Mature Scions Research Articles

Effect of tree age, scion source and grafting period on the grafting success of cashew nut (Anacardium occidentale L.)

Cashew (Anacardium occidentale L.) can be propagated by seed or vegetative propagation. Grafting is the best method for large-scale asexual propagation of cashew. An assessment of grafting success of cashew nut was conducted at Chikwawa Estate nursery where graft-take was compared for scions obtained from different populations of different ages and then grafted from the month of August to October 2008. Mature and immature scions were collected from forty cashew accessions of age 12 and 20 years in Liwonde, Nkope, Kaputu and Chikwawa populations. Results show that scion source and tree age had no effect on grafting success. However, there were significant differences (p ≤ 0.05) for scion type. Immature scions performed better in August while mature scions did well in October. The differences are attributed to differences in temperature in the two months that further affect rate of healing of graft unions. There were significant differences (p ≤ 0.05) for graft take of mature scions as compared to immature scions with 57.5 and 72.5% in August and October respectively. There were no correlations between cashew tree age and scion type on the grafting success suggesting that cashew scions could be collected from trees of different ages to be used for grafting. Key words: Anacardium, grafting, graft-take, season, scion type.

IN VIVO SERIAL MICROGRAFTING OF CASTANEA SATIVA IN SHORT CYCLES

Mature material of Castanea sativa has been serially grafted on 4-week-old chestnut seedlings in growth chamber conditions. The mature scions were: (a) nodes from shoots emerged from branch segments (from the crown of the tree) forced in a growth chamber (clone 'EPS-CR'), and (b) nodes from in vitro cultures of two selected clones (clones 'Loura' and 'Parede'). The graft technique was a miniaturized simple cleft graft. Once the grafts had taken and the scions had elongated and developed new buds (40-60 days after grafting), new scions/explants were obtained and either re-grafted (clones 'Loura', 'Parede' and 'EPS-CR') or established in vitro (clone 'EPS-CR'). Three grafting cycles were completed. The graft-take has ranged from about 20% in clone 'EPS-CR' to 50-90% in clones 'Loura' and 'Parede'. In clones 'Loura' and 'parade', grafted scions treated with GA 3 can supply, every 40-60 days, about 6 new scions per successful graft. In clone 'EPS-CR', in vitro reactivity, multiplication rate and rooting percentage of grafted and ungrafted material was compared, and no significant differences have been observed by now. This technique could be useful for different purposes, i.e., as a rapid propagation system to produce grafted plants, as a method to increase explant availability for micropropagation or as a method of rejuvenation of mature material.

Variations in DNA methylation, acetylated histone H4, and methylated histone H3 during Pinus radiata needle maturation in relation to the loss of in vitro organogenic capability

Needle differentiation is a very complex process associated with the formation of a mature photosynthetic organ. From meristem differentiation to leaf maturation, gene control must play an important role switching required genes on and off to define tissue functions, with the epigenetic code being one of the main regulation mechanisms. In this work, we examined the connections between the variation in the levels of some epigenetic players (DNA methylation, acetylated histone H4 and histone H3 methylation at Lys 4 and Lys 9) at work during needle maturation. Our results indicate that needle maturation, which is associated with a decrease in organogenic capability, is related to an increase in heterochromatin-related epigenetic markers (high DNA methylation and low acetylated histone H4 levels, and the presence of histone H3 methylated at lys 9). Immunohistochemical analyses also showed that the DNA methylation of palisade parenchyma cell layers during the transition from immature to mature scions is associated with the loss of the capacity to induce adventitious organs.

Nuclear and cytoplasmic changes associated with maturation in the vascular cambium of Larix laricina.

We studied the effects of apical maturation on the vascular cambium of juvenile and mature scions of Larix laricina (Du Roi) K. Koch that had been grafted on seedling rootstocks. Comparisons between the juvenile and mature cambium in nuclear genome size, nuclear shape, DNA concentration, number and volume of nucleoli per nucleus, and concentration of extranuclear RNAs, proteins and insoluble carbohydrates were conducted on four occasions during the annual cycle of cambial activity and dormancy. All investigated variables exhibited strong annual oscillations, whereas differences between the two maturation stages were less prominent. Many of the differences between the two phases could be explained by delayed spring reactivation and accelerated onset of dormancy in the mature cambium compared with the juvenile cambium. At the time of reactivation and during activity, the mature cambium exhibited lower genome size, lower DNA concentration, fewer nucleoli per nucleus and a higher extranuclear concentration of insoluble carbohydrates than the juvenile cambium. The dormant mature cambium contained more extranuclear RNAs than the dormant juvenile cambium. The observed differences provide circumstantial evidence of changes in chromatin organization or functioning, or both, during maturation.

