Renewal Shoots Research Articles

Comparative organogenesis of the species of the genus Hosta Tratt

For the first time, a comparative analysis of organogenesis in Hosta species - H. decorate, H. sieboldiana, and H. lancifolia in the forest-steppe zone of Western Siberia was performed. It was found that the intrarenal formation of generative organs in these species is laid during the growth of monocarpic shoot in May- June. Differentiation of the growth cone of the renewal shoot occurs synchronously from stages III to VIII of organogenesis for 56-91 days. In the early-flowering species H. decorate, the organ-forming process occurs 25 - 27 days faster than in the late-flowering H. lancifolia. Generative organs in the rudimentary inflorescence are formed acropetally. Stages of organogenesis from IX to XII correspond to phenophases from the beginning of flowering to fruiting. In the pre-winter period, the cone of growth of the renewal shoot in all species is at the II stage of organogenesis, with 4 to 6 leaf metamers embedded in its basal part.

Biological features of Iris setosa in the forest-steppe zone of Western Siberia

The seasonal rhythm of development of Iris setosa during the growing season of 2016–2018 in the conditions of the forest-steppe zone of Western Siberia is analyzed. It was determined that in the pre-winter the cone of growthof the renewal shoot forms vegetative organs-leaves, which corresponds to the second stage of organogenesis. Differentiation of the growth cone of the shoot to generative organs begins in early spring in May during a period of intensivegrowth. Within 14–15 days, the growth cone undergoes intrarenal development from stages III to VIII of organogenesis.IX–XII stages of organogenesis correspond to phenodates from flowering to fruiting. The duration of flowering is 10–25days. Plants undergo a full cycle of seasonal development from regrowth to fruiting, have high cold resistance, resistanceto diseases and pests. In the forest-steppe zone of Western Siberia, the adaptive potential of I. setosa is 23–30 points. Itwas found that according to the adaptation criteria, highly promising plants of I. setosa from the Trans-Baikal population.

Stub Length and Stub Angle Did Not Influence Renewal Shoot Number or Branch Angle of Tall Spindle ‘Gala’/Malling 9 Apple Trees

Renewal of limbs by pruning to leave a short, angled, upward-facing stub is common practice for spindle-type apple (Malus ×domestica) training systems. A short, beveled stub cut is thought to stimulate renewal growth from latent buds present underneath the base of the excised branch, and to stimulate smaller, more fruitful renewal limbs with wide crotch angles. We conducted trials over the course of 2 years that involved dormant pruning of ‘Buckeye Gala’ with renewal cuts to compare two stub lengths, 0.5 and 2 cm, and three stub orientations, upward facing, downward facing, and vertical facing, to determine the effects on renewal shoot number, position, angle, and length. We found no clear advantages with either stub length that we evaluated, and there was no improvement in renewal shoot quality with a bevel cut at any orientation. Stub length and stub angle did not influence limb renewal and may be unimportant for training orchard-pruning crews and for machine-learning and robotic pruning.

Canopy Separation Did Not Improve Dry-on-Vine Raisin Yield or Quality from Selma Pete Grapevines on Open Gable Trellises

Summary Goals: Dry-on-vine (DOV) raisin growers with open gable trellises can use selective cane-pruning and shoot positioning to separate grapevine canopies into distinct fruiting and renewal zones. This practice is thought to improve canopy structure and microenvironment, increasing raisin yield and quality. However, these assumptions have not yet been confirmed by research. Therefore, an experiment was conducted in which Selma Pete grapevines ( Vitis vinifera ) on open-gable trellises were subjected to one of three canopy separation treatments: non-separated; center-divided, where renewal shoots were gathered in the trellis center and supported by a foliage catch wire; or within-row alternate-bearing (WRAB), where selective pruning left canes and spurs on opposite cordons. The effects of canopy separation treatments on canopy structure, microenvironment and raisin yield, and quality were followed for three years. Key Findings: The WRAB canopy separation method generally reduced the number of leaf layers and increased the proportion of leaves on the canopy exterior in renewal shoot zones. In spring, renewal shoots in WRAB canopies had more direct sun exposure than renewal shoots in other canopy types, but light levels in WRAB canopies diminished thereafter, becoming similar to those in other canopies. Despite effects on canopy structure and microenvironment, no canopy separation method tested affected raisin yield or quality consistently. Impact and Significance: The WRAB canopy separation method affected canopy structure and microenvironment, but insufficiently to increase the yield or quality of DOV raisins on an open gable trellis. Moreover, the selective pruning required to establish WRAB canopies may reduce yield in the season following establishment, and possibly have negative effects on the fruiting zone microclimate, hindering fruit ripening or drying.

