Termination Of Shoot Growth Research Articles

СЕЗОННЫЙ РОСТ ВИДОВ ABIES MILL., ИНТРОДУЦИРОВАННЫХ В БОРЕАЛЬНОЙ ЗОНЕ (КАРЕЛИЯ)

The study of the growth of the introduced species of Abies was carried out in the Botanical Garden of Pet-rozavodsk State University (middle taiga subzone, southern Karelia). Studies have established that the growth of shoots of species of the genus Abies begins at the same time in years with a friendly spring. In years with a protracted spring, differences between species in the timing of the onset of this phenophase can reach 1 week. The differences in the timing of the termination of shoot growth also do not exceed 1 week. Growth culminates first in A. holophylla, and most recently in A. balsameа. The highest value of the maximum growth is characteristic of A. holophylla, in other species it is 10–20% less. It turned out that the beginning and culmination of growth in them mostly depends on the temperature regime of the air. The air humidity and the amount of atmospheric precipitation constantly exceed the optimal value for this process. It was found that the beginning of the growth of the needles of the studied species of the ge-nus Abies is noted in late May-early June. The differences do not exceed 2−4 days. First of all, the culmi-nation of the growth of needles is noted in A. holophylla and A. concolor. Its value in these species is 1.5–2 times higher than in other species. Studies have shown that the timing of the beginning, culmina-tion and end of needle growth under the influence of environmental factors from year to year can vary within 2–18 days. The beginning of the growth of needles depends on the temperature regime of the air, and the growth dynamics, in addition, on the humidity of the air and atmospheric precipitation. The na-ture and degree of influence of environmental factors on the growth of needles varies very slightly from year to year, but differs markedly in the studied species of the genus Abies. It was found that A. sibirica and A. balsamea should be recognized as the most promising for landscaping settlements in settlements (with a low degree of pollution by pollutants).

The effect of the graft union on hormonal and ionic signalling between rootstocks and scions of grafted apple (Malus pumila L. Mill.)

The transport of chemical signals between rootstocks and grafted scions is implicated in the dwarfing capacity of apple (Malus pumila) rootstocks. This study investigated whether the intensity of putative ionic and hormonal signals between a dwarfing rootstock (M.9) and a semi-invigorating rootstock (MM.106) grafted with ‘Queen Cox’ scions was altered by the graft union. The capacity of rootstocks with different dwarfing potential for polar auxin transport (PAT) was also compared. Split-top pressure chambers were used to collect xylem sap samples at a range of flow rates from above and below the graft union in composite M.9 and MM.106 trees. Concentrations of hormones, anions and cations were quantified in expressed xylem sap. The effects of the graft union, flow rate and rootstock on xylem sap solute concentrations and deliveries were compared. Rootstocks of different dwarfing capacities maintained in micro-propagation were used to estimate and compare acropetal auxin transport; the velocity and intensity of PAT were determined using radiolabelled auxin. Sap osmolality and Ca+ + concentrations were reduced by passage through the M.9 graft union at very low flow rates. At transpirational flow rates, Ca++ and Mg++ concentrations were increased, and those of Na+ and NO3− decreased, by passage through the graft union. Deliveries of anions and cations from roots into shoots of M.9 composite trees were always similar or greater than those of MM.106 composite trees. Sap zeatin and zeatin riboside concentrations were reduced above the graft in both rootstocks. No evidence was found that a sub-optimal supply of essential mineral ions was involved in the dwarfing effect of M.9. Root- and shoot- specific deliveries of ABA in M.9 composite trees were significantly higher compared to MM.106 trees, and the greater import of ABA correlated temporarily with earlier shoot growth termination in M.9 composite trees. Intensity of PAT through micro-propagated stem tissue was lower in the dwarfing rootstock compared to more invigorating rootstocks.

