Secondary Buds Research Articles

Epidemiology of Botrytis cinerea in Sweet Basil and Implications for Disease Management.

Sweet basil (Ocimum basilicum) is a herbaceous annual plant that is highly susceptible to gray mold, caused by Botrytis cinerea. Infections are initiated on the surface of stem wounds that are caused during harvest; the pathogen then progresses on the stem, killing leaves and secondary buds. When the infection reaches the main stem, the entire plant dies. A study of the epidemiology of the disease and of host-pathogen interactions led to the development of rules for effective disease management. The research was conducted in three steps. (i) Natural epidemics in commercial crops were monitored during the 1993 to 1994 and 1994 to 1995 growing seasons. Disease outbreaks were found to coincide with harvests during rainy days, whereas disease intensity did not change much when harvests were completed during rainless days. (ii) Studies under controlled environmental conditions revealed that cut ends of stems were highly susceptible soon after harvest, susceptibility diminished gradually, and stem cuts inoculated 48 h after harvest were rarely diseased. Observations under a scanning electron microscope showed that an opaque layer had appeared over the cut surface and, as the entire wound surface became covered, penetration of the fungus into the tissue was prevented. Based on these findings, it was hypothesized that avoidance of harvesting during rain events and application of one fungicidal spray, soon after harvest, would result in adequate disease suppression. (iii) These hypotheses were tested and corroborated in greenhouses in two experiments, in 1994 to 1995 and 1995 to 1996. Management of basil crops according to these concepts would also lower the risks for contamination of the marketable product with pesticide residues.

Ontogeny of proventitious epicormic buds in Quercus petraea. I. In the 5 years following initiation

The persistence of large epicormic shoots is one of the main factors that reduces timber quality and value in Quercus petraea. The early phases of epicormic shoot formation, i.e. the initiation of the epicormic buds, their survival and their proliferation over the years, are not clearly understood. In the present work, we studied the initiation of the axillary buds giving rise to epicormic buds and shoots, and followed their behaviour during the first 5 years using both scanning electron microscopy and light microscopy. Two types of proventitious epicormic buds have been identified. The first type has small axillary buds associated with the rings of bud-scale scars which are found at the base and tip of each growth unit. These buds are made of a terminal meristem surrounded only by scales; no leaf primordium is detected. During the second and third years of epicormic life, meristematic areas appear in the scale axil. Progressively, the meristematic areas organize into secondary bud primordia composed solely of the terminal meristem surrounded by scales. The second type of epicormic bud has secondary buds produced by a large axillary bud when this large bud either developed into a shoot or partially abscised. The epicormic potential in Q. petraea is characterized by a balance between the epicormic buds in apparent rest, enclosing meristematic areas and secondary bud primordia, and their mortality over the years.

Basipetal Gradient of Axillary Bud Inhibition Along a Rose (Rosa hybridaL.) Stem: Growth Potential of Primary Buds and their Two Most Basal Secondary Buds as Affected by Position and Age

Abstract In Rosa hybrida L. cv. Ruidriko ‘Vivaldi’®, the effect of position on growth and development potentials of axillary buds was investigated by single internode cuttings excised along the floral stem and its bearing shoot. The experiments were carried out in both glasshouses and in a phytotron. The study firstly concerned the development of the primary shoot from the onset of bud growth until anthesis. The primary shoot was then bent horizontally to promote the growth of the two most proximal secondary buds, the collateral buds, already differentiated inside the primary bud. They gave rise to basal shoots. In the basipetal direction, the axillary buds along the floral stem exhibited both an increase in the lag time before bud growth and a decrease in bud growth percentage, demonstrating the existence of a physiological basipetal gradient of inhibition intrinsic to the buds or due to short range correlations. The same basipetal gradient of inhibition was observed along the floral stem and its bearing shoot, demonstrating that the age of the bud was not a major factor in determining the rate of bud growth. After bending the primary shoot, the percentage of collateral bud growth was also affected by the cutting position. The more proximal the cutting, the lower the sprouting ability of collateral buds. The growth potential of these buds appeared to be already determined inside the main bud before cutting excision.