Leaf Development, Metamorphic Heteroblasty and Heterophylly in Berberis s. l. (Berberidaceae)

Shoot development of temperate and tropical members of Berberis s. l. was examined in order to assess: (1) the homology of the spines along the long shoots and the foliage leaves that form on the short shoots; (2) the occurrence of heterophylly and/or heteroblasty in the genus; and (3) the structural correspondence between cataphylls, spines, and foliage leaves. The 1-5-armed spines have been interpreted as modified compound leaves lacking stipules, as a modified lamina (central spine) with stipules (lateral spines), or less often, as transformed branches, or as epidermal outgrowths. On the other hand, the foliage leaves of the short shoots have been interpreted as leaflets of palmately compound leaves. Our results indicate that there are three distinct leaf types per node: (1) Leaves modified in spines spirally arranged in long shoots; (2) foliage, expanded leaves densely arranged in short shoots; and (3) cataphylls protecting axillary buds. The spines are leaf homologs with a clear distinction between the leaf base with stipules, and a laminar portion modified into the 1-5-armed spine; the lateral spines are not stipules as they arise from the marginal meristem of the laminar portion, and not from the leaf base. The foliage leaves also have stipules flanking the leaf base. Both spiny leaves and foliage leaves develop an articulation between the base and the laminar portion. Cataphylls of the short shoots of Berberis s. str. and those of the reproductive short shoots of Mahonia correspond to the entire leaf base, but those of the renewal (vegetative) shoots of Mahonia are spiny and have an odd vestigial pinnately compound lamina. Heterochrony due to ontogenetic truncation caused by the formation of the terminal inflorescence at the apex of the short shoots could be responsible for the lack of petiole/lamina differentiation in the foliage leaves. The spiny long-shoot/foliose short-shoot system of branching in Berberis s. str. appears to be genetically and phylogenetically fixed and not environment-dependent. This represents a clear example of metamorphic heteroblasty sensu Zotz et al. (Botanical Review 77:109–151, 2011) with further occurrence of heterophylly along the short shoots.

Early-ripening Grapevine Cultivars for Dry-on-vine Raisins on an Open-gable Trellis

‘Diamond Muscat’, ‘DOVine’, ‘Fiesta’, and ‘Selma Pete’ grapevines (Vitis vinifera) were evaluated to determine their suitability for making dry-on-vine (DOV) raisins on an open-gable trellis. The experiment was a split-plot, with training system, head, bilateral, or quadrilateral cordons as the main plot, and grapevine cultivar (Diamond Muscat, DOVine, Fiesta, or Selma Pete) as the subplot. Yield components, fruit composition, and raisin yield and quality were evaluated annually. Vine training style did not affect fruit composition, or raisin yield or quality, but vines trained to quadrilateral cordons produced more clusters on renewal shoots than head-trained vines. ‘DOVine’, ‘Fiesta’, and ‘Selma Pete’ produced about 4.75 tons/acre of raisins, ≈10% more than ‘Diamond Muscat’. ‘Diamond Muscat’ vines produced the most clusters on renewal shoots, an undesirable trait, and the most clusters per vine. ‘Fiesta’ matured later than the other cultivars, therefore it had the lowest soluble solids, the poorest raisin grades, and the highest field moisture at harvest. ‘Selma Pete’ grapes matured as early, or earlier, than the grapes of other cultivars, they had among the highest soluble solids and raisin grades, and the raisins generally dried well. Thus, ‘Selma Pete’ grapevines had the best overall performance of the cultivars tested.