Ozone effects on grafted mature and juvenile red spruce: photosynthesis, stomatal conductance, and chlorophyll concentration

Red spruce (Picearubens Sarg.) was grown as grafted mature and juvenile scions in open-top chambers and exposed to charcoal-filtered air, nonfiltered air, and nonfiltered air with ozone additions of either 75 or 150 ppb above ambient to determine if tissue age affects the species response to oxidant pollution as measured by photosynthesis, stomatal conductance, and chlorophyll concentration. After 18 weeks of exposure to ozone of concentrations as high as 170 ppb (nonfiltered air + 150 ppb ozone) in an 8-h period, net photosynthesis of grafted red spruce was reduced by ozone. Significant reductions were not observed until September 1988. Mature and juvenile scions grown in nonfiltered air + 150 ppb ozone showed 29 and 40% reductions, respectively, in mean seasonal net photosynthesis (mg CO2•g dry wt.−1•h−1) compared with those plants grown in nonfiltered air. Scion age had a significant effect on net photosynthesis and stomatal conductance. Net photosynthesis (mg CO2•g dry wt.−1•h−1) and stomatal conductance were 38 and 47% higher, respectively, in juvenile than in mature scions. Chlorophyll a and total chlorophyll concentration of juvenile scion needles were significantly reduced 19 and 24%, respectively, when grown in nonfiltered air + 150 ppb ozone compared with that grown in charcoal-filtered air (p < 0.01). Mature scions had significantly more chlorophyll a than juvenile scions in October 1988. Current-year needles collected from mature scions had significantly greater mass, length, one-sided projected surface area, width, and thickness than juvenile scions. Mature scions had significantly lower needle numbers per centimetre branch than did juvenile scions. No differences in specific leaf weight were observed. Mature scions had less ozone uptake than did juvenile scions.

No general effect of ozone on foliar nutrient concentrations in mature scions of grafted Picea abies trees.

The effect of ozone (< 10, 200, or 400 microg m(-3)), on foliar nutrient concentrations of Picea abies were determined by fumigating potted grafts from mature trees (> 55 and 125 years), representing six clones, in open-top chambers at two locations in Norway. The concentration of nutrients in needles of grafted plants were significantly affected by clone and location. Generally, the concentrations of nutrients were not affected by ozone, but a significant increase in the concentrations of potassium and iron in two of the clones were found. These two clones were the only ones injured (yellow needles) by the fumigation.

Cone Production by Rooted Cuttings, Grafts, and Seedlings of Western Larch

Abstract Cone production in 1991 was compared among rooted cuttings from juvenile trees, grafts from mature scions, and seedlings planted in a common garden in Plains, MT, in 1981 and 1983. The differences among tree types were statistically significant for the mean number of cones per tree, but were not significant for the percent of trees producing cones. A projection of cone production per 1,000 trees showed that the grafts would produce nearly twice the number of cones as the seedlings and more than five times the number of cones as the rooted cuttings under the same conditions. West. J. Appl. For. 7(4):108-109.

Ozone effects on the growth of grafted mature and juvenile red spruce

Grafted juvenile and mature scions of red spruce (Picearubens Sarg.) were grown in open-top chambers at a low-elevation site in central Maine to determine if developmental age of tissue affects response to oxidant pollution. After 18 weeks of ozone exposure, grafted red spruce showed little or no growth response to ozone. No significant ozone effect on biomass production was measured, although there were significant differences between juvenile and mature scions. At the final harvest, juvenile scion stem, stem needles, branches, branch needles, and roots had 60, 18, 74, 73, and 35% more dry weight, respectively, than mature scions. Despite the observed differences in growth and biomass production, the two graft types did not differ in their responses to ozone, suggesting that tissue age may not be a factor in ozone-tolerant woody species such as red spruce. It does not preclude the importance of assessing the influence of age on other woody species' response to air pollution. This type of information is critical for extrapolation of seedling data to field conditions with mature trees.

Maturation in Larch

The time course of maturation in eastern larch (Larix laricina [Du Roi] K. Koch) was examined by grafting scions from trees of different ages onto 2-year-old root stock and following scion development for several years. Height, diameter, foliar chlorophyll content, and rooting ability of scion-derived cuttings all varied linearly as a function of log(10) age. Chlorophyll content (milligrams per gram of dry weight) increased while height, diameter, and ability to root decreased with age (P < 0.01). The tendency toward orthotropic growth and branch formation per centimeter of main stem decreased abruptly between age 1 and 5 years (P < 0.01). Total chlorophyll content of both long and short shoot foliage increased by 30 to 50% with increasing age, but the chlorophyll a/b ratio did not change. Also, juvenile long shoot needles were significantly longer than mature (P < 0.01). Surprisingly, the juvenile scions produced more total strobili over two successive years, but the mature scions produced a significantly higher proportion of male strobili (P < 0.001 year 1; P < 0.02 year 2). The age-related changes in foliar traits were not associated with changes in DNA methylation between juvenile and mature scions. Using HPLC, we found that 20% of foliar DNA cytosine residues were methylated in both scion types.

In vitro propagation of mature trees of Alnus incana (L.) Moench.

Mature trees of European grey alder (Alnus incana) were micropropagated on a modified MS medium containing 2.5 μM BA, 6.2 mM (500 mg l-1) NH4NO3 and 1.5% glucose. Prior to in vitro culture, mature scions were multiplied through grafting and cutting techniques. Shoot tips from cuttings were established in vitro. After six months of culture, shoots were rooted either in vitro or in vivo and plantlets were transferred to greenhouse conditions.

