scholarly journals Fruit Load Limits Root Growth, Summer Vegetative Shoot Development, and Flowering in Alternate-bearing ‘Nadorcott’ Mandarin Trees

2018 ◽  
Vol 143 (3) ◽  
pp. 213-225 ◽  
Author(s):  
Ockert P.J. Stander ◽  
Graham H. Barry ◽  
Paul J.R. Cronjé
Keyword(s):  
Root Growth ◽  
Shoot Development ◽  
Sugar Concentration ◽  
Tree Level ◽  
Alternate Bearing ◽  
Vegetative Shoot ◽  
Carbohydrate Concentration ◽  
Growth Activity ◽  
Return Bloom ◽  
Fruit Load

The objectives of this study were to improve the understanding of the mechanism of alternate bearing and the role of carbohydrates in ‘Nadorcott’ mandarin (Citrus reticulata) trees. Selected phenological responses were measured in natural heavy- (“on”) and low-fruiting (“off”) ‘Nadorcott’ mandarin trees grown under commercial South African production conditions. The relationships with seasonal leaf and root carbohydrate concentrations were evaluated at the shoot-, branch- and tree level over two seasons. Fruit load [R2 = (−)0.80 and R2 = (−)0.73 in seasons 1 and 2, respectively; (P < 0.01)] and the number of newly developed vegetative shoots [R2 = 0.81 and R2 = 0.78 in seasons 1 and 2, respectively; (P < 0.01)] were the most important determinants of return bloom. Sprouting of a higher number of new vegetative shoots from “off” trees compared with “on” trees (“off” = 863 and 1439 vs. “on” = 306 and 766) was not related to leaf carbohydrate concentration. Root sugar concentration peaked during full bloom and higher root growth activity was observed before a higher number of new vegetative shoots developing in “off” trees during summer. The root sugar concentration early in the season was ≈3-fold lower, and root and shoot growth were absent, or lower in “on” trees compared with “off” trees. These results concur with previous research and confirm that fruit load in “on” trees inhibits summer vegetative shoot development, which manifests in poor flowering and an “off” year. This study shows that fruit are the major carbohydrate sink and probably disturb the balance between vegetative shoot development and root growth by limiting carbohydrate allocation to roots.

scholarly journals The Significance of Macronutrients in Alternate Bearing ‘Nadorcott’ Mandarin Trees

HortScience ◽  
2018 ◽  
Vol 53 (11) ◽  
pp. 1600-1609 ◽  
Author(s):  
Ockert P.J. Stander ◽  
Graham H. Barry ◽  
Paul J.R. Cronjé
Keyword(s):  
Treatment Effects ◽  
Foliar Spray ◽  
Shoot Development ◽  
Citrus Reticulata ◽  
Alternate Bearing ◽  
Vegetative Shoot ◽  
Current Season ◽  
Standard Practice ◽  
Main Determinants ◽  
Fruit Load

The significance of macronutrients nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) in leaves was studied in relation with their possible roles in alternate bearing of ‘Nadorcott’ mandarin (Citrus reticulata) trees over a period of three seasons. Fruit load (“on,” a heavy fruit load, vs. “off,” a light fruit load) affected the leaf macronutrient concentrations, and the amount of macronutrients removed through the harvest of fruit, i.e., the crop removal factor (g·kg−1), was consistent in both seasons. The crop removal factors were higher for each macronutrient in “off” trees—harvest of 1 kg fruit removed ≈2.3 g·kg−1 N, 0.3 g·kg−1 P, 3.1 g·kg−1 K, 1.0 g·kg−1 Ca, and 0.4 g·kg−1 Mg, compared with 1.3 g·kg−1 N, 0.2 g·kg−1 P, 1.7 g·kg−1 K, 0.6 g·kg−1 Ca, and 0.2 g·kg−1 Mg in “on” trees. Fruit load per tree (kg/tree) of 84, 110, and 52 kg/tree in “on” trees, however, removed ≈217 g/tree N, 28 g/tree P, 296 g/tree K, 100 g/tree Ca, and 35 g/tree Mg, which was 1.5–6 times more than that of fruit loads of 14, 71, and 16 kg/tree in “off” trees. In “off” trees, N, P, and K, and in “on” trees, Ca accumulated in leaves to between 20% and 30% higher concentrations in season 1, but the higher macronutrient status did not manifest in or consistently correlate with intensity of summer vegetative shoot development in the current season, or intensity of flowering in the next season, the two main determinants of fruit load in ‘Nadorcott’ mandarin. Apart from some anomalies, the concentrations of macronutrients in leaves were unaffected by de-fruiting and foliar spray applications of N and K to “on” trees, and showed no consistent relationship with treatment effects on parameters of vegetative shoot development and flowering. Leaf macronutrients in alternate bearing ‘Nadorcott’ mandarin trees, fertilized according to grower standard practice, are not related to differences in flowering and vegetative shoot development, and appear to be a consequence of fruit load and not a determinant thereof.