Polyaxial development in homeotic flowers of three begonia cultivars

Development of staminate flowers in double-flowering Begonia semperflorens-cultorum cultivars 'Cinderella', 'Goldie Locks', and 'Lucy Lockett' was examined using epi-illumination microscopy, focussing on later stages when secondary partial floral buds formed on the floral apex. This process, switching from floral to inflorescence-like development, is an example of homeosis, the expression of inflorescence features on a floral apex. Floral development began as in a normal begonia flower with the formation of a perianth consisting of two sepals and two petals, but sepaloid and (or) petaloid appendages then developed in what corresponded to stamen positions in normal Begonia species. This was usually followed by lateral elongation, distortion of the primary floral apex, and formation of secondary partial floral buds. The pattern of primordial inception on the secondary apices tended to be irregular, but in some cases, appendage primordia formed in groups of twos, threes, and fours, and in a somewhat alternating formation on the apices. Often, primordial initiation seemed to continue on secondary apices even after anthesis of the staminate flower. Appendage primordia that formed on the secondary buds usually were laterally elongate and bifacial, giving them a phyllomic appearance. Others were, on occasion, more hemispherical at inception, but as they developed they became phyllomic. Key words: homeosis, polyaxial, floral development, intermediate inflorescence.

Basal-shoot formation in young rose plants: Effects of bending practices and plant density

SummaryTo examine the relations between plant architecture and flower production, the effect of bending practices and plant densities on basal-shoot formation was studied in young rose plants. After bending the primary shoot, there was a greater probability for the outgrowth of the two most basal buds. These two buds are already present as secondary buds in the axils of the scales of the axillary bud when used as a cutting for propagation. This probability was even more apparent when bending was delayed. The source capacity of the primary shoot, mainly reflected in the leaf area index (LAI), was determined by date of bending. Delayed bending increased the development rate, diameter, weight and cross sectional area (CSA) of basal shoots per plant. Plant growth rate, expressed as dry-weight increment per day, was positively related with LAI (and thus light interception) during the early phase of basal-shoot formation, although a maximum in plant growth rate was reached when stems were bent 28 d after T0 (ti...

Microspore Culture of Winter Oil Rapeseed (Brassica Napus): II. Embryo Conversion, Plant Regeneration and Double Haploid Production of Brassica Napus L.

ABSTRACTSomatic embryos obtained via microspore culture of Brassica napus have been used for study plant regeneration and double haploid production. Two mode of plant regeneration were observed: direct embryo germination and secondary adventitious buds formation. Different number of plants have been obtained for studied genotypes. Improved direct embryo development was achieved when ABA in concentration 10 μmol for 14 days at 15°C was applied. Plants were successfully colchicine treated in in vitro rooting stage by double layer media. Colchicine solution in 0.1% concentration added as a second layer for 24 hours was optimal for double haploid production and did not suppress significantly plant development. Colchicine treatment of pot plants by cuttings or roots delay 3–4 months seeds harvesting. Sufficient number of double haploid plants for breeding purposes have been obtained.

Leaf initiation and de novo pattern formation in the absence of an apical meristem and pre-existing patterned leaves in watercress (Nasturtium officinale) axillary explants

The production of new buds was followed in five explants from leaf axils of watercress (Nasturtium officinale R. Br.). Watercress axillary tissue normally gives rise to a primary axillary bud and numerous roots which arise from conical organ primordia adaxial to the bud. The primary bud was excised from the explants but roots and organ primordia were left intact. A new secondary bud frequently formed within several days at a predictable position on the explant. In three cases, a set of approximately spirally arranged new leaf primordia formed in a roughly triangular region bounded by the cut edge of the explant and by a pair of existing organ primordia. Where there was variation in the shape of the triangular space, there was a corresponding variation in the pattern of leaves. Leaves formed in a closely packed cluster, but leaves originally in a single group could become recruited for different secondary buds. The first two to three leaves of a bud usually formed before an apical meristem dome was visible, but the dome could also be the first structure formed for the new bud. Prior to the appearance of the first sign of bulging for a new leaf primordium, cells at the leaf site divided and grew in a new orientation. The pattern of new leaf positioning is interpreted as arising from spatial constraints imposed by existing boundary structures and the newly formed primordia. Keywords: apical meristem, axillary buds, bud initiation, cytokinin, division orientation, leaf initiation, sequential scanning electron microscopy, phyllotaxis, watercress.

