Breaking dormancy in deciduous fruit trees

Deciduous species are distinguished from other species by their dormancy period in winter. In practical terms, we can observe that in late autumn, trees begin to show yellow leaves, which fall, leaving the tree completely bare for the winter.
Dormancy is therefore presented as a physiological reaction of self-protection for meristems (growth structure for the new crop cycle), located inside the buds.

Several authors have suggested that dormancy occurs in response to a decline in day length toward the end of summer and a decline in temperature toward the end of autumn. This suggests that the plant may respond to environmental cues that promote the accumulation of reserves to protect itself from the winter cold. COLD AND HEAT REQUIREMENTS. In general, it is suggested that there are 3 types of dormancy:

• Paradormancy: Dependent on intrinsic genomic factors of the plant that hinder bud development.
• Endo-dormancy: It depends on the accumulated chilling hours (CHH). It can be deep dormancy or facultative dormancy, which corresponds to a state in which the plant can break dormancy under appropriate conditions.
• Eco-dormancy: Dependent on heat accumulation (RC) in phenological phases close to flowering.

During ecodormancy, trees require the accumulation of heat units to initiate the growing season. Once both requirements (RF and CR) are met, the plant can show signs of growth (budding and/or flowering) in late winter and early spring.

After studies of the dormancy phases, correlated assets are quantified in these phases, contrasting that the concentration of carbohydrates concludes in high levels of starch associated with the deep dormancy state, while high levels of hexoses (glucose plus fructose) are related to the exit from dormancy, this being ratified by results analysis in a probabilistic model.

Thus, dormancy in deciduous trees is seen as a complex process regulated by a large number of factors, including gene expression, protein synthesis, and structural changes in the cell and other units.

In conclusion, we will state that deciduous fruit trees need an accumulation of cold to emerge from the state of rest of Endo-dormarcia (greater relevance), and this strategy of accumulating cold hours is actually a defense mechanism to avoid sprouting when environmental conditions are unfavorable during the winter period, which would leave the young shoots defenseless against subsequent frosts of the season.

To understand phenological self-regulation, we must first understand its definition and the negative effects of its absence in deciduous crops.

Well, when we talk about “chill hours” (CH), we are referring to the amount of time (hours) that the plant has been below a temperature of 7 ° CChilling hours or units (HU) represent one hour of exposure to temperatures suitable for the plant to emerge from dormancy. The amount of chilling required varies by species and variety.

The lack of accumulation of cold hours generates multiple and varied imbalances in the physiological self-regulation and phenological calendar of sprouting, flowering and fruiting of the plant, such as:

• Delay in production.
• Increased vegetative growth and excessive use of reserves.
• Less “darts or matches” in stone fruit trees.
• Poor leaf development.
• Uneven and delayed sprouting.
• Dormant vegetative buds.
• Weakness in outbreaks.
• Vertical development due to lack of open lateral buds.
• Flowers Delayed and uneven flowering.
• Less fruit set due to mismatch in flowering times.
• Weak flower drop. Pollen viability decreases.
• Bud drop in susceptible trees.
• Fruits Irregular ripening.
• Lower productions.
• Lower fruit quality: size, color and firmness.

In light of this, we must understand and take into account possible palliatives as precedents.

If we take as a precedent that, although dormancy depends, as we have said, mainly on the climate of the campaign, it is also strongly influenced by endogenous factors of phytoregulation, which implies an unbalanced concentration between development promoters (auxins, gibberellins and cytokinins) against inhibitory active ingredients (abscisic acid), it involves breaking or interrupting the dormancy and sprouting of the bud.

The objective, therefore, is to try to biostimulate, through sprouting promoters or cold compensators, the metabolic pathways involved in enzymatic synthesis that participate in the hormonal promotion of bud activation, since these will be naturally inactive due to the absence of cold hours, this being an increasingly common case in all areas belonging to the subtropics.

Under this Biostimulation, several different objectives will therefore be sought:

• Precocity, through early flowering.
• Achieving greater overall uniformity in flowering and leaf formation in a balanced manner, since, as is known, each bud usually has its own dormant conditions depending on whether it is lateral or terminal or its vegetative or floral phenology.

 

In this regard, at Cultifort we can influence the emergence of dormancy through promoters and nutritional supports based on nitrogenous, potassium, calcium active ingredients or, with greater relevance to the aforementioned, with high levels of precursorcytokinin, which can promote processes involved in the variables mentioned, such as:

• They stimulate mitosis.
• Produces an increase in the synthesis of polynucleotides
• It promotes the elongation of fruits and seeds.
• Breaking of lethargy.
• Induction of shoot formation.
• Improved flowering.
• Alteration in fruit growth.
• Rupture of apical dominance.
• Promote lateral branching.
• Homogenization of size and shape, improving harvest uniformity.
• Induce parthenocarpy in some fruits.
• They replace the need for red light.
• Break dormancy.
• They decrease alkaloid content.
• They promote the formation of shoots in in vitro culture.
• Stimulate the precocity and advancement of generative and vegetative cycles.
• They act in the translation of RNA.
• They increase the speed of protein synthesis and enzymes.
• Increase and induce cell division and organ formation.
• Induce the development of lateral buds.
• Stimulate flowering of short-day plants.
• Red light replacement in photoblastic seed germination.

Cultifort suggests a strategy to support dormancy breaking and mitigate the negative effects of a lack of cold hours, based on the combination of two synergistic formulations for such objectives.

BVC EVOLUTION (Formerly BVC 2021)

The combined action of amino acids, nitrogen, and reducing sugars promotes protein and carbohydrate synthesis, prompting the onset of plant physiological activity, stimulating the formation of leaves and flowers, improving fruit quality, and accelerating ripening and production. The seaweed included in BVC 2021 contains mineral salts, vitamins, essential oils, proteins, and cytokinin precursors; essential for cell division and the formation of new tissues.

FASKOLOR

Liquid formulation of potassium, organic acids and selected peptide complexes, whose special balance provides a notable increase in the precocity of generative processes.

In addition to the role of osmotic regulation, sugar increase and potassium color, a selection of peptide complexes accelerate specific physiological cycles to enter generative phenologies.

Furthermore, the organic acids contained in FASKOLOR promote rapid assimilation and translocation in the plant, increasing the effectiveness of applications and improving the response, both of its composition and the synergy in this case of the BVC 2021 active ingredients.