Metabolic indices related to leaf marginal necrosis associated with potassium deficiency in tomato using GC/MS metabolite profiling

Preliminary study on the diagnosis of NK stress based on the puncture mechanical characteristics of cucumber stem

To investigate the relationship between stem puncture mechanical characteristics and NK stress diagnosis, the microstructure, surface morphology, cellulose and lignin content, puncture mechanical characteristics, and epidermal cell morphology of cucumber stems were measured herein. The results indicated that the middle stem, which had a diameter of approximately 7000 μm, was more suitable for puncturing due to its lower amount of epidermal hair, and its gradual regularity in shape. Further, the cucumber stems were protected from puncture damage due to their ability to rapidly heal within 25 h.. The epidermal penetration of the cucumber stems increased with the increase in cellulose and lignin, though cellulose played a more decisive role. The epidermal break distance increased with an increase in N application and decreased with an increase in K+ application, but the change in intercellular space caused by K+ supply was the most critical factor affecting the epidermal break distance. In addition, a decrease in K+ concentration led to a decrease in epidermal brittleness, whereas the factors affecting epidermal toughness were more complex. Finally, we found that although the detection of epidermal brittleness and toughness on nutrient stress was poor under certain treatment, the puncture mechanical characteristics of the stem still had a significant indicative effect on N application rate. Therefore, elucidating of the relationship between the puncture mechanical characteristics of the stems and crop nutritional stress is not only beneficial for promoting stem stress physiology research but also for designing on-site nutritional testing equipment in the future.

DMPP and Polymer-Coated Urea Promoted Growth and Increased Yield of Greenhouse Tomatoes

Improvements in nitrogen (N) use efficiency reduce stress on the environment and improve tomato production. A two-year trial was conducted in greenhouse tomatoes with a split-plot design, in which one factor was the N application rate (150 kg·ha−1, N1; 200 kg·ha−1, N2; and 250 kg·ha−1, N3) and two other factors were the type of urea applied (urea, T1; slow-release (polymer-coated) urea, T2, and nitrification inhibitors (3,4-dimethylpyrazole phosphate, DMPP) + urea, T3); no N fertilizer was applied in the control. The effects of the nitrogen (N) application rate and type of urea applied on the root morphology indexes, growth indexes, photosynthetic parameters, yield (Y), water use efficiency (WUE), and nitrogen agronomic efficiency (NAE) of greenhouse tomatoes were investigated. The results show that an appropriate N application rate (200 kg·ha−1) can improve tomato growth and net photosynthetic rate (Pn). With T3, the Y and WUE of greenhouse tomatoes first increased and then decreased as the N application rate increased, but with T1 and T2, the Y and WUE increased as the N application rate increased. The NAE of greenhouse tomatoes was significantly lower with N3 than with N2. The root growth, plant growth, Pn, Y, WUE, and NAE of the tomatoes were improved with T2 and T3 compared to T1. These findings can be used to promote N conservation and increase the Y of facility agriculture crops.

Polyamine Metabolism in Scots Pine Embryogenic Cells under Potassium Deficiency

Polyamines (PA) have a protective role in maintaining growth and development in Scots pine during abiotic stresses. In the present study, a controlled liquid Scots pine embryogenic cell culture was used for studying the responses of PA metabolism related to potassium deficiency. The transcription level regulation of PA metabolism led to the accumulation of putrescine (Put). Arginine decarboxylase (ADC) had an increased expression trend under potassium deficiency, whereas spermidine synthase (SPDS) expression decreased. Generally, free spermidine (Spd) and spermine (Spm)/ thermospermine (t-Spm) contents were kept relatively stable, mostly by the downregulation of polyamine oxidase (PAO) expression. The low potassium contents in the culture medium decreased the potassium content of the cells, which inhibited cell mass growth, but did not affect cell viability. The reduced growth was probably caused by repressed metabolic activity and cell division, whereas there were no signs of H₂O₂-induced oxidative stress or increased cell death. The low intracellular content of K⁺ decreased the content of Na⁺. The decrease in the pH of the culture medium indicated that H⁺ ions were pumped out of the cells. Altogether, our findings emphasize the specific role(s) of Put under potassium deficiency and strict developmental regulation of PA metabolism in Scots pine.