An architectural model for Eleocharis: morphology and development of Eleocharis cellulosa (Cyperaceae)

Species of Eleocharis are prominent in aquatic and wetland habitats and serve as models for study of physiological adaptations to aquatic environments. The genus has an unusual morphology because the major photosynthetic organ is the stem. In order to define an architectural model for the genus to understand the evolution of this morphology, we examined mature morphology and development of E. cellulosa in living and fixed material using light and scanning electron microscopy. Eleocharis cellulosa has sympodial, vertical shoots that produce the photosynthetic culms and horizontal shoots that mix monopodial and sympodial development. Each sympodial unit produces three bracts, an elongated photosynthetic internode, then a fourth bract and an inflorescence that either aborts on vegetative culms or expands on reproductive culms. On each sympodium, the first bract subtends a precocious axillary bud that reiterates the sympodial unit; the second bract subtends a bud that develops the horizontal shoot. In both horizontal and vertical shoots, the internode below the second bract is produced by both the second bract and the renewal shoot. Sympodial growth is present in seedlings. In other species of Eleocharis, the structure of the sympodial unit is conserved but morphological diversity develops from variation in horizontal shoot growth.

SHOOT MORPHOLOGY IN THE CLAYTONIA SIBIRICA COMPLEX (PORTULACACEAE)

ABSTRACT The Claytonia sibirica complex, including C. sibirica and C. palustris, exhibits considerable morphological variation that encompasses ecological diversity over a wide geographic range. Shoots are basically rhizomatous in the complex and least specialized in C. sibirica var. sibirica. Claytonia sibirica var. bulbillifera, a serpentine endemic of southern Oregon and northern California, forms succulent, storage scale leaves distal to its foliage leaves each growing season. These scale leaves, which consist primarily of leaf base, are generally lacking in other members of the sibirica complex and give the shoot systems of C. sibirica var. bulbillifera a bulb morphology. Claytonia palustris, like C. sibirica var. sibirica, forms an apically swollen rhizome, but differs in its habit by forming renewal shoots, born in the axils of the basal leaves, at the ends of plagiotropic, single long internodes.

Effects of Harvest Pruning on `Thompson Seedless' Grapevines

In response to diminishing returns, the California raisin industry is rapidly adopting mechanical raisin harvesting practices to reduce cost. Whether the fruit will dry on the vine, or be laid on continuous trays to dry, the first step of mechanical raisin harvest generally involves severing the canes of vines with ripe fruit, a practice known as harvest pruning (HP). The potential physiological implications of HP are uncertain, so an experiment was established to assess the effects of HP on 40-year-old `Thompson Seedless' grapevines (Vitis vinifera L.) that were on their own roots, head-trained and cane pruned, and supported by a single wire trellis. Fruit achieved 20 °Brix by 2 Sept., at which time vines had a leaf area of about 21.6 m2. About 60% of the canopy leaf area was from canes, and thus removed by HP. The net CO2 assimilation rate (A) of mature leaves on renewal shoots began to decline after about 8 Aug., but they maintained a positive A until at least 31 Oct. Reduced A was due, in part, to chlorophyll degradation as evidenced by a decline in SPAD units occurring over the period that A declined. Harvest pruning generally did not affect A of mature leaves retained on renewal shoots, but those leaves maintained a positive A for at least 60 d after HP indicating that HP reduced the vines' photosynthetic capacity. Soil respiration also declined between summer and winter, probably in response to decreasing soil temperatures. Soil respiration was similar among HP and non-HP vines, except about 30 d after HP, when HP vines had about 30% lower soil respiration values than non-HP vines. Root growth was observed in summer and fall regardless of whether vines were subjected to HP.

Canopy Separation and Defoliation for Dry-on-the-vine (DOV) Raisins on Traditional Trellises