Benzylaminopurine induces phenocopies of floral meristem and organ identity mutants in wild-typeArabidopsis plants

Arabidopsis thaliana (L.) Heynh. has been used as a model system to investigate the regulatory genes that control and coordinate the determination, differentiation and morphogenesis of the floral meristem and floral organs. We show here that benzylaminopurine (BAP), a cytokinin, influences flower development in Arabidopsis and induces partial phenocopies of known floral homeotic mutants. Application of BAP to wild-type inflorescences at three developmental stages results in: (i) increase in floral organ number; (ii) formation of abnormal floral organs and (iii) induction of secondary floral buds in the axils of sepals. These abnormalities resemble the phenotypes of mutants, clv1 (increase in organ number), ap1, ap2, ap3 (abnormal floral organs) and ap1 (secondary floral buds in the axils of first-whorl organs). In addition, BAP induces secondary floral buds in the axils of perianth members of ap2-6, ap3-1 and ag mutants, and accentuates the phenotype of the ap2-1 mutant to resemble the ap2-6 mutant. These observations suggest that exogenous BAP suppresses the normal functioning of the genes for floral meristem identity and thereby affects flower development and the later stages of floral organ differentiation.

PENGARUH JENIS SETEK DAN MEDIA PEMBIBITAN TERHADAP PERTUMBUHAN BIBIT TANAMAN LADA (Piper nigrum L.)

The experiment was carried out at green house of Medicinal and Spice Plant Research Agency, Bogor from May to October 1993. The split plot design in randomized block design was applied for 2 factors and 3 replication. The main plot was 2 kind of bud (secondary branch bud and tertiary branch bud), and the sub plot was 5 different growth media consisted of sand + cow dung + top soil mixed i.e. 1 : 1 : 0 : 1 : 1 : 1 : 1 : 1 : 2 : 1 : 1 : 3 and 1 : 1 4.The kind of bud did not significantly influence the pepper seedling growth. The best seedling shoot growth was obtained by the combination treatments of sand + cow dung + top soil (1 : 1 : 0), and the best seedling root growth was obtained by the combination of sand + cow dung + top soil (1 : 1 : 2

Adaptive significance of sprouting ofEuptelea polyandra, a deciduous tree growing on steep slopes with shallow soil

We investigated growth characteristics ofEuptelea polyandra Sieb. et Zucc. (Eupteleaceae), a Japanese endemic deciduous tree species growing on unstable ground such as that of very steep slopes with thin soil.Euptelea polyandra began to sprout at the juvenile stage and had a multiple-stemmed tree form. There was a positive correlation between diameter of the maximumsized stem within a stool (DMS) and the number of stems within the stool. Many stools had suffered from disturbances as shown by the fact that uprooting scars were found on 31.4% and 42.4%, respectively, of the stools of the two populations studied. Sprouting played a significance role in repairing damaged stems and stools, and at least 15.5% and 18.2% of the stools of the two populations, respectively, had apparently avoided death by sprouting. Sprouted stems gradually inclined with the increase in their relative sizes within each stool, and this seemed to facilitate the establishment of younger sprouted stems. The small younger sprouted stems had their own roots. There were dormant buds on stems which originated from axillary buds, and secondary dormant buds occurred by branching. The total number of dormant buds in a stool increased with DMS. It is concluded thatE. polyandra accumulates dormant buds for sprouting in order to respond to disturbances quickly.