Early shoot growth termination in Betula pendula is associated with the number of overwintering aphid eggs on boreal birches

Many autumn migrating and phloem-feeding insects, like aphids, use leaf reflectance to distinguish senescing foliage. They consume resources in autumn and lay eggs that hatch in spring when trees need phloem nutrients for developing leaves. The herbivores may thus drive the evolution of tree senescence and autumn leaf colours. In accordance with this, the yellowing birch leaves attract aphids (Euceraphis betulae) and the genotypic variation in the timing of autumn leaf colouration is associated with the abundance of oviparous wingless female aphids in a natural Betula pendula population. Currently, however, there are no published studies investigating the potential association of autumn senescence and the number of overwintering aphid eggs. We examined a local B. pendula population in 2001 and 2002 for genotypic differences in the timing of shoot growth termination and for the abundance of overwintering birch aphid eggs. There were heritable differences in the timing of shoot growth termination among B. pendula genotypes. The genotypes that terminated shoot growth early had higher aphid egg loads after a short but not after a long autumn. We suggest that this is because the egg laying period was cut off due to a rather sudden and substantial change in the temperature in the shorter autumn. We are the first to find genotypic differences associated with the overwintering offspring of autumn-migrating aphids on a widely distributed temperate broadleaved tree. As shoot growth termination directly precedes leaf senescence, autumn-migrating aphids may have an additional potential to influence indirectly but significantly the onset of autumn leaf senescence at an evolutionary scale.

Premature shoot growth termination allows nutrient loading of seedlings with an indeterminate growth strategy

Nutrient loading of nursery seedling stock of species with an indeterminate growth strategy is challenging and poorly understood. Here, we explore the use of two potential techniques for nutrient loading of trembling aspen (Populus tremuloides Michx.) seedlings: (1) exponential fertilization and (2) early shoot growth termination in order to divert assimilated nutrients and carbon to storage rather than to growth. In the first study, aspen seedlings were treated with either exponential or constant fertilization rates, both of which supplied the same amount of nutrients over the growing season. Exponential fertilization resulted in overall poor planting stock form (stunted seedling growth and weak root development) and produced only marginal improvements of nutrient status. As a result, the exponential fertilization regime studied cannot be recommended as a treatment for aspen seedlings. In the second study we treated seedlings with a 2 × 2 factorial combination of fertilization and shoot growth inhibitor (SGI) applications with the fertilizer treatments varying in terms of mid-season fertilizer concentrations. Seedlings with SGI application had much higher tissue nutrient and carbon reserve concentrations than seedlings without a SGI application. In addition, nutrient uptake appeared to be more efficient in SGI treated seedlings, which could potentially result in significant reductions of nutrient application rates during aspen seedling production in nurseries. Overall, early shoot growth termination using a SGI appears to be an effective technique to produce nutrient loaded aspen seedlings.

Partitioning of 13C-photosynthates from different current shoots neighboring with fruiting spur in later-maturing Japanese pear during the period of rapid fruit growth

To elucidate the fate of photosynthates from different current shoots and their influence on fruit growth and bud differentiation in neighboring spur complex during the period of rapid fruit growth in two late-maturing Japanese pear cultivars: ‘Atago’ and ‘Shinkou’ with contrasting fruit size, 13C labeling of single shoot was done to investigate of C-relations in fruit branches of eight shoot-combinations. The results showed that all of the current shoots investigated (bourse shoots of nonfruiting spur, bourse shoots of fruiting spur, extension shoot, nonfruiting spur, vegetative shoot, and water sprout) could export photosynthates to the neighboring fruit and buds. Water sprouts together with vegetative shoots, bourse shoots, and extension shoots are important source for fruit growth after shoot growth termination during the period of rapid fruit growth in production of late-maturing pears. The carbon transfer rate from the neighboring to the fruit bearing spur is depent (i) on the types of shoot which acts as C source, (ii) on the position of the fruiting spur and (iii) on the source-sink distance. Furthermore, the cultivar difference in carbon partitioning from different current shoot-combinations confirmed that the movement of photosynthates into the fruit was determined by sink strength of the fruit, and ‘Atago’ exhibited a greater relative sink strength of fruit than ‘Shinkou’. In addition, vegetative shoots are very important C sources for fruit growth in ‘Atago’ and the growth pattern of bourse shoot seriously affects C allocated to fruit in ‘Shinkou’.

Impact of elevated carbon dioxide concentration and temperature on bud burst and shoot growth of boreal Norway spruce

Effects of elevated temperature and atmospheric CO2 concentration ([CO2]) on spring phenology of mature field-grown Norway spruce (Picea abies (L.) Karst.) trees were followed for three years. Twelve whole-tree chambers (WTC) were installed around individual trees and used to expose the trees to a predicted future climate. The predicted climate scenario for the site, in the year 2100, was 700 micromol mol-1 [CO2], and an air temperature 3 degrees C higher in summer and 5 degrees C higher in winter, compared with current conditions. Four WTC treatments were imposed using combinations of ambient and elevated [CO2] and temperature. Control trees outside the WTCs were also studied. Bud development and shoot extension were monitored from early spring until the termination of elongation growth. Elevated air temperature hastened both bud development and the initiation and termination of shoot growth by two to three weeks in each study year. Elevated [CO2] had no significant effect on bud development patterns or the length of the shoot growth period. There was a good correlation between temperature sum (day degrees>or=0 degrees C) and shoot elongation, but a precise timing of bud burst could not be derived by using an accumulation of temperature sums.