Pruning efficiency, fruitfulness, and yield and quality of raisins of `Thompson Seedless' (Vitis vinifera L.) grapevines subjected to several canopy separation and defoliation treatments for DOV raisin production were evaluated. Canopy separation treatments, tested in vineyards at Easton, and at the Kearney Agricultural Center (KAC), Parlier, Calif., were as follows; horizontal canopy separation with vine sections of fruiting or renewal zones (Peacock), horizontal canopy separation with vine sections of fruiting zones of one vine adjacent to renewal shoots of the next vine (wave), or non-separated (control). Defoliation treatments included burning or blowing leaves (Easton), application of concentrated solutions of calcium ammonium nitrate or Etherel to leaves (KAC), or no defoliation (both vineyards). Canopy separation treatments did not affect berry size, soluble solids, or raisin yield. Vines subjected to Peacock training had more cluster layers than vines subjected to wave training, at Easton, and more cluster layers than vines subjected to control training at KAC. Canopy separation reduced harvest pruning time by 20% at Easton, but not at KAC. No treatments affected raisin moisture at Easton but, at KAC, raisins of vines trained in the Peacock style had 10% higher moisture contents at harvest than raisins of wave or control vines. Vines subjected to conventional training and leaf blowing had about 40% higher “B and better” raisin grades than vines with separated canopies that were not defoliated, and about 30% higher grades than vines with conventional training and leaf burning. However, raisins of vines subjected to blowing had about 60% more mold than raisins of non-defoliated vines. Defoliation treatments at KAC did not affect any variables measured.

Heteroblasty and preformation in mayapple, Podophyllum Peltatum (Berberidaceae): developmental flexibility and morphological constraint

Developmental preformation can constrain growth responses of shoots to current conditions, but there is potential for flexibility in development preceding formation of the preformed organs. Mayapple (Podophyllum peltatum) is strongly heteroblastic, producing rhizome scales, bud scales, and either a single vegetative foliage leaf or two foliage leaves on a sexual shoot. To understand how and when preformation constrains growth responses, we compare (1) how leaf homologs of the renewal shoot differ in development, (2) whether there are differences in shoot development that occur in advance of morphological determination of shoot type, and (3) whether there are points of developmental flexibility in renewal shoot growth prior to preformation of the foliage and floral organs. We use scanning electron microscopy and histology to show that the three vegetative leaves (both types of scale leaves and the vegetative foliage leaf) are similar in the initial establishment of an encircling and overarching leaf base. Differences among them are found in the timing of differentiation of the leaf base and in the relative timing and degree of growth of the lamina and petiole. In contrast, foliage leaves on sexual shoots show less expression of the leaf base and precocious growth of the lamina and petiole. Prior to shoot type determination, there are no morphological differences in the sequence or position of leaf homologs that predict final shoot type. In this colony, leaves at positions 12 and 13, on average, appear to be identical in development until they are between 700 and 800 μm in length, when it becomes possible to distinguish leaves that will become vegetative foliage leaves from additional bud scale leaves on vegetative or sexual shoots. We suggest that late developmental determination of leaves at positions 12 and 13 reflects ontogenetic sensitivity to a transition to flowering. Thus, in mayapple, heteroblasty appears to facilitate developmental flexibility prior to the point where shoot growth becomes constrained by preformation of determined aerial structures.

Changing sink strengths influence translocation of phosphonate in avocado (Persea americana Mill.) trees

Translocation of phosphonic acid (H3PO3) in cv. Hass avocado trees was studied after trunk injection with 20% H3PO3, formulated as potassium phosphonate, at three stages of tree phenology during the growing season. Initially, translocation was solely acropetal in the xylem, and H3PO3was detected in the leaves 24 h after treatment. Several days after injection, H3PO3concentration in the bark of trunks and in roots increased, indicating basipetal phloem transport of H3PO3from leaves. The rate of accumulation and the final concentration of H3PO3in the roots were directly related to the sink strength of the shoot at the time of injection. For example, trunk injection at the beginning of spring growth flush, when renewal shoots were strong sinks, resulted in low H3PO3root concentrations (<9 8g gfw-1) which peaked about 45 days after treatment. When potassium phosphonate was injected after the transition of spring-grown shoots from sinks to sources, or at summer shoot maturity, root concentrations of H3PO3increased to >25 8g gfw-1 by 30 days after treatment. These results suggest that strategic timing of injections according to phenological events may greatly improve fungicide efficacy when targeting specific organs for protection.

