Effects of pH on ammonium uptake byTypha latifoliaL.

Abstract

The effects of solution pH on NH4+ uptake kinetics and net H+ extrusion by Typha latifolia L. were studied during short‐term (days) and long‐term (weeks) exposure to pH in the range of pH 3.5–8.0. The NH4+ uptake kinetics were estimated from depletion curves using a modified Michaelis‐Menten model. T. latifolia was able to grow in solution culture with NH4+ as the sole N source and to withstand a low medium pH for short periods (days). With prolonged exposure (weeks) to pH 3.5, however, the plants showed severe symptoms of stress and stopped growing. The solution pH affected NH4+ uptake kinetics. The affinity for NH4+, as quantified by the half saturation constant (K1/2) and Cmin (the NH4+ concentration at which uptake ceases), decreased with pH. K1/2 was increased from 7.1 to 19.2 mmol m−3 and Cmin from 2.0 to 5.7 mmol m−3 by lowering the pH in steps from 8.0 to 3.5. Vmax was, however, largely unaffected by pH (∼22 μmol h−1 g−1 root dry weight). Under prolonged exposure to constant pH, growth rates were highest at PH 5.0 and 6.5. At pH 8.0 growth was slightly depressed and at pH 3.5 growth completely stopped. NH4+ uptake kinetics were similar at pH 5.0, 6.5 and 8.0 whereas at pH 3.5 NH4+ uptake almost completely stopped. The ratio between net H+ extrusion and NH4+ uptake decreased significantly at low pH. The adverse effects of low pH on NH4+ uptake kinetics are probably a consequence of a reduced H+‐ATPase activity and/or an increased re‐entry of H+ at low pH, and the associated decrease in the electrochemical gradient across the plasma membranes of the root cells.

Acclimation of photosynthesis to supersaturated CO2 in aquatic plant bicarbonate users

“…A low pH in the water and sediment can reduce the nitrogen uptake capacity of reed plants (Dyhr‐Jensen & Brix, ), and this effect cannot be ruled out in our study. However, the ammonia uptake of Typha latifolia was constant across the pH range of 5–8 (Dyhr‐Jensen & Brix, ), which is wider than the pH range from 6.7 to 8.2 in the waters of our study. Aquatic plants can influence sediment pH (Blossfeld & Gansert, ) and thus limit the pH effects on nutrient uptake.…”

“…Under field conditions, high nutrient availabilities often result in more luxuriant plant growth and stronger CO 2 depletion, which activates the CCM mechanisms and, thus, increases nitrogen demands. A low pH in the water and sediment can reduce the nitrogen uptake capacity of reed plants (Dyhr‐Jensen & Brix, ), and this effect cannot be ruled out in our study. However, the ammonia uptake of Typha latifolia was constant across the pH range of 5–8 (Dyhr‐Jensen & Brix, ), which is wider than the pH range from 6.7 to 8.2 in the waters of our study.…”

A New Approach for Tracking Vegetation Change after Restoration: A Case Study with Peatlands

“…However, Sphagnum has the capacity to acidify its environment (Clymo 1964); therefore, the pH should decrease toward values more typical of bog waters over time (below 4.2; Vitt & Chee 1990). Typha latifolia has already started to decrease in both restored ditches and peat fields (Appendix S2), possibly in more acidic areas as it loses its capacity to uptake nitrates at pH 3.5 (Dyhr‐Jensen & Brix 1996). The Facultative wetland species Calamagrostis canadensis also differentiated the restored sites from the references ecosystem where it was not frequently found.…”

Regulation of gene expression in roots of the pH-sensitive Vaccinium corymbosum and the pH-tolerant Vaccinium arboreum in response to near neutral pH stress using RNA-Seq

“…In response, the expression of genes whose products are involved in cell wall reinforcement, such as pectin esterases and arabinogalactan proteins is upregulated [ 15 ]. Exposure to low pH also leads to plasma membrane depolarization [ 16 ], reduction of proton extrusion by plasma membrane H + -ATPases [ 17 ], and enhancement of the relocation of excess H + from the cytosol to the vacuole through vacuolar V-H + -ATPase and V-H + -pyrophosphatase pumps [ 18 ]. Other means of cytosolic pH homeostasis, such as glutamate decarboxylation [ 19 ], might also be involved.…”