scholarly journals Mechanism and Underlying Physiology Perpetuating Alternate Bearing in Citrus

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1117C-1117
Author(s):  
Johannes S. Verreynne ◽  
Carol J. Lovatt
Keyword(s):  
Phase Transition ◽  
Shoot Growth ◽  
Indoleacetic Acid ◽  
Alternate Bearing ◽  
Vegetative Shoot ◽  
Fruit Removal ◽  
Inflorescence Development ◽  
Shoot Initiation ◽  
Shoot Production ◽  
Return Bloom

Alternate-bearing trees produce a heavy on-crop followed by a light off-crop. Whereas climatic events initiate alternate bearing, it is perpetuated by endogenous tree factors. For citrus, the mechanism and underlying physiology by which fruit influence floral intensity the next spring was unresolved. To determine whether reduced return bloom of on-crop trees was due to inhibition of vegetative shoot production and, thus, a lack of “wood” on which to bear next spring's inflorescences or, alternatively, to inhibition of phase transition and inflorescence development on an adequate number of vegetative shoots, fruit were removed from individual shoots monthly or from entire on-crop `Pixie' mandarin trees during periods critical to shoot initiation (summer) and phase transition (winter). Fruit removal provided clear evidence that the on-crop exerted a significant effect on return bloom during the summer by reducing summer–fall shoot growth and, hence, the number of flowers borne on these shoots as well as on old wood of fruit-bearing shoots. The on-crop had less effect in winter on phase transition and return bloom. Buds collected during the summer from on-crop `Pixie' mandarin trees were characterized by high indoleacetic acid and low isopentenyladenosine concentrations compared to buds from off-crop trees. The starch level of the buds was not affected. No differences in hormone concentrations were detected for buds collected during winter from on- and off-crop trees, but buds of on-crop trees had less starch. The results demonstrate that the on-crop reduces return bloom predominantly by inhibiting summer-fall vegetative shoot growth by a mechanism similar to apical dominance, not a lack of available carbohydrate.

scholarly journals Vegetative and Reproductive Response to Fruit Load in Two Jojoba (Simmondsia chinensis) Cultivars

Agronomy ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 889
Author(s):  
Aviad Perry ◽  
Noemi Tel-Zur ◽  
Arnon Dag
Keyword(s):  
Vegetative Growth ◽  
Accumulation Rate ◽  
Dry Weight ◽  
High Yield ◽  
Lower Amount ◽  
Simmondsia Chinensis ◽  
Alternate Bearing ◽  
Fruit Removal ◽  
Growing Period ◽  
Fruit Load

Jojoba (Simmondsia chinensis) is a wax crop cultivated mainly in arid and semi-arid regions. This crop has been described as an alternate-bearing plant, meaning that it has a high-yield year (“on-year”) followed by a low-yield year (“off-year”). We investigated the effect of fruit load on jojoba’s vegetative and reproductive development. For two consecutive years, we experimented with two high-yielding cultivars—Benzioni and Hazerim—which had opposite fruit loads, i.e., one was under an on-year load, while the other was under an off-year load simultaneously. We found that removing the developing fruit from the shoot during an off-year promotes further vegetative growth in the same year, whereas in an on-year, this action has no effect. Moreover, after fruit removal in an on-year, there was a delay in vegetative growth renewal in the consecutive year, suggesting that the beginning of the growing period is dependent on the previous year’s yield load. We found that seed development in the 2018 season started a month earlier than in the 2017 season in both cultivars, regardless of fruit load. This early development was associated with higher wax content in the seeds. Hence, the wax accumulation rate, as a percentage of dry weight, was affected by year and not by fruit load. However, on-year seeds stopped growing earlier than off-year seeds, resulting in smaller seeds and an overall lower amount of wax per seed.

scholarly journals The role of small RNAs in vegetative shoot development

2016 ◽  
Vol 29 ◽  
pp. 64-72 ◽  
Author(s):  
Jim P Fouracre ◽  
R Scott Poethig
Keyword(s):  
Small Rnas ◽  
Shoot Development ◽  
Vegetative Shoot

Effect of dietary sugars on tissue lipid and carbohydrate in developing honeybee larvae

1973 ◽  
Vol 51 (10) ◽  
pp. 1101-1108 ◽  
Author(s):  
W. Tsao
Keyword(s):  
Fat Body ◽  
Sugar Concentration ◽  
Tissue Lipid ◽  
Lipid Concentration ◽  
Natural Diet ◽  
Carbohydrate Concentration ◽  
Dietary Sugar ◽  
High Level ◽  
Dietary Sugars ◽  
Queen Larvae