Evaluation of sampling methods for harvesting non-treated and hydrogen cyanamide treated kiwifruit vines

From 1986 through to 1992 kiwifruit ( Actinidia deliciosa cultivar ‘Hayward’) from vines in the Bay of Plenty district of New Zealand, trained on a T-bar trellis with an upper wire to support renewal shoots, were harvested from various sections of vines and graded separately. For any variable, the effectiveness of grading only part of a vine was measured by R 2, the proportion of the variation in the true whole vine value that was accounted for by the estimate from the part vine. Grading fruit from ten long canes on the western side or all of the fruit on quarter vines gave R 2 values of approximately 0.6. R 2 values varied from 0.7 to 0.85 for half vines. Grading diagonal quarters was slightly better than using the east or west sides which were in turn marginally better than grading the north or south sides. In all of these cases the estimate was improved greatly when the part harvested was adjusted upwards by a scaling factor of the fruit weight on the whole vine divided by the fruit weight on the part graded. On hydrogen cyanamide treated vines, the west side of vines performed significantly better than the east side. This meant that a grading procedure based on one of these sides alone would be biased and could result in up to 22% error for vines growing on T-bars. Grading either the north or south side alone and adjusting by the fruit weight ratio was more satisfactory as the differences in fruit size at harvest were smaller between the north and south sides than between the east and west sides. In trials involving consecutive hydrogen cyanamide treatment of vines over five seasons, significant differences between the north and south sides of vines were observed in only one season but scaling by fruit weight overcame the problem.

Taxonomic Notes on Mesoamerican Annona Section Atta (Annonaceae), including Annona pruinosa sp. nov.

A new species of Annona sect. Atta from the upper altitudinal limit of the Pacific dry forest of Nicaragua and Costa Rica is proposed based upon a distinctive abaxial leaf epidermis. In addition, the analysis of flowers discovered for Annona longipes necessitates its transfer to section Atta. During preparation of treatments of the Annonaceae for the Flora de Nicaragua and the Manual to the Plants of Costa Rica, a new species of Annona L. sect. Atta C. Martius has been identified based on material from Nicaragua and Costa Rica. In addition, recent flowering collections of Annona longipes Saff. from Veracruz, Mexico, reveal its incorrect placement by Safford (1913) in section Pilannona Saff., and indicate its proper placement in section Atta. Annona (section Atta C. Martius) pruinosa Schatz, sp. nov. TYPE: Nicaragua. Carazo: Finca de Minco Cabrales, 700 m al sur del reloj, 18 June 1982 (fl, fr), L. Reyes V. 64 (holotype, MO; isotype, HNMN). Figure 1. A speciebus aliis Annonae sectionis Attae laminis subtus pruinosis differt. Tree to 10 m tall; young branches very sparsely white-tomentose, at length glabrescent. Petiole 0.81.3 cm long, slender, deeply canaliculate, very sparsely tomentose, drying black; lamina chartaceous, elliptic to obovate-elliptic, 6.4-15 cm long, 3.2-8.3 cm broad, the base cuneate to obtuse, the apex acute to rounded, the upper surface glabrous, the lower surface granular pruinose and initially sparsely white-puberulous, at length glabrescent, the venation eucamptodromous with 9-14 secondary veins per side, the primary vein slightly impressed adaxially, prominently elevated and sparsely golden puberulous, as are the slender secondary veins, abaxially. Flowers solitary, terminal but appearing leaf-opposed or supra-axillary by displacement during growth of the renewal shoot; pedicel slender, 1.3-2.4 cm long, to 3.1 cm long, 0.2 cm diam. and becoming rigid in fruit, white-tomentose, bearing a minute bract 0.8-0.9 cm from the base; sepals triangular, 0.2-0.3 cm long, 0.3 cm broad, the apex acute, densely white-tomentose; petals 3 (the outer petal whorl only, the inner whorl absent or at most represented by tiny vestigial petals), fleshy, triquerous, narrowly oblong-elliptic, 1.8-2.4 cm long, 0.5-0.8 cm broad, the apex acute to obtuse, the base concave inside, the outer surface white-sericeous toward the base, becoming sparsely puberulous toward the apex, the inner surface densely tomentose; stamens numerous, 1 mm long, the connective expanded truncate discoid, minutely papillose, yellow, contrasting with the white thecae; carpels 25-36. Fruit syncarpous, subglobose to broadly ovoid, to 4.5 cm long, to 4.5 cm diam., the apex rounded, the surface initially areolate, but then smooth with no evidence of the individual carpels at maturity, green, or light and dark green mottled, initially puberulous, at length glabrescent; seeds flattened ellipsoid-obovoid, to 1.6 cm long, 0.9 cm broad, 0.6 cm thick, the seed coat very thin, smoothreticulate, light brown. Paratypes. COSTA RICA. GUANACASTE: Parque Rinc6n de la Vieja, Hacienda Santa Maria, sendero a las pailas, 10?48'N, 85010'W, 700-800 m, 13 Aug. 1987 (fr), G. Herrera 693 (CR, MO); El Mirador, Rio Negro, 10047'40N, 85018'35W, 1 Oct. 1990 (fr), G. Rivera 679 (CR, MO). PUNTARENAS: San Luis, Monteverde, Rio Guacimal, 10016'N, 84?49'W, 700 m, 24 June 1988 (fr), Bello et al. 24 (CR, MO, U), Cant6n de Puntarenas, Monteverde, cliff edge on Pacific slope, Bajo Tigre trail, 10018'N, 84048'W, 900 m, 20 Oct. 1990 (fr), Haber & Zuchowski 10110(CR, MO), 27 Dec. 1991 (fr), Schatz et al. 3230 (MO). NICARAGUA. CHONTALES: ca. 2.8 km above (N of) Cuapa, ca. 12017'N, 85023'W, 400-500 m, 4 Sep. 1977 (fr), Stevens 3634 (HNMN, MO, WIS); 2-3 km NE of Cuapa, 12?17'N, 85?22'W, 400 m, 24 Sep. 1983 (fr), Nee & Sebastian 28486 (HNMN, MO, WIS). BOACO: Las Pitas, carretera a Camoapa (No. 19), 12?28'N, 85?35'W, ca. 400 m, 29 Aug. 1981 (fr), Moreno 10651 (HNMN, MO). Distribution and habitat. Annona pruinosa is known from southern Nicaragua and the Pacific slope of the Tilaran range in northwestern Costa Rica, in moist forest between 400 and 800 m, i.e., the upper altitudinal limit of the Pacific dry forest. The affinities of Annona pruinosa within section Atta lie probably with several Caribbean species (A. urbaniana R. E. Fries, from Haiti; A. praetermissa Fawcett & Rendle, from Jamaica; and A. cubensis NOVON 2: 249-251. 1992. This content downloaded from 157.55.39.124 on Fri, 13 Jan 2017 18:13:08 UTC All use subject to http://about.jstor.org/terms

