Shoots In Spring Research Articles

The Effect of the Time of Fruit Harvest on Flower Formation and Carbohydrate Contents in Shoots of Wase Satsuma Mandarin Trees

The effect of the time of fruit harvest and that of fruit removal in early-July on flower formation and carbohydrate contents were investigated in Wase satsuma mandarin trees. In the spring shoots of the bearing trees, the flower induction seemed to be retarded in comparison with the summer shoots in the July-defruited trees. Both in the defruited trees and the early harvested (mid-Oct.) trees, flower formation occurred earlier and increased markedly higher by mid-March in comparison with the customary harvested (mid-Nov.) and late harvested (mid-Dec. or mid-Jan.) trees. Starch accumulation in the shoots seemed to parallel flower induction. Our data in Wase satsuma mandarin indicate a clear effect of the fruit harvest before November on both flower formation and starch accumulation.

Flower Bud Induction of Sweet Orange Trees [Citrus sinensis (L.) Osbeck]: Effect of Low Temperatures, Crop Load, and Bud Age

Citrus flowering is a complex phenological process influenced by a number of interacting factors. Low winter temperatures are recognized as an important factor, but the flowering response has not been quantified under Variable natural conditions. A study was conducted to monitor the flower bud induction response of `Valencia' and `Hamlin' sweet orange trees [Citrus sinensis (L.) Osbeck] to naturally occurring winter weather conditions during the 1999 and 2000 seasons. The flowering response was quantified and related to shoot age, bud position along the shoot, local weather information, and crop load status. Results indicate that buds on previous summer shoots developed 2.52 and 3.59 to 1 flower on spring shoots, for `Hamlin' and `Valencia', respectively. In addition, buds at apical positions produced more flowers than buds located far from the apex. These basal positions buds required higher induction levels. Under Florida conditions, greater accumulation of hours of temperatures 11 to 15 °C increased floral intensity by the combined effect on the number of sprouting buds with reproductive growth and the number of flowers per flowering bud. Some statistical analyses indicated that high winter temperatures reduced flowering in `Valencia' and `Hamlin' oranges. The presence of fruit consistently reduced reproductive response for both cultivars. Crop load reduced flowering by an average of 41.5% compared to no crop and varied by cultivar. A discussion on the different induction requirements as well as on the differential effect of crop load on flowering by cultivar is presented.

Rooting of Cercis siliquastrum cuttings influenced by cutting position on the branch and indole-butyric acid

SummaryThe effects of cutting position within the source shoot and concentration of 1H-indole-3-butyric acid (IBA) or its potassium salt (K-IBA) on rooting in Cercis siliquastrum were assessed. Stem cuttings were taken from terminal or basal portions of the shoots in early spring, early summer, or winter and treated with 0, 24, 48, 72 or 96 mM IBA in 50% ethanol or K-IBA in water. Terminal cuttings were also treated with a commercial rooting powder containing 0.1, 0.3 or 0.8% IBA. Rooting was unsuccessful except when cuttings were taken in the summer. Percent rooting was not significantly affected by concentration of IBA, but terminal cuttings exhibited higher rooting (43%) than basal ones (13%). Length and dry mass of roots produced per rooted cutting were significantly increased with increasing concentration of IBA. Basal cuttings performed poorly irrespective of K-IBA concentration, whereas terminal cuttings treated with the higher concentrations (72 and 96 mM) exhibited greater rooting than those treated with the lower concentrations (0–48 mM). The highest rooting percentage (80%) was obtained at 72 mM K-IBA, but the shape of the response curve suggests that the optimum concentration is probably slightly above 96 mM, the highest concentration tested. The quantity of roots produced per rooted cutting was not affected by cutting position or K-IBA concentration. Treating terminal cuttings with 0.3 or 0.8% IBA powder resulted in 60% or 73% rooting, respectively. The slope of the response curve suggests that the optimum might be above 0.8%, the highest concentration tested.The quantity of roots was not affected by IBA powder concentration.

