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a Severe case of needle discoloration affecting the upper crown of a lodgepole pine ramet shortly after GA4/7 stem injections; b needle discoloration spreading along entire branches starting at the tips and including multiple years of needles
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Seed orchards play a critical role in reforestation, but often struggle to consistently produce enough seed. A mixture of the less polar gibberellins, GA4 and GA7, has been shown to promote flowering in Pinaceae species, but the responses vary significantly based on species, genotype and provenance, application method, timing and dosage. Previous s...
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A critical issue in effective post-fire regeneration and re-establishment of a burnt forest is the stage concerning the burned stands. When stands are mature and produce seeds, the regenera-tion can theoretically be achieved, while in the case of immature stands, they may not be able to produce enough quantities of germinable seeds that can secure...
Citations
... Both environmental and genetic control of cone formation are mediated through hormonal signaling within trees [4]. In particular, gibberellic acid (GA) levels are a primary driver of coning in conifers and seed orchard managers often apply GA to induce coning [5,6]. For example, trunk-injection of GA4/7 combined with fertilizer, girdling, and tenting resulted in a 30-fold increase in cone production in Pacific silver fir (Abies amabilis [Douglas ex Loudon] Douglas ex Forbes) [7]. ...
Early cone formation is a consistent issue in Fraser fir Christmas tree plantations in the eastern United States. Growers must remove cones by hand, resulting in significant labor costs, as cones degrade the aesthetic value of Christmas trees. In this study, we conducted two series of experiments in collaboration with several Christmas tree farms to determine the effectiveness of applying plant growth regulators (PGRs), specifically GA-inhibitors, in reducing cone formation and shoot growth in Fraser fir. In the first experiments we investigated the effectiveness of paclobutrazol, applied as a soil injection or as a foliar spray in reducing cone formation. The highest rate of soil application (300 mL of paclobutrazol per tree) reduced cumulative coning by approximately 38%. Leader growth control of soil applied paclobutrazol increased with application rate. In the second set of experiments, we compared four GA-inhibitors (paclobutrazol, chlormequat chloride, uniconazole-p, daminozide) applied as foliar sprays on coning and leader growth. Overall, paclobutrazol was the most effective compound for reducing coning and shoot growth. The results confirm earlier findings that application of GA-inhibitors can reduce, but not eliminate, coning. Likewise, PGR application can reduce shoot growth and possibly increase tree density but will not eliminate the need for shearing.
... Thus, in conifers, GA promotes the transition to the adult phase. Exogenous GA application can promote early transition from juvenile to adult by inducing the reproductive phase and cone production in young conifer trees (Pharis et al. 1980(Pharis et al. , 1987Bockstette and Thomas 2019). ...
Woody perennials usually have two distinct growth phases: juvenile and adult. The transition from juvenile wood (core wood) to adult wood (outer wood), which occurs gradually during tree development, is regulated by hormonal signals and their gradients along the plant axis, with opposing mechanisms in conifers versus angiosperms. Gibberellin is a key controlling signal in juvenile-adult transition. GA promotes the transition from the juvenile to the adult stage in young conifer trees by inducing the reproductive phase and cone production; while GA can delay the reproductive phase in angiosperms and may promote rejuvenation of adult woody angiosperms. Root signals arriving to the shoot apical meristem (SAM) delay the transition from the juvenile to the adult phase. Grafting adult branches on young juvenile rootstocks can promote rejuvenation of both buds and cambium in the scion (adult branch) that start to produce typical juvenile features. Since the cambium is influenced and produces wood in response to the hormonal signals it receives, the vague term cambial age (i.e., young cambia produce juvenile wood and old cambia produce mature wood) should be avoided. The nature of the produced wood does not depend on the chronological age of the vascular cambium, but on the hormonal signals and carbohydrates supply that it received; with the appropriate hormonal stimulation, an adult cambium can start to produce juvenile wood.
This study has been supported by the grants the Russian Science Foundation, RSF 23-26-00228, https://rscf.ru/project/23-26-00228/, https://elibrary.ru/jtyxux.
