Cytokinin‐promoted secondary growth and nutrient storage in the perennial stem zone of Arabis alpina

Abstract

Perennial plants maintain their lifespan through several growth seasons. Arabis alpina serves as a model Brassicaceae species to study perennial traits. Lateral stems of A. alpina have a proximal vegetative zone with a dormant bud zone and a distal senescing seed-producing inflorescence zone. We addressed how this zonation is distinguished at the anatomical level, whether it is related to nutrient storage and which signals affect the zonation. We found that the vegetative zone exhibits secondary growth, which we termed the perennial growth zone (PZ). High-molecular-weight carbon compounds accumulate there in cambium and cambium derivatives. Neither vernalization nor flowering were requirements for secondary growth and the sequestration of storage compounds. The inflorescence zone with only primary growth, termed the annual growth zone (AZ), or roots exhibited different storage characteristics. Following cytokinin application cambium activity was enhanced and secondary phloem parenchyma was formed in the PZ and also in the AZ. In transcriptome analysis, cytokinin-related genes represented enriched gene ontology terms and were expressed at a higher level in the PZ than in the AZ. Thus, A. alpina primarily uses the vegetative PZ for nutrient storage, coupled to cytokinin-promoted secondary growth. This finding lays a foundation for future studies addressing signals for perennial growth.

Arabis alpina: A perennial model plant for ecological genomics and life‐history evolution

“…Arabis alpina has also been used to study further developmental traits (exemplified in Figure 2 ), which include leaf trichome formation (Chopra et al, 2014 , 2019 ), leaf senescence (Wingler et al, 2012 , 2015 ), secondary growth (Sergeeva, Liu, et al, 2021 ; Sergeeva, Mettler‐Altmann, et al, 2021 ) and adventitious rooting (Mishra et al, 2020 ). For the last of these, natural variation has been detected under controlled environmental conditions (Mishra et al, 2020 ).…”

“…While for some ecologically relevant and naturally variable traits, such as the timing of flowering, the molecular genetic basis is already well understood, other traits still await detailed molecular characterization, for example those regulating frost tolerance through the accumulation of metabolites in leaves (Kolaksazov et al, 2017 ). Storage compounds are deposited exclusively in the perennating parts of the plant that also exhibit secondary growth (Sergeeva, Liu, et al, 2021 ; Sergeeva, Mettler‐Altmann, et al, 2021 ). Some storage compounds, such as sucrose, confer higher tolerance to cold stress in plants from high elevations, while leading to accelerated leaf senescence in plants from low elevation (Wingler et al, 2012 , 2015 ).…”

Coordinated Patterns in the Allocation, Composition, and Variability of Multiple Elements Among Organs of Two Desert Shrubs Under Nitrogen Addition and Drought

“…This may be due to increased water availability stimulating root growth to improve multiple nutrients' uptake (Zhang et al 2020). Conversely, drought stress enhanced the distribution of elements to above-ground parts, especially stems, suggesting a greater investment there to cope with harsh conditions and increase resource acquisition, for which stems may function as nutrient pools (Sergeeva et al 2021). Under drought stress, compared to stems and roots, the lower distribution of elements to short-lived leaves may indicate that A. sparsifolia seedlings employ an adaptive strategy to prolong multi-elements' residence time for future usage.…”

Species identity and resource availability explain variation among above and below-ground functional traits in Himalayan temperate forests

“…Increased coordination among organs in coniferous species showed increased plasticity with topographical heterogeneity (Huo et al, 2021). For broad-leaved species, a strong correlation with soil water availability (MC) suggested increased nutrient allocation in belowground parts, especially fine roots as a mechanism to fight against drought and resource scarcity (Körner, 2021;Sergeeva et al, 2021). Though this allocation might come at the cost of reduced biomass allotment to reproductive parts and photosynthetic organs (Ma et al, 2017).…”