Relationship between Flower-bud Differentiation and Carbohydrate Contents in Spring Shoots of Very-early, Early and Late Maturing Cultivars of Satsuma Mandarin

Seasonal changes in the types of bud, vegetative, mixed or generative (reproductive), and carbohydrate contents in three satsuma mandarin (Citrus unshiu Marc.) cultivars, 'Yamakawa Wase', 'Okitsu Wase' and 'Aoshima Unshiu', were investigated. Shoots from these very-early, early and late maturing cultivars, respectively, were excised and examined for bud types from the pre-harvest period of the previous year to just before bud break in the spring (2001-2002). Tree growth of each cultivar in 2001 showed aspects of nearly the heaviest on-year of alternate bearing for the previous 10 years, so that a poor return bloom was expected in 2002. Shoots that sprouted in the spring of 2001 were sampled at monthly intervals from early-November to mid-March, 2002, defoliated, placed in a vase and sprayed with 100 ppm benzyladenine (BA) to force them into growth in a chamber kept at 28°C. After 8-14 days of incubation, developing buds were tallied whether they were vegetative, mixed or generative. In every cultivar, nearly all buds of shoots excised in early-November were vegetative; those with an inflorescence constantly increased up to mid-March. Shoots of 'Yamakawa Wase', whose trees were harvested in late-October, progressed from the vegetative to the generative phase most rapidly, followed by those of 'Okitsu Wase' and 'Aoshima Unshiu', whose trees were harvested in mid-November and mid-December, respectively. There was no significant difference in the bud types between 'Okitsu Wase' and 'Aoshima Unshiu' throughout the experimental period. From December to February, the starch concentrations in the spring shoots of 'Yamakawa Wase' were significantly higher than those of the other two cultivars. Spring shoots of 'Okitsu Wase' had the highest total sugar contents from December to January, but the least number of inflorescences. Higher total sugar accumulation in spring shoots after harvest seemed to have no promotive effect on flower-bud formation. Our data indicate that earlier harvest of satsuma mandarin induces rapid starch accumulation in spring shoots, resulting in a progressive differentiation of flower buds on inflorescences.

Long-term effects of yearly grazing by moulting Greylag geese ( Anser anser) on reed ( Phragmites australis ) growth and nutrient dynamics

In this study, the effects were quantified of grazing by moulting Greylag geese in spring on biomass and nutrient dynamics of monospecific stands of Phragmites australis. A comparison was made between a marsh which had been grazed for more than 15 years, and a site which had not been grazed for at least that period. Both marshes bordered the same lake. Net above-ground primary production (NAPP) and N and P allocation to above-ground parts were estimated for two growing seasons from regular measurements of the standing shoot biomass and its N and P content, and by using temporary exclosures during goose grazing. Annual NAPP was similar between grazed and ungrazed areas (1997) or higher in the grazed area (1999). Rhizome biomass was similar between areas but the timing of minimum biomass shifted from June to September with grazing. A higher spring shoot emergence due to lower standing dead mass in the grazed area and relocation of reserves from rhizomes to shoots were important in sustaining/increasing NAPP with grazing. Grazing by moulting Greylag geese in spring approximately doubled the annual allocation of N and P to shoots, and almost tripled the annual above-ground losses of these elements compared to an ungrazed reed vegetation. In the grazed area, 50% or more of the annual nutrient losses were due to goose activity, as no nutrients were resorbed from the nutrient-rich tissue that was consumed or torn and rejected. Differences in timing of shoot emergence in spring were important in affecting the extent of nutrient loss due to goose activity. The increased N and P losses as a result of grazing were associated with consistently lower N and P concentrations in the rhizomes, but only in 1999 were nutrient reserves in rhizomes over winter lower in the grazed reed stand. Resorption efficiency from senescent tissue was increased with grazing in 1997 but not affected in 1999. Our results indicate that grazing increased growth and nutrient dynamics of P. australis in this eutrophic reed marsh.

Annual shoot growth components related to growth of Pinus brutia.

