Prolonged exposure to centrifugal acceleration increases biomass and alters biomass allocation in Arabidopsis thaliana (L.) Heynh. with no apparent impact on elemental concentration in the shoot system

Abstract

Previous studies have shown that plants can complete their life cycle under microgravity. However, the effects of long-term exposure to altered gravity conditions, including microgravity, on most of the biological processes of a plant's life cycle remain largely unexplored. Given the limited opportunities for space experiments, ground-based experiments using altered gravity conditions have been conducted. To investigate the longer-term effects of centrifugal acceleration, we have developed and utilized a custom-built centrifugal cultivation system using a centrifuge equipped with lighting, enabling the continuous growth of seed plants under centrifugal acceleration. In this study, we examined the effects of 10 g centrifugal acceleration on the biomass of the shoot system (stems and rosette leaves) and the root system of Arabidopsis thaliana for the first time, covering the entire cultivation period from germination to 40 days. Our results showed that the dry mass of the stem per unit length was significantly larger under 10 g compared to the 1 g control, indicating a typical gravity resistance response of the stem. Moreover, the total dry mass of the stems, rosette leaves, and roots was larger under 10 g centrifugal acceleration compared to the 1 g control, suggesting an increase in biomass at the individual plant level. We also observed that the leaf mass per area of the rosette leaf was larger under centrifugal acceleration compared to the 1 g control, indicating enhanced photosynthesis rates in Arabidopsis and resulting in increased biomass of individual plants. In terms of biomass allocation, both root-shoot ratio and root mass fraction were significantly higher under centrifugal acceleration compared to the 1 g control. Furthermore, we measured the concentration of mineral elements in the main stem and rosette leaves using inductively coupled plasma optical emission spectrometry. Despite the increase in dry mass of the root system, we found no significant differences in the concentration of any of the ions between 10 g and 1 g conditions, indicating that mineral nutrient uptake homeostasis is maintained even under centrifugal acceleration.