Changing the sugar concentration in the diet of laboratory-reared honeybee larvae to simulate that of the natural diet for worker larvae induced sugar patterns similar to those found in natural worker larval haemolymph but not in the fat body. Feeding a low-sugar-level diet to larvae in the incubator showed changes in haemolymph sugar concentration similar to those found in natural worker larvae. This indicates that the changes in sugar concentrations around the third and the fourth molts are not the consequence of the changes of the dietary-sugar level but are regulated by an endogenous system. Addition of sugar to the early larval diet in the incubator showed changes in sugar concentration resembling those found in natural queen larvae. This indicates that the high level of sugar in the early diet is a factor inducing the development of the endogenous system in queen larvae. High sugar level in the early diet decreased tissue carbohydrate concentration but increased tissue lipid concentration which may be essential for the maturation of the reproductive system in queen larvae.

scholarly journals TIME OF FRUIT REMOVAL INFLUENCES RETURN BLOOM IN PECAN

HortScience ◽  
1990 ◽  
Vol 25 (9) ◽  
pp. 1128a-1128
Author(s):  
William Reid
Keyword(s):  
Alternate Bearing ◽  
Carya Illinoensis ◽  
Fruit Removal ◽  
Seed Crop ◽  
Stage 4 ◽  
Return Bloom ◽  
Water Stage ◽  
Dough Stage ◽  
Block Experiment

Pecan trees, Carya illinoensis, often exhibit a strong alternate bearing pattern. The presence of a heavy seed crop inhibits terminals from fruiting the following season. This study was developed to discover at what point in the development of the pecan fruit does this inhibition take place. Six nut removal times were evaluated: (1) after pollination but before fertilization, (2) one-half ovule expansion, (3) full ovule expansion or water stage, (4) dough stage, (5) 3 weeks after the initiation of the dough stage, and (6) no fruit removal until harvest. The cultivar `Mohawk' was used for this randomized block experiment.Return bloom was significantly enhanced by the removal of fruit prior to the initiation of kernel filling (dough stage). Less than 10% of terminals that supported pecans through the dough stage were able to produce distillate flowers the following year. Twig mortality was significantly higher for terminals that completed kernel filling. These results indicate that nut thinning prior to the water stage may reduce the alternate bearing tendency in pecan.

scholarly journals Correlations of Crop Load and Return Bloom with Root and Shoot Concentrations of Potassium, Nitrogen, and Nonstructural Carbohydrates in Pecan

2007 ◽  
Vol 132 (1) ◽  
pp. 44-51 ◽  
Author(s):  
Michael W. Smith ◽  
Charles T. Rohla ◽  
Niels O. Maness
Keyword(s):  
Growth Regulator ◽  
Current Theory ◽  
Nonstructural Carbohydrates ◽  
Alternate Bearing ◽  
Crop Load ◽  
Current Season ◽  
Flower Production ◽  
Previous Season ◽  
Second Growth ◽  
Return Bloom

The current theory of pecan [Carya illinoinensis (Wangenh.) C. Koch] alternate bearing is the “growth regulator–carbohydrate theory” in which flowering is first controlled by growth regulators produced by fruit and leaves, and then by the size of the carbohydrate pool near budbreak. Lack of nitrogen (N) reserves has also been proposed to be limiting after large crops, thus reducing return bloom. Annual production was determined for 12 individual trees for 3 years. Return bloom was monitored on four previous-season shoot types: 1) vegetative shoots, 2) bearing terminal shoots without a second growth flush, 3) bearing lateral shoots without a second growth flush, and 4) bearing shoots that were primarily in the terminal position with a second growth flush. Nonstructural carbohydrates, organically bound N, and potassium (K) concentrations were determined in roots and shoots. Regression analysis was used to determine the effect of yield on subsequent nonstructural carbohydrates, N, and K in the roots and shoots, and their postyield concentrations on subsequent flowering. Alternate bearing was evident because there were reductions of 18%, 16%, and 18% in the percentage of current season shoots flowering for every 10 kg/tree production increase in the previous season's yield in 2002, 2003, and 2004 respectively. Flower production in 2002 decreased by 2.6 flowers/1-year-old branch and 1.6 flowers/1-year-old branch in 2003 for each 10 kg/tree increase in production. The third year of the study, neither previous season shoot type nor yield affected subsequent flower production. The previous year's shoot type did not affect the percentage of current season shoots flowering; however, the previous year's shoots that had a second growth flush produced more flowers the following year than the other shoot types. Results suggested that crop load was not related to nonstructural carbohydrates, N, or K in the roots and shoots during January in these well-managed trees. Stored nonstructural carbohydrates, N, and K were also not related to return bloom. These data suggest that the current “growth regulator–carbohydrate theory” may not be valid in these well-managed trees. Nonstructural carbohydrates, K, and organically bound N do not appear to be critical factors regulating flowering.

Sign in / Sign up

Export Citation Format

Share Document