Abstract
Allocation of biomass to different organs is a fundamental aspect of plant responses and adaptations to changing environmental conditions, but how it responds to nitrogen (N) and phosphorus (P) availability remains poorly addressed. Here we conducted greenhouse fertilization experiments using Arabidopsis thaliana, with five levels of N and P additions and eight repeat experiments, to ascertain the effects of N and P availability on biomass allocation patterns. N addition increased leaf and stem allocation, but decreased root and fruit allocation. P addition increased stem and fruit allocation, but decreased root and leaf allocation. Pooled data of the five levels of N addition relative to P addition resulted in lower scaling exponents of stem mass against leaf mass (0.983 vs. 1.226; p = 0.000), fruit mass against vegetative mass (0.875 vs. 1.028; p = 0.000), and shoot mass against root mass (1.069 vs. 1.324; p = 0.001). This suggested that N addition relative to P addition induced slower increase in stem mass with increasing leaf mass, slower increase in reproductive mass with increasing vegetative mass, and slower increase in shoot mass with increasing root mass. Further, the levels of N or P addition did not significantly affect the allometric relationships of stem mass vs. leaf mass, and fruit mass vs. vegetative mass. In contrast, increasing levels of N addition increased the scaling exponent of shoot to root mass, whereas increasing levels of P addition exerted the opposite influence on the scaling exponent. This result suggests that increasing levels of N addition promote allocation to shoot mass, whereas the increasing levels of P addition promote allocation to root mass. Our findings highlight that biomass allocation of A. thaliana exhibits a contrasting response to N and P availability, which has profound implications for forecasting the biomass allocation strategies in plants to human-induced nutrient enrichment.
Highlights
Allocation of biomass to different organs is a core component of plant life history and plays a pivotal role in the trade-off between resource acquisition and utilization (Bazzaz and Grace, 1997; Weiner, 2004; Eziz et al, 2017)
We examined the effects of N and P availability on the biomass allocation of Arabidopsis thaliana, which is a model annual plant for molecular biological studies (Meinke et al, 1998)
This study aimed to address the following questions: (i) how do N and P availability affect the biomass allocation fractions? and (ii) how do N and P availability regulate the allometric relationships of biomass among different organs? Considering the differential roles of N and P in physiological functions and metabolic processes in plants, we hypothesize that (i) N addition increase leaf and stem allocation but decrease root and fruit allocation, whereas P addition increase stem and fruit allocation but decrease root and leaf allocation; (ii) N addition relative to P addition results in lower scaling exponents of stem mass against leaf mass, fruit mass against vegetative mass, and shoot mass against root mass
Summary
Allocation of biomass to different organs is a core component of plant life history and plays a pivotal role in the trade-off between resource acquisition and utilization (Bazzaz and Grace, 1997; Weiner, 2004; Eziz et al, 2017). Previous studies have reported the effects of nutrient or N availability on biomass allocation (e.g., Bazzaz and Grace, 1997; Müller et al, 2000; Shipley and Meziane, 2002; Poorter et al, 2012; Fujita et al, 2014), with little knowledge about the responses of biomass allocation to varying P availability (but see Luo et al, 2016). Considering the tightly coupled relationship between N and P and the imbalance of N vs P inputs induced by human activities, it is imperative to disentangle the effects of N and P availability on biomass allocation concurrently
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