Morphology of Dianthoveus cremnophilus (Cyclanthaceae)

Dianthoveus cremnophilus exhibits terminal inflorescences and rhizomes composed of renewal shoots. A rhizome bears two kinds of vegetative buds directly, viz. renewal buds that form renewal shoots and nonrenewal buds that may develop into new rhizomes. Adult leaves consist of sheath, petiole, transition zone, and a bifid lamina that varies from unicostate to subtricostate. The inflorescence axis consists of peduncle and spadix and bears two kinds of spathes, conspicuous and inconspicuous. Seeds exhibit four outer cell layers and become split periclinally throughout the third layer, as well as longitudinally down to this layer, along one edge. Tissue outside the region of splitting may be abscinded; wall ingrowths of the ruptured third layer adhere to, and appear outermost on, the remaining portion of seed, where they directly contact the environment. Seedlings exhibit a primary root, very short hypocotyl, cotyledon, and epicotyl with plumular leaves. Shoots manifest substantial mirror-image symmetry.

Inflorescence Position as a Taxonomic Character in the Cyclanthaceae

Studies of 47-49 species of Cyclanthaceae indicate that inflorescence position and shoot morphology are taxonomic characters that aid in identifying specimens within the family, both in the field and laboratory. In all studied species of Carludovica, Cyclanthus, and Evodianthus, inflorescences are terminal, and individual rhizomes are composed of renewal shoots, whereas in Asplundia, Dicranopygium, Ludovia, Schultesiophytum, Sphaeradenia, Stelestylis, and Thoracocarpus, only axillary inflorescences and rhizomes lacking renewal shoots are known. Axillary inflorescences exhibit a prophyll (adaxially situated, bicarinate scale leaf) basally on the peduncle. In species with terminal inflorescences, prophylls form on rhizomes. In certain species of six genera, inflorescences may form a cluster axillary to a rhizome-borne leaf. The commonality and broad taxonomic distribution of axillary inflorescence clusters among extant Cyclanthaceae indicate that they represent a primitive feature within the family.

