Root respiratory costs of ion uptake, root growth, and root maintenance in wetland plants: efficiency and strategy of O2 use for adaptation to hypoxia

Abstract

Oxygen use in roots is an important aspect of wetland plant ecophysiology, and it depends on the respiratory costs of three major processes: ion uptake, root growth, and root maintenance. However, O2 allocation in wetland plants has received little attention. This study aimed to determine the O2 allocation and specific respiratory cost of each process under hypoxic conditions, to better understand the strategy and efficiency of O2 use in wetland plants. The root respiration rate, nitrogen uptake, and root growth in three Carex species with different growth rates were examined under hypoxic conditions using different N sources, and the respiratory costs of ion uptake, root growth, and root maintenance were statistically estimated. All species exhibited low specific costs and low ratios of O2 allocation for root growth (2.0 ± 0.4 mmol O2 g(-1) and 15.2 ± 2.7 %, respectively). The specific cost of ion uptake was 20-30 % lower in fast-growing species than in slow-growing species. As plant growth rate increased, the O2 allocation ratio for ion uptake increased, and that for root maintenance decreased. The cost was higher when NO3 (-) was fed, than when NH4 (+) was fed, although the pattern of O2 allocation ratios for three processes was similar for NO3 (-) and NH4 (+). Our results indicate that wetland plants primarily employ an O2 use strategy of minimising the respiratory costs of root growth, and fast-growing plants specifically use O2 to maximise ion uptake. These findings provide new insights into ecophysiological behaviours of roots in adaptation to hypoxia.

Tolerant mechanisms to O2 deficiency under submergence conditions in plants

“…occultans, and C. middendorffii) are grown in the sole NH 4 + treatment under low O 2 condition, they exhibit a smaller root to shoot weight ratio (i.e., high S/R ratio) and increased net N uptake rate per unit root weight (NNUR) compared to the sole NO 3 − treatment. This high S/R ratio can lead to the decrease in the whole-root O 2 consumption in the sole NH 4 + treatment (Nakamura and Nakamura 2016;Nakamura et al 2010Nakamura et al , 2013 (Fig. 5).…”

“…This saving of energy consumption by the aerenchyma formation may increase the allocation of the respiratory energy to other processes such as root growth and nutrient uptake. Some wetland plants with developed aerenchyma allocate their root respiratory ATP to maximize the N uptake instead of root maintenance and growth (Nakamura and Nakamura 2016). Such root responses in wetland plants could be their strategy for efficient O 2 consumption and high N acquisition for adapting to O 2 deficiency.…”

“…Moreover, it was recently reported that the root O 2 consumption strategies related to nitrogen (N) acquisition differ among species with differences in their ability to O 2 supply to the roots. The differences in strategies are associated with the differences in the O 2 demand by the aerobic respiration for root growth and N acquisition (Nakamura and Nakamura 2016;Nakamura et al 2013). The N acquisition traits linked to the O 2 supply ability could relate to the hypoxia and anoxia tolerance in wild wetland species.…”

Literatuuronderzoek chrysantenteelt zonder stomen : Kan een monocultuur in een stabiel microbieel evenwicht blijven?

“…al., 2005). De hogere gevoeligheid voor Pythium en ook Phytophtora is een gevolg zijn van de betere bereikbaarheid van de wortels voor de zwemsporen die een kenmerk zijn van juist deze beide schimmels (van der Gaag, 2005), gecombineerd met een grotere gevoeligheid van cellen die door zuurstofgebrek niet genoeg elementen kunnen opnemen voor de opbouw van celwanden (Nakamura et. al., 2016; Bar-Yosef en Lieth, 2013).…”

Keep Calm and Survive: Adaptation Strategies to Energy Crisis in Fruit Trees under Root Hypoxia

“…The growth and maintenance of tissues are two processes that require energy from root respiration, and must coexist coordinately for the correct development of plants. However, energy crisis caused by hypoxia/anoxia stress (O 2 deficiency) induces an energy redistribution either to the maintenance or the growth of new tissue [ 74 , 137 ]. Membrane stability, active ion transport and de novo synthesis of proteins are the most expensive processes whereby the cell metabolism must adjust its energy budget [ 138 ].…”