Rapid propagation through shoot tip culture of Trichopus zeylanicus Gaertn., a rare ethnomedicinal plant

Rapid micropropagation of Trichopus zeylanicus Gaertn. subsp. travancoricus Burkil ex Narayanan, a rare ethnomedicinal herb endemic to the Western Ghats of southern India, was achieved by culturing shoot tips (0.3-0.5 cm) of 2-month-old axenic seedlings on Woody Plant Medium. Among the cytokinins tested, only BAP induced callus-free multiple shoot bud formation, with a maximum of 8.5±0.4 buds per explant being obtained with 2.0 mg.l(-1) BAP after 8 weeks of culture. Shoot tips containing proliferated buds were divided and subcultured on medium containing 0.2 mg.l(-1) BAP to produce 12.0±1.0 shoots per explant in 6 weeks. Excision of buds after culture initiation, with subculture of the debudded basal tissue in 2 successive passages yielded 20.0±1.0 and 13.5±0.5 buds per explant respectively. Each bud cultured in turn for 4 weeks on WPM with 1.0 mg.l(-1) BAP formed 3.8±0.4 secondary buds which were repeatedly recultured to increase bud production. Altogether this method enabled an estimated harvest of 7848 buds from a single shoot tip in 28 months. Shoots (3-5 cm) developed from bud cultures were rooted in half-strength WPM medium with 0.5 mg.l(-1) each of NAA and IBA, and 90-100% of the rooted plants were established in the field after hardening. Micropropagated plants were grown to maturity free of defects in growth, morphological, flowering and seed set characteristics.

Relationship of Winter Stage of `Concord' Grapevine Buds, Previous Season, and Return Bloom

Overwintering buds and internodes of Vitis labruscana `Concord' were taken from minimal- (MP) and balance-pruned (BP) vines in Dec. 1993 and Dec. 1994 from canes whose weight, crop weight, total nodes, and nodes with periderm were known. Winter characters recorded were: node-5's primary bud basal area, total nodes, and developmental stage of cluster primordia; stage of largest cluster in the secondary bud; vascular area of cane internode 5. Fifty node-5 buds were tagged in each treatment and flower and fruit number per cluster later recorded. Regression analysis showed no effect of a shoot's crop, cane weight, node number, or nodes having periderm on any character measured in the overwintering buds or canes for either treatment. Regression analysis did show mean flower number per cluster was linearly related to mean winter stage per cluster in both treatments, with all values falling on one line. Differences between treatments were one of degree of cluster development; BP vines had more-developed winter and spring clusters and more flowers and fruit per shoot. The slope of the regression was identical the last 3 years, although the y intercept varied each year; thus, a given cluster stage in the overwintering bud was capable of producing a variable number of flowers the next season, depending on year. Flower number per shoot appeared positively related to growing-degree-days the previous season.

Thermotolerance of Dormant and Actively Growing Cabernet Sauvignon Is Improved by Heat Shock

Actively growing Cabernet Sauvignon plants grown at 25°C were given a four-hour heat shock at 40°C, followed by a four-hour incubation period at 25°C. The heat shocked plants, when compared to non-heat shocked plants, had less leaf damage, tissue water loss, and electrolyte leakage after exposure to 50°C. Dormant Cabernet Sauvignon cuttings were removed from 3°C cold storage and heat shocked for 30 minutes at either 45°C or room temperature (23°C). This was followed by a four-hour incubation period at room temperature. A group of non-heat shocked control cuttings were held continuously at 3°C. Thermotolerance was tested by placing the cuttings in water baths at 54°C, 56°C, 58°C, or 60°C for 30 minutes. Primary, secondary and tertiary bud survival, time required for buds to begin growth, and root vigor were evaluated for each treatment. Bud survival was high in all treatments at 54°C and 56°C, while at 60°C there was 100% bud mortality in all treatments. At 58°C, however, cuttings that were heat shocked at room temperature were significantly (<i>p</i> &lt; 0.01) more thermotolerant than the control cuttings, and those that were heat shocked at 45°C were significantly (<i>p</i> = 0.01) more heat tolerant than those heat shocked at room temperature. These results show that both dormant and actively growing grape tissues respond to heat shock treatment by increasing their thermotolerance. To our knowledge, this is the first time that heat shock responses have been shown to occur in dormant woody plant tissue. Heat shock treatment could lead to more effective pathogen elimination by allowing grape propagation material to be treated at higher temperatures than are currently possible.