Seasonal development of phloem in scots pine stems

The formation of phloem was studied for two years in stems of 50 to 60 year old trees of Scots pine (Pinus sylvestris L.) growing in nature. The development of phloem of the current year begins 10 to 20 days before the xylem formation and is completed with the termination of shoot growth in the end of June. Observations over the seasonal activity of cambium producing sieve-like cells of phloem and duration of their differentiation as compared to the xylem derivatives of cambium have shown that the maxima of formation of phloem and xylem cells could coincide or not coincide by season, while the activities of their differentiation were always at antiphase. The sieve-like cells of early phloem were separated from those of late phloem by a layer of tannin-containing cells, which are formed simultaneously with the formation of late xylem cells by the cambium. Seasonal dynamics of accumulation of starch grain in structural elements of the phloem is related to the xylem development. The content of metabolites in differentiating and mature phloem elements, in the cambium zone, and in the xylem cells growing in the radial direction depended on cell specificity, stage of their development, and type of forming wood, early or late, which differ in the cell wall parameters and, hence, requirement of assimilates. Significant differences were described between the content of low molecular weigh carbohydrates, amino acids, organic acids, and phenol compounds using two methods of calculation: per dry weight and per cell.

Indole 3-acetic acid concentration in the leading shoot and living stem bark of Scots pine: seasonal variation and effects of pruning.

Seasonal changes in the concentration of indole-3-acetic acid (IAA) in the leading shoot and in the live tissue external to the xylem (living bark) of 2-3 m tall Scots pine (Pinus sylvestris L.) trees were observed over a period of three years. Both the leading shoot and the living bark showed a consistent pattern of seasonal variation in IAA content, with maxima of about 150 and 350 ng g(-1) (fresh weight), respectively. The IAA concentration in both tissues increased in late June at the time of shoot growth termination, decreased from late August, and by October reached a low value, which was maintained throughout the winter. Excision of current year shoots on the upper branches decreased the annual stem diameter increment without affecting the concentration of IAA in the living bark. However, excising the leading shoot, or girdling the mainstem beneath the leading shoot, caused a substantial reduction in the IAA content of the living stem bark.

Stimulation of Lateral Bud Growth of Apple Trees by 6-Benzylamino Purine1

Abstract Orchard and greenhouse experiments were conducted to determine the influence of foliar applications of 6-benzylamino purine (BA) on branching of young apple trees. BA at 100 and 500 ppm, applied to actively growing shoots stimulated lateral bud growth on these shoots during the current season. The presence of fruit, termination of shoot growth, and the localization and non-persistence of BA reduced its effectiveness in breaking apical dominance. For optimum response to BA, multiple spray applications to actively growing shoots in a non-fruiting condition were required. Spray applications of BA failed to induce lateral bud growth on previous season’s wood.

Some effects of the photoperiod on the shoot growth of cherry seedlings

For cherry breeding it may be of importance to know the factors affecting the growth and development of cherry seedlings. Since it is known from the literature that the photoperiod is an important factor in the annual growth cycle in woody plants, experiments on the influence of the photoperiod were started in the phytotron of our Institute. The effect of 8 and 16-hr. photoperiods on the shoot growth of first- and second-year seedlings of Limburgse boskriek (P. avium L.) was studied at a constant temperature of 20°C. In one experiment the influence of a 24-hr. photoperiod in second-year seedlings was also studied. It was found that under the conditions of these experiments first- and second-year cherry seedlings respond differently to the photoperiod as regards termination of shoot growth. In first-year seedlings many of the plants under 8 and 16-hr. photoperiods terminated their growth at the same time. However, some of the plants under an 8-hr. photoperiod terminated growth much sooner, while a number of plants grown under a 16-hr. photoperiod terminated their growth considerably later. In second-year seedlings growth was terminated at about the same time under 8, 16 and 24-hr. photoperiods.