Morphology, Growth, and Vasculature of the Sympodial Rhizome of Smilacina racemosa (Liliaceae)

A time-course study of shoot development in Smilacina racemosa was combined with an analysis of the vascular anatomy to investigate how adjacent sympodial units in the perennial rhizome are structurally related to one another. Organogenesis is seasonal and occurs over a period of 20 mo; leaves and flowers are preformed in miniature 8-12 mo before they fully expand. One lateral bud on the horizontal rhizome is initiated eccentric of the normal plane of distichy toward the lower side of the stem and develops as the renewal shoot. The vascular connection between the renewal shoot and the parent axis is complete; all but 2% of the central bundles of the parent axis directly enter or branch into the renewal shoot. Two features contribute to the completeness of the connection: (1) increased anastomoses of vascular bundles within the branch junction, and (2) the development of special girdling bundles that attach circumferentially to the parent axis. The vascular supply of dormant lateral buds is incomplete; roots attach only to the peripheral region of the central cylinder. The complete connection between adjacent sympodial units allows for a high level of physiological integration within the rhizome, while the restricted circumferential attachment of root traces may significantly influence the hydraulic pathway through the plant.

Developmental Potential of Axillary Buds of Water Hyacinth, Eichhornia crassipes Solms. (Pontederiaceae)

Buds axillary to foliage leaves of water hyacinth can elongate either as vegetative stolons or as renewal shoots produced in association with the terminal inflorescence. Stolons differ from renewal shoots in position within the shoot system, morphology, and function. Renewal shoot buds always expand, whereas stolon buds may or may not. A stolon bud develops in conjunction with the subtending leaf; as that leaf matures, the stolon bud reaches a critical period in development. At this point, the bud either continues to expand, producing a stolon, or it stops growth and matures. Maturation is not irreversible, but the probability of a bud expanding decreases as bud age increases. In the field, buds on plants at the water hyacinth mat edge frequently produce stolons, whereas buds on plants inside the mat rarely do so. Leaf morphology also varies between plants in these two regions of the mat. The particular association of leaf and branch type found in the field, however, can be reversed experimentally, indicating that although leaf and bud development are coordinated, the particular course of each is independent.

DEVELOPMENTAL POTENTIAL OF AXILLARY BUDS OF WATER HYACINTH, EICHHORNIA CRASSIPES SOLMS. (PONTEDERIACEAE)

Buds axillary to foliage leaves of water hyacinth can elongate either as vegetative stolons or as renewal shoots produced in association with the terminal inflorescence. Stolons differ from renewal shoots in position within the shoot system, morphology, and function. Renewal shoot buds always expand, whereas stolon buds may or may not. A stolon bud develops in conjunction with the subtending leaf; as that leaf matures, the stolon bud reaches a critical period in development. At this point, the bud either continues to expand, producing a stolon, or it stops growth and matures. Maturation is not irreversible, but the probability of a bud expanding decreases as bud age increases. In the field, buds on plants at the water hyacinth mat edge frequently produce stolons, whereas buds on plants inside the mat rarely do so. Leaf morphology also varies between plants in these two regions of the mat. The particular association of leaf and branch type found in the field, however, can be reversed experimentally, indicating that although leaf and bud development are coordinated, the particular course of each is independent.

Plant management of greenhouse roses. Formation of renewal canes

Renewal shoot (“bottom break”) formation in rose plants was affected by the temperature and relative humidity in the greenhouse. The number of shoots and the rate of their renewal were significantly higher in plants grown in a greenhouse cooled by evaporative coolers then in an uncooled greenhouse. A decrease in renewal shoot formation occurred which reduced light intensity above the stem base. This phenomenon was also observed in defoliated plants.