Shoot elongation patterns of Pinus brutia Ten. were studied in six natural populations and 10 open-pollinated families within each population. The data were collected from a provenance-progeny trial that was thinned at Ages 13 and 17 years. Annual height increment was partitioned into first flush (spring shoot) and subsequent flushes (summer shoots) and the contribution of each to annual height increment was measured from Ages 7 to 17. Spring shoot elongation patterns were similar in all populations and families for 9 out of 10 years. In contrast, at all ages, populations differed significantly in total summer shoot growth and number of summer flushes. Families within populations differed in number of summer flushes in 7 out of 10 years. Summer shoot growth was the major cause of the differences in annual height growth among the six populations. Significant and high correlations were observed between summer shoot growth at Ages 7 to 12 and height at Age 13. A population from near the middle of the species' altitudinal range had more summer flushes than populations from higher or lower elevations, indicating an opportunistic growth pattern. Compared with mid-elevation populations, low- and high-elevation populations had more conservative growth patterns that depended mainly on growth of spring shoots. We conclude that summer shoot growth can serve as an explanatory variable to predict height growth of populations. Differences in shoot elongation patterns among Pinus brutia populations may be useful for selecting seed sources and for gene conservation programs.

Sustainability of New Zealand high‐country pastures under contrasting development inputs. 5. Nutrient pools and balances

The nutrient fluxes, pools, and balances for N, S, P, and Ca were estimated for two sheep‐grazed mixed species studies on a Pukaki/Tekapo high‐country soil from measurements during the 10–15 th years following initial development. One compared 30 combinations of 5 superphosphate rates (0–500 kg ha‐1 yr‐1) × 3 stocking rates × 2 stocking methods × 2 spatial replications; the other compared 27 combinations of P and S fertiliser (0–100 kg element ha‐1 yr‐1). The stock off‐take under zero fertiliser was 1.1,0.1,0.2, and 0.4 kg ha‐1 yr‐1 for N, S, P, and Ca, respectively. Fertiliser inputs exceeded stock off‐takes by 4–100‐fold in fertiliser treatments. The 10‐year stock off‐take was similar to the 1‐year spring shoot pool. C and N were principally in the soil fraction. Estimated N fixation was 150–223 kg N ha‐1 yr‐1 in the fertilised treatments. Increases in the components of the S pools in the shoots and soil to 40 cm accounted for 46–56% of the applied S in the dryland fertilised treatments and 21% in the irrigated high fertiliser treatment. Residual elemental S accounted for 11–21% of applied S. Much of the P and Ca were in the coarse organic matter pools. P and Ca pools did not increase in proportion to fertiliser rates. There was an apparent loss of total P to levels similar to double the applied fertiliser rates, possibly from change in datum sampling depth due to measured soil expansion. There was less than 2% movement of nutrients into sheep camps.

Recovery of experimentally created gaps within a tropical Zostera capricorni (Aschers.) seagrass meadow, Queensland Australia

The recovery of experimentally cleared plots in a meadow dominated by Zostera capricorni was monitored monthly by measurements of leaf shoot density and estimates of above-ground biomass from September 1995 to September 1996. The rate of recovery, relative importance of sexual and asexual reproduction and the role of the seed bank on recovery were examined by manipulating the supply of sexual and asexual propagules. Cleared plots were mostly recolonised by Zostera capricorni. Recolonisation occurred principally by asexual growth from surrounding rhizomes. There was no significant recovery by sexual means, although flowering and fruiting were observed during the study period from July through to December with the highest density of sexual shoots in early spring (109.7±24.4 shoots m −2). Seeds stored in sediments played no role in recovery. Above-ground biomass and shoot density in cleared plots where asexual regrowth was allowed recovered to the level of the uncleared controls after 12 months. Control (uncleared) plots showed distinct seasonality in above-ground biomass, peaking in spring (71.2±3.4 g DW m −2), but not in shoot density, indicating that shoots became smaller rather than less numerous in winter. The rate of asexual recovery slowed in autumn corresponding to the period of biomass decline in the control plots but rapidly increased in late winter and spring.

