extracts from young developing leaves and elongating internodes of tall (;Alaska') and dwarf (;Progress No.9') pea seedlings at all three stages of development. ent-Kaurene biosynthesis also occurred readily in cell-free extracts from shoot tips, petioles, and stipules near the young elongating internodes. The ent-kaurene-synthesizing activity found in young developing tissues declined as tissues matured. Little or no activity was detectable in enzyme extracts from cotyledons and root tips at different stages. In light grown tall pea internodes ent-kaurene-synthesizing activity was low as they began to elongate, reached a maximum when the internodes reached about 2 cm in length and declined as they matured. Activity in extracts of dwarf shoot tips and internodes was generally lower than in equivalent tall plants, but the activity in dwarf leaves and stipules was somewhat higher than in tall plants. With the exception of root tips, there is a strong correlation between growth potential of a tissue and the rate of ent-kaurene biosynthesis in extracts from that tissue.

The Fate of the Dwarf Shoot Apex in Bristlecone Pine (Pinus longaeva)

The fate of the pine dwarf shoot (DS) apex after needle initiation has been controversial. Dwarf shoot primordia of Pinus longaeva were examined to determine the developmental basis for DS with and without interfoliar buds. Interfoliar buds are microscopic buds derived from the original terminal apex of the DS. In October, all the DS primordia are similar in size and appearance. However, as the needles elongate in the following June the apices of more proximal DS decrease in size, such that by July there is a clear diminishing size gradient of apical domes in going from the most distal to the most proximal positions. The distal DSs start to form bud scales in July and have fully formed interfoliar buds by mid-August. In contrast, those DS apices lacking protective bud scales at needle maturity become suberized and can never proliferate into long shoots. The distal placement of interfoliar buds may be due to a group effect, where each developing DS inhibits the more proximal DSs in the long shoot terminal bud.

THE FATE OF THE DWARF SHOOT APEX IN BRISTLECONE PINE (PINUS LONGAEVA)

The fate of the pine dwarf shoot (DS) apex after needle initiation has been controversial. Dwarf shoot primordia of Pinus longaeva were examined to determine the developmental basis for DS with and without interfoliar buds. Interfoliar buds are microscopic buds derived from the original terminal apex of the DS. In October, all the DS primordia are similar in size and appearance. However, as the needles elongate in the following June the apices of more proximal DS decrease in size, such that by July there is a clear diminishing size gradient of apical domes in going from the most distal to the most proximal positions. The distal DSs start to form bud scales in July and have fully formed interfoliar buds by mid‐August. In contrast, those DS apices lacking protective bud scales at needle maturity become suberized and can never proliferate into long shoots. The distal placement of interfoliar buds may be due to a group effect, where each developing DS inhibits the more proximal DSs in the long shoot terminal bud.

Bacterial Canker of Sweet Cherry (Prunus avium) in Poland

AbstractIn Polish climatic conditions cherry cankers resulting from infection by Pseudomonas morsprunorum continue development in summer, but the rate may be slower than in the period from April to June.However, from the well established, active canker developing under the dwarf shoot of the susceptible variety‘Hedelfińska’in July no P. morsprunorum were isolated. On the other hand, numerous strains of the genus Erwinia were found there which caused a hyper sensitivity reaction (HR) on tobacco leaves. From the cracks on the current‐year cherry shoots, due to fresh infection and from symptomless leaves P. morsprunorum strains were isolated, always accompanied by those of the Erwinia genus in the approximate proportion 1: 1 or 1:2.The strains of Erwinia genus seemed similar to the DC and YC strains isolated by BILLING and BAKER from pear and apple trees infected by fireblight and also to the strains in group III of the bacteria isolated by CROSSE from cherry leaves.In two tests (immediately after isolation and after 4 months of storage) the strains of the Erwinia genus and 3 nonidentified isolates induced HR. At a third test, after 10 months of preservation these strains were HR‐negative in contrast to the P. morsprunorum isolates.The fact that strains of the Erwinia genus inducing HR were isolated in large numbers from active cherry canker where pathogenic bacteria were not detected, may indicate that they play some role in the development of cherry tree canker.

The determinate and indeterminate dwarf shoots of Pinus longaeva (bristlecone pine)

The dwarf shoot of the genus Pinus is normally regarded as a determinate short shoot, but the fate of the dwarf shoot apex after needle maturity and the origin of proliferated dwarf shoots remain controversial. To resolve these issues, 1- to 28-year-old dwarf shoots of P. longaeva were microscopically examined and experimentally manipulated. Eighty-eight percent of the lateral long shoots and all trunks had "proliferated dwarf shoots," or dwarf shoots that had become long shoots. On trunks 44.3% of the dwarf shoots had terminal buds, versus 6.6% on lateral long shoots. Most of these buds were microscopic, "interfoliar buds," derived from the original dwarf shoot apex. With advancing age of dwarf shoots there was no statistically significant change in the percentage of dwarf shoots with buds. The fate of the dwarf shoot apex depends upon the position of the dwarf shoot within its age-class and the type of long shoot. On lateral long shoots, only distal dwarf shoots have interfoliar buds and only these may spontaneously proliferate or be experimentally induced to proliferate into long shoots. Proximal dwarf shoots have a suberized apex. On trunks, both distal and proximal dwarf shoots often have buds and can thus proliferate. Dwarf shoot proliferations therefore arise predictably from interfoliar buds and not adventitiously.