Cold Hardiness of Dormant Buds of Grape Cultivars: Comparison of Thermal Analysis and Field Survival

Thermal analysis (TA) was used to evaluate dormant bud cold hardiness of nine Vitis cultivars weekly during the 1993–94 dormant period. TA hardiness estimates were expressed as either mean low-temperature exotherm temperature (MLTE) or temperatures lethal to 10% (LT10), 50% (LT50), or 90% (LT90) of dormant bud sample. A destructive freeze on 19 Jan. 1994 presented an opportunity to compare dormant bud field survival with laboratory estimates of bud hardiness that had been derived from TA. Vineyard air temperatures of –24C caused primary bud kill that ranged from a mean of 15% with `Concord' to 100% with `Viognier'. With the exception of `Viognier' and one of two `Cabernet Sauvignon' clones, field mortality levels were accurately bracketed by TA estimates of LT10, MLTE, and LT90 values, which had been obtained in the week preceding the freeze. `Viognier' bud hardiness was overestimated by ≈1.5C, and the hardiness of `Cabernet Sauvignon clone UCD#6' was underestimated by &lt;1C. The discrepancy with `Viognier' may have been related to prior destruction of primary buds by bud necrosis and the misinterpretation of secondary bud exotherms as due to primary buds.

094 CROPLOAD EFFECT ON BUD COLD HARDINESS OF Vitis labruscana L. cv. CONCORD

An increase in mechanical pruning of Concord grapevines in Washington has led to a marked increase in yield. In 1993 the average yield for the 20,000 plus acres was slightly greater than 12 ton/acre. As part of a long term study, initiated in 1987, to evaluate the effects of mechanical pruning on Concord yield and fruit quality, we have also followed bud cold hardiness and winter injury over several years. Cold hardiness was monitored using low temperature exotherm analysis of excised buds. Winter injury was evaluated by visual examination of bud and cane tissues collected from vines with different croploads. In 1990 the average yield for mechanically pruned vines was 13T/ac and for balance pruned vines about 8T/ac. Winter injury during December 1990 showed significantly less injury to mechanically pruned vines whether primary, secondary or tertiary buds were examined. During the winter of 1991-92 and 1993-94 bud cold hardiness of individual vines showed no relationship to cropload per vine.

396 CALLA LILY VEGETATIVE &amp; REPRODUCTIVE DEVELOPMENT PATTERNS

The release of latent buds (adaptive reiteration) and aerial shoot architecture of the rhizomatous calla lily plant has been researched for pot production. Rhizome mapping has explicitly shown vegetative and floral bud positioning in relation to tissue growth and expansion. Floral initiation normally occurred only on the mother portion of rhizomes. Gibberellic acid (GA3) application enhanced this phenomenon and caused initiation on daughter ramets. Bud excision performed at planting through Day 16 microscopically revealed lack of floral initiation in dissected meristems prior to planting, transition by Day 4, elongation beginning at Day 8 and `small to medium sized spadixes present by Day 12 and 16. Floral development was similar in treated and untreated primary buds, but delayed in secondary and tertiary buds with elongation occurring by Day 16. Pretreatment of GA3 prior to planting revealed spadix presence at Day 0. Floral development correlated with ramet size showed most flowers on largest ramets but formation on all sizes with GA3 treatment. GA3 also caused increased vegetative bud formation on rhizomes.

919 PB 197 YIELD ANALYSIS IN EASTERN THORNLESS BLACKBERRY

Easter thornless blackberries (ETB) are highly productive and commercially grow” in several areas of the country. Fruit are acceptable for the fresh market and the processor. Mature plants of ETB cultivars develop 3 or 4 primocanes annually. On these primocanes as many as 15 lateral shoots may develop from axillary buds. In 1992, the effects of lateral shoot numbers on axillary bud break, fruit cluster numbers, berry size, and yield were determined. `Black Satin' (9-yr-old) vines were dormant pruned to three floricanes with 3, 6, 9, or 12 l2-node lateral shoots (108. 216, 324, or 432 axillary buds per plant). In all plants, about 77% of primary axillary buds broke and grew into fruiting laterals. However, percentage bud break of secondary axillary buds was reduced as the lateral shoots per floricane increased. Pruning severity affected neither berry size (6.4 gm) or SSC (9.5%). Yield per lateral shoot was reduced as lateral shoot number increased. For higher fruit production in ETB, the number of primocanes as well as the lateral shoot numbers per plant must increase.