Involvement of endogenous plant hormones (IAA, ABA, GAs) in leaves and flower bud formation of satsuma mandarin ( Citrus unshiu Marc.)

Plant hormones (IAA, ABA, GA 1/3, GA 4/7) contents in the leaves of satsuma mandarin trees ( Citrus unshiu Marc. `Okitsu') were measured to elucidate the relationship between endogenous plant hormones and flower buds formation. The ringing treatment to lateral branch in October enhanced the percentage of leafless inflorescence and number of flowering shoots in the following spring. While, more vegetative spring shoots were formed on bearing shoots which were left the fruit load in the previous autumn to winter. GA 1/3 were the dominantly detected GAs in the leaves. Their content was higher in the leaves of the bearing shoots than in that of the vegetative shoot but was not affected by the ringing treatment. Ringing increased the percentage of leafless inflorescence and the contents of IAA and ABA in December. These results suggested that flower bud formation was inhibited by GA 1/3 in October, and that high IAA and ABA content in December also promote the percentage of leafless inflorescence and the number of flower buds per node. The relationship between endogenous plant hormones and flower bud formation was discussed.

Effect of Stalk Desiccation on Sugarcane Red Rot.

The effect of drought conditions at planting time on sugarcane red rot, caused by Colletotrichum falcatum, was evaluated in experiments conducted under controlled conditions and in the field. For experiments under controlled conditions, detached and topped mature stalks of five cultivars were inoculated with conidia of C. falcatum, then exposed to a 3-week desiccation treatment, followed by 3 weeks without desiccation, or maintained for 6 weeks without desiccation. Disease severity, assessed as the number of nodes beyond which rot symptoms extended, number of nodes rotted, internode rot severity, and a rot severity index, was increased in five cultivars by exposure to desiccation. However, response of individual cultivars varied for some disease traits assessed. In field experiments, C. falcatum inoculation alone did not reduce spring shoot populations for seven cultivars. The lowest shoot populations occurred in plantings of inoculated stalks exposed to desiccation. Some cultivars were adversely affected by desiccation alone. These results demonstrate that red rot severity can be increased by the occurrence of drought conditions during the initial growth processes of vegetatively propagated sugarcane stalks.

Excised canes are a suitable test system for the study of budbreak and flowering of kiwifruit canes

Kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson) canes were excised from vines during winter and suspended from the vine canopy in the field until late spring. The effects of excision, subsequent orientation of the cane, and length of the cane (whole cane or cuttings) on spring budbreak, shoot growth, and flowering were compared with equivalent intact canes left on the vine. Excision and orientation of whole canes had no effect on budbreak. Budbreak on small cuttings (80%) was greater than on whole canes (40%) or intact canes (45%). The sequence of budbreak was also different in small cuttings. Shoot development on excised canes and cuttings was limited; shoots were shorter, node number generally less, and flower bud size smaller. Numbers of flowers on shoots were the same on excised canes, cuttings, and intact canes. Small cuttings are only useful to predict the flower number potential of particular shoot buds. Excised canes form a suitable system for the study of interactions between buds on a cane involving measurements of budbreak, timing, and patterns of budbreak and/or numbers of flowers per shoot.

Off-season Production of Primocane-fruiting Red Raspberry Using Summer Pruning and Polyethylene Tunnels

The spring shoots of `Autumn Bliss' red raspberry (Rubus idaeus L. var. idaeus; primocane-fruiting type) were cut on 2, 16, 31 July and 15 and 30 Aug. with the objective of delaying fruit harvest into the off-season under mild winter climatic conditions. Cutting shoots in August delayed fruit harvest until February and April of the following year, but shoot growth was weak and fruit yield low (4.8 and 2.1 g/cane). July cuttings delayed harvest until October to January with acceptable fruit yield (63.5, 52.8, and 26.5 g/cane for 2, 16, and 31 July, respectively). The differences in cane height and total node and fruiting node count between the three cutting dates of July were small, but there was a constant decrease in leaf area per cane from the first to the third date and a sharp decrease in fruit yield from the second to the third date. Vegetative shoot growth was less affected than yield when summer cutting was delayed until the end of July to induce a later harvest. Fruit quality always reached acceptable standards. This study confirms the practicability of using summer-cutting of primocane-fruiting red raspberries to induce off-season fruit production under protected cultivation in mild winter climates.

