Plant nutrition--roots of life for fundamental biology and better crop production

Use of a mobile plant identification application and the out-of-school learning method in biodiversity education

Today, many students are no longer able to identify plants and researchers use the term "plant blindness" to describe students' ignorance of plant species. Knowledge of plant species is among the factors that best support an interest in and understanding of environmental issues, biodiversity, and a sustainable lifestyle. With the help of mobile technologies, it is thought that the knowledge level of students about herb and tree varieties can be increased outside of class hours and in outdoor education. The aim of this study was to determine the effect of the use of the PlantNet mobile application and the out-of-school learning method on the knowledge levels of 5th-grade students about the plant species in their environment and their behaviors demonstrating an understanding of biodiversity. For this purpose, at the beginning of the study, a plant species questionnaire and a biodiversity behavior questionnaire were applied to the students. Afterward, the students were asked to examine the plant species around them using the PlantNet mobile application. At the end of the activities, the data collection tools applied at the beginning of the study were applied again. It was determined that the students who participated in the activities displayed more biodiversity-related behaviors than before they participated in the activities, and that the students were able to write down more herb and tree species at the end of the activities. In addition, as a result of the activities, a positive and high-level relationship was found between the students' biodiversity-related behaviors and the total number of plant species they knew.

Evaluation of seed nitrate assimilation and stimulation of phenolic-linked antioxidant on pentose phosphate pathway and nitrate reduction in three feed-plant species

BACKGROUND

Soil and water pollution due to nitrate are becoming increasingly serious worldwide. The government also put forward relevant governance policies, and a large number of scholars studied chemical physics and other methods to remove nitrate in water, but the cost was substantial. Studies have found that planting systems including grasses have the potential to remove nitrates. However, there are few studies on nitrate linked pathway and nitrate assimilation during its early growth.

RESULTS

We have evaluated three different feed-plant species with three levels of overnight seed nitrate treatments along with a control. The activity of different enzymes from 2 weeks old shoots was measured to get a comprehension of proline-associated pentose phosphate pathway coupled with nitrate assimilation and phenolic-linked antioxidant response system in these species under nitrate treatments. All three feed-plant species showed high nitrate tolerance during germination and early growth stages. It is perceived that the accumulation of total soluble phenolics and total antioxidant activity was high in all three feed-plant species under high nitrate treatments. In terms of high G6PDH activity along with low SDH activity in alfalfa, there may be a shift of carbon flux in this species under high nitrate treatments. Higher activity of these enzymes along with higher SOD and GPX activity was observed in alfalfa. The efficient mechanism of nitrate stress tolerance of alfalfa also correlated with higher photochemical efficiency. Perennial ryegrass also showed excellent potential under high nitrate treatments by adopting an efficient mechanism to counter nitrate-induced oxidative stress.

CONCLUSIONS

Under the condition of nitrate treatment, the germination rates of the three feed-plant species are still ideal, and they have good enzyme activity and have the potential to remove nitrate.

Nitrogen-regulated changes in total amino acid profile of maize genotypes having contrasting response to nitrogen deficit

Sustainable development of cellular organisms depends on a precise coordination between the carbon and nitrogen metabolisms within the living system. Inorganic N is assimilated into amino acids which serve as an important N source for various regulatory metabolic pathways in plants. This study investigates the role of amino acids in C/N balance by examining changes in amino acid profile in the leaves and roots of low-N-tolerant (PHEM-2) and low-N-sensitive (HM-4) maize genotypes grown hydroponically under N-sufficient (4.5 mM), N-deficient (0.05 mM) and N-restoration conditions. N application effectively altered the level of cysteine, methionine, asparagine, arginine, phenylalanine, glycine, glutamine, aspartate and glutamate in both genotypes. Under low N (0.05 mM), the asparagine and glutamine contents increased, while those of glutamate, phenylalanine and aspartate decreased in both genotypes. However, serine content increased in PHEM-2 but decreased in HM-4. Resupply of N to low-N-grown plants of both genotypes restored the amino acids level to that in the control; the restoration was quicker and more consistent in PHEM-2 than in HM-4. Based on alteration of amino acid level, a strategy can be developed to improve the ability of maize to adapt to low-N environments by way of an improved N utilization.

Sulfur starvation and restoration affect nitrate uptake and assimilation in rapeseed

We analyzed the effect of omission of sulfur (S) from the nutrient solution and then restoration of S-source on the uptake and assimilation of nitrate in rapeseed. Incubation in nutrient solution without S for 1-6 days led to decline in uptake of nitrate, activities, and expression levels of nitrate reductase (NR) and glutamine synthetase (GS). The nitrite reductase (NiR) and glutamate synthase (GOGAT) activities were not considerably affected. There was significant enhancement in nitrate content and decline in sulfate content. Evaluation of amino acid profile under S-starvation conditions showed two- to fourfold enhancement in the contents of arginine, asparagine and O-acetyl-L-serine (OAS), whereas the contents of cysteine and methionine were reduced heavily. When the S-starved plants were subjected to restoration of S for 1, 3, 5, and 7 days, activities and expression levels of NR and GS recovered within the fifth and seventh days of restoration, respectively. Exogenous supply of metabolites (arginine, asparagine, cysteine, glutamine, OAS, and methionine) also affected the uptake and assimilation of nitrate, with a maximum for OAS. These results corroborate the tight interconnection of S-nutrition with nitrate assimilation and that OAS plays a major role in this regulation. The study must be helpful in developing a nutrient-management technology for optimization of crop productivity.