The seeds germination of the Scots pine (Pinus sylvestris L.) is an important stage of the tree's life cycle and determines the subsequent productivity and survival, ultimately affecting the composition of the plant community. Germination is related to various biological characteristics of seeds, including individual seed mass. The amount of endosperm nutrients contained in sound seeds can determine the energy available for germination. Experimental evidence of the influence of individual seed mass on germination is still quite small. To test the technology of planting material production with a closed root system, taking into account the individual spectrometric and morphometric features of the Negorelskaya variety for each varietal seed of the Scots pine (P. sylvestris L.), three random sets of 400 de-winged seeds (N = 1200) were sown manually in 40-mesh SideSlit containers of an automated forest nursery. To test the hypothesis about the influence of the individual seed mass of the Scots pine (P. sylvestris L.) varieties "Negorelskaya" on the indicators of its germination in SideSlit containers on the 30th day, a single-factor analysis of variance was used with a check of uniformity according to the Levene's criterion and a posteriori LSD test of averages. The individual mass of the sown seeds varied from 1.0 to 13.3 mg (m ± SD | 60.1 ± 17.5 mg). The average values of the germination index of the seeds of Negorelskaya variety Scots pine (P. sylvestris L.) on day 30 in the volume of 6,8,12,16,18,26 SideSlit containers statistically (Levene's criterion 6.35, p = 1.98e-22; ANOVA F-criterion 1.291, p = 0.0139; a posteriori criterion LSD p < 0.05) differ from the indicator in 2,7,10,11,13,19,22,24,26,27,29 containers. The average values of the individual mass of 942 seeds germinated on the 30th day in the cells of SideSlit containers of the automated forest nursery statistically (Levene's criterion 11.317; p = 0.000792; ANOVA F-criterion 12.098; p = 0.000523) differ from the average values of the individual weight of the ungrown 258 seeds of the Negorelskaya variety Scots pine (P. sylvestris L.). In the future, this seed germination on day 50 in SideSlit containers and comprehensive quality indicators of the seedlings, including DQI and RQI, will be studied.
Flowering, the beginning of the reproductive growth, is a significant stage in the growth and development of plants. Conifers are economically and ecologically important, characterized by straight trunks and a good wood quality and, thus, conifer plantations are widely distributed around the world. In addition, conifer species have a good tolerance to biotic and abiotic stress, and a stronger survival ability. Seeds of some conifer species, such as Pinus koraiensis, are rich in vitamins, amino acids, mineral elements and other nutrients, which are used for food and medicine. Although conifers are the largest (giant sequoia) and oldest living plants (bristlecone pine), their growth cycle is relatively long, and the seed yield is unstable. In the present work, we reviewed selected literature and provide a comprehensive overview on the most influential factors and on the methods and techniques that can be adopted in order to improve flowering and seed production in conifers species. The review revealed that flowering and seed yields in conifers are affected by a variety of factors, such as pollen, temperature, light, water availability, nutrients, etc., and a number of management techniques, including topping off, pruning, fertilization, hormone treatment, supplementary pollination, etc. has been developed for improving cone yields. Furthermore, several flowering-related genes (FT, Flowering locus T and MADS-box, MCMI, AGAMOUS, DEFICIENCES and SRF) that play a crucial role in flowering in coniferous trees were identified. The results of this study can be useful for forest managers and for enhancing seed yields in conifer plantations for commercial use.
The major signaling molecules that regulate vascular differentiation and plant development are the plant hormones, also called phytohormones. The word hormone is derived from Greek, meaning to set in motion, excite, and stimulate. Plant hormones regulate gene expression, cellular activity, cell and tissue polarity, and growth and differentiation of tissues, organs, and the whole plant. The hormones can be produced in any living plant cell at extremely low concentrations. They may act locally or at a distance from the producing cells. The primary phytohormones that regulate vascular differentiation, namely, auxin, cytokinin, gibberellin, and ethylene, are discussed, with additional hormonal signals needed for understanding vascular differentiation in plants.
