Phosphorus (P) deficiency is one of the main reasons limiting plant production of Brassica napus L. Exploring the dynamics of leaf intracellular substances and the correlations with photosynthesis and growth helps to understand the response mechanisms of B. napus L. to P deficiency. This study conducted experiments on B. napus L. plants by measuring the leaf electrophysiological parameters, leaf structure, elastic modulus (E_m), photosynthesis, and growth indices under different P treatment conditions. The dynamics of leaf intracellular water and nutrients of B. napus L. were calculated and analyzed by using the electrophysiological parameters, and the plant tolerance threshold to low-P stress was discovered. The results indicated that the status of the leaf intracellular water and nutrients remained stable when the P concentration was not lower than 0.250 mmol·L⁻¹, but maximized the photosynthesis and growth at a P level of 0.250 mmol·L⁻¹. The 0.125 mmol·L⁻¹ P concentration significantly decreased the mesophyll cell volume, and the palisade–sponge ratio and tightness degree of leaf tissue structure were remarkably increased. This led to an increase in cell elastic modulus, and significantly improved the water retention capacity of leaf cells. At the same time, the intracellular water use efficiency and total nutrient transport capacity of leaves remained stable. As a result, the photosynthesis and growth of plants were maintained at the same level as that of the control group. However, photosynthesis and growth were clearly inhibited with a further decrease in P concentration. Therefore, 0.125 mmol·L⁻¹ was the tolerance threshold of B. napus L. to low P. With the help of electrophysiological information, the effects of the dynamics of intracellular substances on photosynthesis and growth of B. napus L. under low-P stress can be investigated, and the plant’s adaptive response can be revealed. However, the findings of the current hydroponic study are not directly applicable to field conditions with naturally P-deficient soils.

Mangroves are landscape plants in coastal parks and are also typical salt-tolerant plants. Water–salt transport plays a key role in their adaptations to salinity. This research aims to study the synchronous dynamics of intracellular water–salt and plant adaptation mechanisms. Therefore, no salt and three salinity gradients, including 0.1, 0.2, and 0.4 mol/L NaCl, were applied to three mangrove plants. An electrophysiological sensor was used to non-invasively detect plant electrical signals. The results showed that mangroves’ water and salt dynamic characteristics differed under salt treatment. Rhizophora stylosa reduced the cytoplasmic salt by increasing water absorption, enhancing salt exclusion, and decreasing salt inflow. Kandelia candel managed salt by transferring it into a vacuole, diluting the intracellular salt concentrations through increased cell fluid while maintaining the salt exclusion capacity as salinity increased. Aegiceras corniculatum decreased the cellular salt influx and adapted to 0.4 mol/L NaCl by activating salt secretion. In addition, water-use, salt transport, cellular endogenous convertible energy, and photosynthetic gas exchange parameters could be used as representative factors for salt adaptation of these mangrove species. The results deepen our understanding of plant salt tolerance mechanisms and provide a new approach for timely determining plant adaptability.

The integration of physical and chemical processes underpins life. Plant cells function as bioelectrical units, storing and converting energy through capacitive, inductive, and resistive properties. This study elucidates the electrophysiological and molecular mechanisms governing salt transport and energy allocation in Aegiceras corniculatum leaves under combined salinity-waterlogging stress (T1: 0.1 M NaCl + 2 h; T2: 0.2 M NaCl + 4 h; T3: 0.4 M NaCl + 6 h). Results demonstrate that leaf intracellular water-salt transport dynamics, coupled with salt-transport gene expression, coordinately regulate active/passive transport, vacuolar compartmentalization, cytoplasmic Na+ levels, and excretion. High salinity reduced salt excretion rate/capacity (LISTR/LISTC) and downregulated SOS1, while impairing water-holding capacity (LIWHC) and transport activities. Concurrent VHAc1 upregulation elevated vacuolar H+, inhibiting the Na+/H+ antiporter and compromising vacuolar salt sequestration. With increasing stress intensity, energy allocation shifted toward stress responses. Both electrical (internal) energy and ATP-derived chemical energy---originating from photosynthesis---jointly sustain plant vitality and adaptability; growth is primarily supported by internal energy, and adaptive differences dictate photosynthetic performance. This integrated analysis reveals how water-salt dynamics and molecular regulation confer salt tolerance in mangroves, offering insights crucial for coastal ecosystem resilience.