Interspecific morphological variation in Juglandoideae resting bud organization: a winter's tale?

Area of Science:

• Plant Biology
• Botany
• Ecology

Background:

• Dormant resting buds are typically viewed as static structures with protective outer cataphylls and inner embryonic leaves.
• The influence of cataphylls on the cyclical, seasonal leaf form development from resting buds has been understudied.
• Investigating the link between dormant bud structure and growing season development is crucial for understanding plant life cycles.

Purpose of the Study:

• To compare the seasonal heteroblastic leaf form sequences in six temperate Juglandaceae species.
• To examine how distinct vegetative resting bud structures (with, without, or caducous cataphylls) affect leaf development.
• To understand the relationship between dormant bud morphology and summer shoot ontogeny and functional strategies.

Main Methods:

• Tracking 2249 vegetative metamers over a 7-month growing season in a common garden setting.
• Utilizing micro-CT scanning to investigate the timing of metamer initiation within terminal buds.
• Estimating character state transitions of resting bud types using a phylogenetic tree of Juglandaceae.

Main Results:

• Buds with cataphylls exhibit a determinate growth pattern with synchronous flushing and abscission of a single foliage leaf cohort.
• Buds lacking cataphylls display a staggered pattern of shorter-lived foliage leaf appearance and abscission.
• All studied heteroblastic sequences produce small, caducous leaf forms preceding terminal bud set, regardless of cataphyll presence.

Conclusions:

• The presence or absence of cataphylls in resting buds signifies distinct shoot ontogenetic patterns and summer functional strategies.
• Caducous leaf forms in Juglandoideae suggest the importance of shoot tip protection extending beyond the dormant season.
• Resting bud structure is a key indicator of developmental pathways and ecological adaptations in Juglandaceae.