RESOURCE ALLOCATION ON DWARF SHOOTS OF BIRCH (BETULA PENDULA): REPRODUCTION AND LEAF GROWTH

SUMMARYA hypothesis that the female catkin and leaves on the same dwarf shoot of birch compete for the same limited resources of the bud during their development has been tested with Betula pendula. In all trees studied the mean length of leaves, both in May and July, was 15 to 20% lower on reproductive dwarf shoots with a female catkin than on non‐reproductive dwarf shoots of the same tree. However, there were no significant differences in leaf number or in bud development. The idea of plants as metapopulations and the cost of reproduction in trees are discussed.

Longevity of needle fascicles of Pinus longaeva (Bristlecone pine) and other North American pines.

Variation in leaf longevity of gymnosperms has received surprisingly little attention despite its likely adaptive significance. Pinus longaeva, a pine of arid, subalpine environments in the western United States, has the record among conifers for needle longevity, with a maximum dwarf shoot (needle fascicle) retention time of up to about 45 years. Most low elevation pines have dwarf shoot retention times (DSRs) of two to four years. Literature data for the 37 species of Pinus native to the United States and Canada and field data for eight taxa (21 populations) of pines growing at various elevations in California each show a strong positive correlation between elevation and DSR, respectively, r=+0.65, df=35, p<0.001 and r=+0.82; df=19, p<0.001. We propose that extended needle fascicle longevity represents an adaptation to arid and especially high elevation environments. Field data from native stands and common gardens indicate that differences between taxa in DSR relate to both genetic and environmental factors. When grown at the same sites certain species (eg, P. longaeva, P. monophylla) had much longer DSRs than others, indicating a genetic basis for differences in needle fascicle longevity. For six of seven taxa that were each studied at more than one elevation there was a statistically significant increase in DSR in going from the lowest to the highest elevation site, indicating strong environmental control of needle fascicle longevity.The physiological control of dwarf shoot senescence and abscission is poorly understood. For P. longaeva dwarf shoots of a particular age class are not shed simultaneously; rather there is a more or less gradual attrition of dwarf shoots from the long shoot. Although different types of long shoots of pines are known to differ physiologically, for P. longaeva there was no consistent difference in DSR on various types of lateral long shoots (eg, vegetative, pollen cone-bearing, seed cone-bearing), nor was there a statistically significant difference in DSR on trunks versus on their lateral long shoots. In addition, for P. contorta ssp. bolanderi and P. muricata needle fascicle longevity was not affected by the degree of edaphically induced dwarfing (ie, stunting) of the trees.

MORE EVIDENCE FOR CONIFER DIVERSITY IN THE UPPER TRIASSIC OF NORTH CAROLINA

An ovulate strobilus from the Upper Triassic Deep River Basin, North Carolina, has helically arranged, loosely aggregated, elongated, spatulate bracts with axillary ovule‐bearing appendages with about 8–10 ovules attached in two lateral rows, with outwardly directed micropyles. The axillary ovuliferous appendage is homologous with the voltzialean fertile dwarf shoot, but probably not directly evolved from it. More credible is a suggested origin from a completely fertile axillary appendage such as that of the Lower Permian Trichopitys. The occurrence of this cone, Metridiostrobus palissyaeoides, gen. and sp. nov., along with Compsostrobus neotericus and Voltzia andrewsii, reflects considerable diversity among conifer ovulate cones during the Upper Triassic.

More Evidence for Conifer Diversity in the Upper Triassic of North Carolina

An ovulate strobilus from the Upper Triassic Deep River Basin, North Carolina, has helically arranged, loosely aggregated, elongated, spatulate bracts with axillary ovule-bearing appendages with about 8–10 ovules attached in two lateral rows, with outwardly directed micropyles. The axillary ovuliferous appendage is homologous with the voltzialean fertile dwarf shoot, but probably not directly evolved from it. More credible is a suggested origin from a completely fertile axillary appendage such as that of the Lower Permian Trichopitys. The occurrence of this cone, Metridiostrobus palissyaeoides, gen. and sp. nov., along with Compsostrobus neotericus and Voltzia andrewsii, reflects considerable diversity among conifer ovulate cones during the Upper Triassic.

Isolation of a dwarf plant responsive to exogenous GA3 from anther cultures of birdsfoot trefoil

A dwarf plant isolated from anther culture of a normal genotype of birdsfoot trefoil (Lotus corniculatus L. cv. Leo) has been isolated, characterized, and maintained as an in vitro shoot-tip culture. The dwarf condition is the result of a much shorter internode length when compared with a normal genotype in shoot tip culture. Dwarf shoots which are typically rosette respond to increased GA3 levels by increased internode growth. Normal genotypes are inhibited and eventually die as a result of increased levels of GA3 in the culture medium. This dwarf has the normal tetraploid chromosome number of 24, and although stable in shoot tip cultures since 1977, has not survived outside of in vitro shoot tip cultures.