2026 TT MBiol2
Dr Tin Hang (Henry) Hung [email protected]
Prof John MacKay [email protected]
Dr Erola Fenollosa [email protected]
Pedunculate oak (Quercus robur)
Hazel (Corylus avellana)
Excess forest mortality is consistently linked to drought worldwide. Adaptation to drought has a complex underlying mechanism and has trade-offs with other life history traits. In particular, water regulation is closely related to photosynthetic activity and has significant effects on growth.
Today we will be studying two native broadleaf species widely bred and grown in the UK: pedunculate oak and hazel. We will characterise and compare their drought responses.
<aside> ⁉️ Question 1
There are three hypothesised mechanisms underlying tree mortality, based on the relationship between the temporal length of drought (duration) and the relative decreased in water availability (intensity) in the hydraulic framework.
Carbon starvation can occur when drought duration is long enough to curtail photosynthesis longer than the equivalent storage of carbon reserves for maintenance of metabolism.
Hydraulic failure is when drought intensity pushes a plant past its threshold for irreversible desiccation before carbon starvation occurs.
Biotic agents (herbivory and diseases) can amplify or be amplified by both carbon starvation and hydraulic failure.
The cohesion-tension theory explains how water moves up across the xylem. Water on the surface of mesophyll cells saturates the cellulose microfibrils of the primary cell wall. The water vapor on the surface of cell walls evaporates into the internal air spaces. This negative pressure by tension pulls on the water in the xylem vessels.
<aside> ⁉️ Question 2
