How different pruning severities alter shoot structure: a modelling approach in young 'Nonpareil' almond trees

Area of Science:

• Plant science
• Arboriculture
• Developmental biology

Background:

• Shoot structure, defined by axillary meristem fate, is generally consistent within tree genotypes.
• Limited understanding exists regarding shoot structural plasticity after horticultural interventions like pruning.

Purpose of the Study:

• To investigate the impact of pruning severity on almond (Prunus dulcis) shoot structure.
• To analyze the structure of regrowth shoots and pruned shoots.
• To determine if regrowth shoots replicate the structure of original shoots before pruning.

Main Methods:

• Applied three levels of pruning severity to almond shoots.
• Assessed shoot structures using hidden semi-Markov models of axillary meristem fates.
• Analyzed both 1-year-old regrowth shoots and the 2-year-old pruned shoot portions.

Main Results:

• Pruning severity significantly influenced the structure of both regrowth and pruned shoots.
• Regrowth shoots exhibited more complex structures under severe pruning but were simpler than original shoots, indicating age-related simplification.
• Pruned shoot structure was affected by pruning intensity, prior shoot structure, and bud competition.

Conclusions:

• Pruning significantly alters almond shoot structure in a predictable manner.
• Shoot structure demonstrates plasticity in response to pruning severity.
• Tree age may contribute to a progressive simplification of shoot structure.