An Examination of Resistance to Blighting and Fruit Infection by Monilinia vaccinii-corymbosi in Highhush Blueberry

Previous studies demonstrated a strong positive correlation between early spring shoot growth and susceptibility to the blighting phase of mummy berry. Plants with slow shoot growth derive resistance from avoidance but also may have biochemical resistance. Shoot growth of six highly resistant cultivars was artificially advanced, then plants were exposed to natural infection to assess disease response. Increased susceptibility with increasing shoot length was observed in most cultivars, although degree of response was variable. Within cultivars, there were increases in susceptibility up to shoot lengths of ≈20 mm, beyond which susceptibility decreased. Studies of fruit infection in 48 cultivars found a range of susceptibility and resistance, but little correlation between blighting and fruit infection resistance.

Seasonal Changes in Nonstructural Carbohydrates, Protein, and Macronutrients in Roots of Alfalfa, Red Clover, Sweetclover, and Birdsfoot Trefoil

Root total nonstructural carbohydrate (TNC) has been studied, but little is known about seasonal trends in proteins and other macronutrients in legume roots. Our objectives were to determine how winter hardening and resumption of growth in spring influence (i) concentrations of sugars and starch, and activities of amylases; and (ii) protein concentration and composition, and abundance of N, P, and K. Alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), birdsfoot trefoil (Lotus corniculatus L.), and biennial sweetclover (Melilotus officinalis L.) were seeded in rows in the field in May and roots were sampled at approximately monthly intervals in autumn and biweekly in spring. All species accumulated high root TNC and starch concentrations in autumn. Starch and TNC concentrations declined throughout winter, but increased in roots of alfalfa and red clover in May. Starch accumulation and degradation patterns in spring were correlated with root endoamylase activity. Root sugar concentrations increased threefold from October to November. Root N and soluble protein concentrations increased 50% between September and December, and declined between March and May. Specific proteins accumulated to high concentrations in alfalfa roots during autumn. Root P increased 50% between October and April and was associated with an increase in root phytate. Proteins, N, P, and phytate accumulated during winter hardening in autumn in roots of these forage legume species that, in conjuction with TNC, may supply nutrients to regrowing shoots in spring.

Grass yield in relation to potassium supply and the concentration of cations in tissue water

SUMMARYA long-term field experiment on permanent grass at Rothamsted (UK) was studied between 1988 and 1991 to determine the relationship between soil and plant K and to identify critical soil and plant concentrations for grass yield. Maximum dry matter yield was obtained at a soil exchangeable K concentration (Kex) of 114 mg/kg dry soil (45 μм-K in the soil solution). Grass well-supplied with K maintained an average concentration ofc.200 m м-K in the tissue water of whole shoots in spring, although individual measurements varied in the range 140–320 mм, depending largely on the soil water availability. These tissue concentrations were not exceeded in soils with Kexvalues up to 800 mg/kg. Yield was reduced by 60% on plots low in K (Kexin the range 60–90 mg/kg). The yield reductions were probably due to low turgor because tissue osmotic pressures were low and potassium concentrations in tissue water (which averaged 64 mм) were probably too high to disrupt the biochemical functions of K. The results suggest that there is no universal critical tissue water concentration for K in the biophysical role of turgor maintenance, as other cations and solutes are able to substitute for it. The ultimate determinant of turgor-dependent yield loss is tissue osmotic pressure. The critical tissue osmotic pressure in grass shoots in a typical season at Rothamsted wasc.400 mosm/kg. No universal critical osmotic pressure can be expected however, as this will depend on the availability of water and therefore on growing conditions.