Cell-Layer Interactions Influence the Number and Position of Lateral Shoot Meristems in Nicotiana

In higher plants the formation of lateral shoot meristems (i.e., axillary meristems) in the axils of leaves establishes potential growth centers along the principal axis of the stem. The position and number of lateral buds in Nicotiana glauca , two genotypes of Nicotiana tabacum, and a series of interspecific periclinal chimeras composed of these species was studied to establish the role of position (location of the node along the main axis), flowering, and cell-layer interactions on the pattern of lateral meristem initiation. In N. glauca, both the number of nodes generated and the transition to flowering influenced the number and position of lateral meristems. A short-day mutant of N. tabacum grown under long days remained vegetative and never produced multiple lateral buds per node, indicating that attaining a certain node number was not sufficient to cause the formation of multiple buds. Yet, flowering plants of both short-day and day-neutral N. tabacum possessed multiple buds in their upper nodes. An analysis of the number of buds per node and bud position along the main axis in periclinal chimeras indicated that the genotype of the third apical layer (LIII) of the meristem had the greatest influence on the pattern of lateral shoot meristems in both vegetative and flowering plants. The lineage of the three apical layers (LI, LII, and LIII) of the terminal shoot meristem was preserved in primary (1°) lateral meristems but minor deviations in lineage were observed in secondary (2°) buds (i.e., those formed later but in the same node as the 1° bud). An analysis of the phenotype of 2° shoots that displayed deviations from expected lineage indicated that in most cases the periclinal cell divisions that destabilized the lineage occurred at the flanks of the meristem and began before the most basal node, indicating that periclinal cell divisions most likely occurred prior to the inception of the 2° lateral meristem. Based on our studies, we conclude that both 1° and 2° lateral meristems in Nicotiana ultimately descend from derivatives of all three apical layers of the terminal shoot meristem.

Ontogeny of axillary buds and shoots in roses: Leaf initiation and pith development

The ontogeny of an axillary bud (in the middle region of a shoot) from initiation up to flowering of the subsequent shoot was studied. The first secondary buds appeared in the axillary bud (primary bud) when the leaf subtending the primary bud unfolded. By that time, the primary bud contained seven leaves, including leaf primordia. During the development of the parent shoot to the harvestable stage, the number of leaves and secondary buds in the primary bud increased to 11 and four, respectively. The primary bud appeared to contain the lower part of the future shoot. After release from correlative inhibition, all the leaves and a flower bud had been formed within 10 days. No internodal elongation occurred between the scale-like leaves. Pith diameter was found to be correlated with the shoot diameter and was about 50% of the diameter of harvestable shoots. In the primary bud the cells of the pith were isodiametric and equal in size; they were vital and contained starch and sugars. Two weeks after release of the bud, the final pith diameter was reached at the base of the shoot. Two types of cells had differentiated: small, vital cells and large, dead cells. The small cells, which appeared to form a network throughout the pith, could contain starch and sugars, the large cells were filled with air. The number of cells on a diameter line of the pith was constant after bud break and slightly decreased from the base towards the top of the shoot.

Morphological study of the formation and development of basal shoots in roses

Basal shoots are the vigorous shoots at the base of the plant. In roses, basal shoots determine the potential flower production of the plant. Although many attempts have been made to promote the formation of basal shoots for commercial production, little attention has been paid to the origin and development of these shoots. The present study addresses this by following the development of a rose plant, raised from a cutting. Basal shoots only originated from basal axillary buds and not from adventitious buds. The first basal shoot of a plant emerged from one of the two most basal axillary buds of the primary shoot. The second basal shoot also emerged from an axillary bud of the primary shoot or, sometimes, from an axillary bud of the first basal shoot. If a third basal shoot occurred, it originated from an axillary bud of a basal shoot. The buds, which became the first and second basal shoot, were already present as secondary buds in the axils of the scales of the axillary bud when used for propagation. During the development of this primary bud into the primary shoot the secondary buds continued to initiate new leaf primordia, but did not sprout until the growth of the primary shoot slowed down. Removal of these two secondary axillary buds in the primary bud resulted in less basal shoots per plant and the basal shoots developed from buds number 3, 4 or 7.