Abstract Detail

Ecophysiology

Shao, Jianfei [1], Maherali, Hafiz [2].

Root trait plasticity in response to contrasting phosphorus environments and its consequences for plant performance.

There is no consensus on the mechanisms driving the diversification of plant root functional traits such as root diameter, root branching, specific root length (SRL) and root tissue density (RTD), which are known to vary significantly across plant populations, species, families, and growth forms in nature. One hypothesis is that adaptations like increased root biomass allocation, root depth and development of finer root systems with high absorptive capacity are associated with soil that are low in essential nutrients like phosphorus (P). However, few studies have examined root trait plasticity in response to P and its consequences for plant performance in natural populations. If P limitation triggers the development of roots with higher absorptive capacity, low P conditions should lead to the expression of higher SRL, higher root branching, higher RTD and lower root diameter compared to plants under high P. In addition, plants with lower SRL, thicker root diameter, lower branching and lower RTD should be favoured in high P condition, and these traits should be selected for based on plant performance; for plants under low P condition, the opposite applies. To test these hypotheses, we grew 34 natural genetically distinct inbreeding Medicago truncatula (annual Mediterranean legume) populations under controlled conditions. We exposed plants to high and low P fertilization treatments and harvested them after 8 weeks. All plants increased biomass under high P conditions; plants grown under low P generally had higher root: shoot ratio. While all root functional traits varied significantly among populations under both resource conditions; differing P availability did not affect the expression of root diameter and RTD. However, under low P, plants expressed higher SRL, and lower branching compared to those under high P. We found performance based selection for lower SRL under high P, which is consistent with the direction of plasticity in this trait. These results suggest that P availability is a potential cause of diversification in root traits. Future studies will explore how root allocation and morphology evolve in response to interactions with arbuscular mycorrhizal fungi, which engage in a nutritional mutualism with plants and may therefore also alter selection on root traits.

1 - 75 Southcreek Trail, Guelph, ON, N1G5A7, Canada
2 - University Of Guelph, Department Of Integrative Biology, 50 Stone Road East, Guelph, ON, N1G 2W1, Canada

Keywords:
Trait evolution
Functional trait
Root morphology
Plant root
Physiology
arbuscular mycorrhizal fungi
symbiosis
Plant Nutrient
plant evolution
Plant ecology.

Presentation Type: Oral Paper
Session: ECOPH2, Ecophysiology II
Location: /
Date: Tuesday, July 20th, 2021
Time: 11:30 AM(EDT)
Number: ECOPH2007
Abstract ID:441
Candidate for Awards:Physiological Section Physiological Section Li-COR Prize,Physiological Section Best Paper Presentation