Effects of Artificial Leaf Cutting on the Shoot Production of Lithocarpus edulis and Three Other Evergreen Species in Relation to Phytophagous Insects

Effects of artificial leaf cutting on the production of normal and "lammas" (defoliation-compensating) shoots were compared among Lithocarpus edulis (Fagaceae) and 3 other evergreen species in Kagoshima. The lammas shoots were produced abundantly in L. edulis. Some bivoltine and multivoltine phytophagous insects may be supported by these unpredictable and less abundant shoots. It is remarkable that a univoltine species of gall midge, Tokiwadiplosis matecola, uses the lammas shoots for galling instead of normal spring shoots.

Effects of paclobutrazol on phenological cycling of low-chill ‘Flordaprince’ peach in subtropical Australia

Low chill ‘Flordaprince’ peach trees were grown in subtropical Australia, either following two paclobutrazol applications to dwarf the trees, or nitrogen to invigorate them. Following blossom thinning, the number of fruits per tree was adjusted to give a uniform number of well-spaced fruits per tree. Paclobutrazol significantly reduced the competing spring shoot growth and resulted in earlier maturity of a greater crop of larger, better quality fruits. It also reduced the spring flush of root growth. but resulted in a greater autumn root flush. Stage 2 of fruit growth was slightly longer in the Vigorous trees, resulting in delayed seed and embryo growth and greater dry mass of the embryos. Starch reserves were shown to be greatest in the roots, followed by the trunk, shoots and leaves. The reserves dropped to their lowest levels during the stone hardening and fruit maturation stages, but rose after the end of shoot extension growth to reach a peak again by leaf fall. Leaf analysis showed that N, P and K concentration decreased through the season, while Ca and Mg increased. There were significantly lower K, and higher Ca and Mg levels in paclobutrazol treated trees.

PHENOLOGY OF LOW-CHILL `FLORDAPRINCE' PEACH

Low chill `Flordaprince' peach trees were grown in subtropical Australia, either following paclobutrazol application to dwarf the trees, or extra nitrogen to invigorate them. Fruits were thinned uniformly. Paclobutrazol significantly reduced the competing spring shoot growth and gave earlier maturity of larger, better quality fruits. It reduced the spring, but increased the autumn root flush. Stage 2 of fruit growth was slightly longer in vigorous trees, resulting in delayed seed growth and greater dry mass of the embryos. Starch reserves were greatest in the roots, followed by the trunk, shoots and leaves. The reserves were lowest during the second half of fruit development, but rose again after the end of shoot extension growth. Leaf N, P, and K levels decreased through the season while Ca and Mg increased. There were significantly lower K and higher Ca and Mg levels in dwarfed trees.

Effects of polyethylene film cover on the maturation and quality of ‘Fuyu’ persimmon fruit in New Zealand

Abstract Partially covering a block of ‘Fuyu’ persimmon trees with polyethylene (plastic) cover increased fruit colour, weight, soluble solids concentration, and lowered soluble tannins in each of two seasons. These improvements to fruit quality may have been the result of higher temperatures in the block partially covered with plastic. Plastic covering also increased spring shoot growth and advanced flowering by 7 days. The beginning of harvest was advanced by 1 week, and the spread of harvest reduced by 10 days. The effects of plastic covering on fruit quality varied between seasons. The increases in fruit colour and soluble solids concentration were greater in 1989 than in 1990. The increase in fruit weight and the decrease in soluble tannin content were greater in 1990 than in 1989.

Storage Proteins in the Wood of Taxodiaceae and of Taxus

Using SDS-PAGE, a prominent polypeptide of ca. 35 kDa was found in the wood extract of Taxodium distichum . It disappeared during growth of new shoots in spring and accumulated again in fall, suggesting its significance in protein storage. Antibodies raised against this protein also showed strong immunochemical reaction with proteins of 32 and 34 kDa extracted from the wood of Metasequoia glyptostroboides . In contrast, the evergreen species Sequoiadendron giganteum did not give a positive immunological response at the fall stage investigated, while two polypeptide bands of about 34 and 36 kDa of Taxus were slightly but significantly positive against this anti-35 kDa protein antibody of Taxodium . The widespread occurrence of possibly closely related storage proteins thus is indicated.