The effect of bark phenols upon mountain hare barking of winter‐dormant Scots pine

Due to high numbers of mountain hares in recent winters in northern Finland the barking of winter dormant Scots pines was widespread. The hares fed selectively upon upper crown bark of grafted pines, nitrogen fertilized trees and trees in poor condition. Bark of preferred upper crown branches and physiologically mature scions contained less total phenols than lower parts. However, there were no differences between total phenols concentrations of graft bark preferred by hares and nearby unbarked juvenile phase Scots pine. Neither decrease in resistance after nitrogen fertilization n‐ or stress was correlated with bark total phenolic concentration. Thus, total phenolic concentration is not a reliable predictor of the susceptibility of Scots pine to winter barking by the mountain hare.

Rate, timing, and mode of gibberellin application for female strobilus production by grafted loblolly pine

Gibberellin A4, gibberellin A7, and their mixture (60:40, GA4:GA7) were approximately equally effective in promoting female strobilus production on 3-year-old grafted mature scions of loblolly pine (Pinustaeda L.). Gibberellin A3 was ineffective. The female flowering response to GA4/7 was proportional to the log of its concentration, but no significant effect on male flowering was observed. Topical application from June through September was the most effective mode of application. Application for shorter intervals during this period resulted in proportionately less flowering. GA was equally effective prior to and following female bud initiation, but most effective during both.

Promotion of flowering in the Pinaceae by gibberellins

AbstractSignificant female flowering of 6‐ to 11‐year‐old seedlings and grafted ramets of sexually mature scions of lodgepole pine (Pinus contorta Dougl.) was promoted by both topical and spray applications of a gibberellin (GA) A4/7 mixture (1.6 to c. 5 mg per plant in total) during that period (June to September) when sexual differentiation of lateral primordia would be expected to take place. Girdling was used in most experiments to enhance the GA4/7 effect, as was the auxin, naphthaleneacetic acid (NAA). Average frequency of flowering branches on treated plants over all experiments ranged from 27 to 59% (control ranged from 0 to 36%) and average number of female strobili was increased from 2‐ to 6‐fold by growth regulator treatment, relative to controls. Within an experiment, clonal or family frequency of flowering for treated plants ranged from 11 to 67% (controls were 0 to 28%), and number of female strobili was increased from 2‐ to 14‐fold by growth regulator treatment, relative to controls. Movement of the flowering stimulus from the point of application was apparent in several experiments, the response in adjacent branches being correlated positively with increasing dosage of GA4/7. Significant male flowering occurred only in one experiment, girdling and GA4/7 treatment being promotive factors. The use of spray applications of GA4/7+ NAA is warranted to induce early and enhanced flowering in lodgepole pine seedlings and vegetative propagules for genetic improvement programs.

Promotion of cone and seed production on Sitka spruce by gibberellin application

SUMMARYGibberellin mixtures were applied to large, mature scions of Sitka spruce, growing in the open at Wauchope Tree Bank in 1975, 1976 and 1977. Large increases in coning and seed production, and in the numbers of clones producing seed, occurred in the year after treatment. Cone and seed yields varied with the timing and concentration of hormone treatment, and were greatest when applications were made in the top two branch whorls on the tree. Clonal differences in seed production were observed among gibberellin‐treated branches. Seed quality, judged by seed weight and percentage germination, appeared normal. Promotion of male strobili was greater in lower branch whorls than in the top branch whorl on the tree.Ways in which these findings can be applied in breeding and seed production are discussed.

Promotion of Flowering on Mature Picea sitchensis by Gibberellin and Environmental Treatments. The Influence of Timing and Hormonal Concentration

AbstractMale and female flowering were significantly promoted by gibberellin A4/7+ A3 mixtures applied beneath bark flaps on branches of 11‐year‐grafted mature scions of Picea sitchensis (Bong.) Carr. growing in the open in Scotland; 4 mg/ml gave more flowering than higher or lower concentrations of gibberellins and application in June was more effective than in July.Gibberellins also increased male flowering on mature scions when applied directly to the buds in a polythene house. A gibberellin A4/7+ A3 mixture produced greater numbers of strobili when applied to 2‐year‐grafted plants in May and June than when applied in July and August. Flowering of 5‐year‐grafted plants increased with increasing concentrations of a gibberellin A4/7+ A9 mixture up to 19.7 mg/ml above which flowering decreased.Modifying the environment by keeping in a polythene house enhanced the combined male and female flowering of 5‐year‐grafted mature scions above the amount on control plants outside, the effect being more marked in June and July than in August and September. Larger numbers of gibberellin applications or longer total lengths of time in the polythene house gave significantly greater amounts of combined male and female strobili.

Studies of Growth and Flowering in Picea sitchensis (Bong.) Carr. 1. Effects of Growth Regulator Applications to Mature Scions on Seedling Rootstocks

Studies of Growth and Flowering in Picea sitchensis (Bong.) Carr. 1. Effects of Growth Regulator Applications to Mature Scions on Seedling Rootstocks