Non‐structural carbohydrate dynamics associated with antecedent stem water potential and air temperature in a dominant desert shrub

Abstract

Non-structural carbohydrates (NSCs) are necessary for plant growth and affected by plant water status, but the temporal dynamics of water stress impacts on NSC are not well understood. We evaluated how seasonal NSC concentrations varied with plant water status (predawn xylem water potential, Ψ) and air temperature (T) in the evergreen desert shrub Larrea tridentata. Aboveground sugar and starch concentrations were measured weekly or monthly for~1.5 years on 6-12 shrubs simultaneously instrumented with automated stem psychrometers; leaf photosynthesis (A net ) was measured monthly for 1 year. Leaf sugar increased during the dry, premonsoon period, associated with lower Ψ (greater water stress) and high T. Leaf sugar accumulation coincided with declines in leaf starch and stem sugar, suggesting the prioritization of leaf sugar during low photosynthetic uptake. Leaf starch was strongly correlated with A net and peaked during the spring and monsoon seasons, while stem starch remained relatively constant except for depletion during the monsoon. Recent photosynthate appeared sufficient to support spring growth, while monsoon growth required the remobilization of stem starch reserves. The coordinated responses of different NSC fractions to water status, photosynthesis, and growth demands suggest that NSCs serve multiple functions under extreme environmental conditions, including severe drought. K E Y W O R D S antecedent conditions, carbon-water relations, creosote bush, plant water potential, starch, sugar

Growth and Nutritional Quality of Lemnaceae Viewed Comparatively in an Ecological and Evolutionary Context

“…Yet, other terrestrial plants, such as palm trees or mesquite, have deep roots that access the ground-water table [50][51][52][53][54], which supports steady growth despite low rainfall or moisture level in the air. Pronounced osmotic adjustment [55] and expansion of root volume [56] is also employed by terrestrial plants that grow very slowly in areas with extremely low water availability (Table 1).…”

Amplifying effects of recurrent drought on the dynamics of tree growth and water use in a subalpine forest

“…As a result, the significant reduction in starch concentration in shoots during the third drought treatment (Figure 6, Supporting Information: Figure ), which was similarly also reported for P. abies at a low elevation site exposed to a severe natural drought event (Arend et al, 2021), does not provide an indication of reduced phloem transport to sink organs. Because the concentrations of soluble sugars and total NSC were increased in needles and branches of drought‐exposed P. abies (Figure 6), the reduction in starch content more likely reflected an active conversion to osmotically active sugars, and therefore a prioritisation of osmotic regulation of water potential over C storage (Guo et al, 2020). The accumulation of osmotically active sugars has been observed repeatedly as a drought response in leaves, involving the conversion of starch as well as a preferential allocation of recently assimilated C to sugars (Chaves et al, 2003; Hartmann, Ziegler, Trumbore et al, 2013; Hasibeder et al, 2015; Nio et al, 2011).…”

Variation of non‐structural carbohydrates across the fast–slow continuum in Amazon Forest canopy trees

“…Non‐structural carbohydrates are the major form of energy storage in many plant species and have been shown to play a critical role in maintaining hydraulic function and enhancing survival during drought (Guo et al., 2020; Liu et al., 2018; O'Brien et al., 2014; Tomasella et al., 2017). Starch and soluble sugars comprise the most significant portions of NSC reserves in most tree genera (Martínez‐Vilalta et al., 2016), but other compounds such as lipids also play an important role as storage (Herrera‐Ramírez et al., 2021; Hoch et al., 2003).…”