1. Plant Nutrients. 2. The Soil as a Plant Nutrient Medium. 3. Nutrient Uptake and Assimilation. 4. Plant Water Relationships. 5. Plant Growth and Crop Production. 6. Fertilizer Application. 7. Nitrogen. 8. Sulphur. 9. Phosphorus. 10. Potassium. 11. Calcium. 12. Magnesium. 13. Iron. 14. Manganese. 15. Zinc. 16. Copper. 17. Molybdenum. 18. Boron. 19. Further Elements of Importance. 20. Elements with More Toxic Effects. General Readings. References. Index.

/pdf/principles-of-plant-nutrition-2k4wl46ou6.pdf

Principles of plant nutrition

https://www.cell.com/trends/plant-science/pdf/S1360-1385(09)00298-2.pdf

Proline: a multifunctional amino acid

Jasmonic acid and its derivatives can modulate aspects of fruit ripening, production of viable pollen, root growth, tendril coiling, and plant resistance to insects and pathogens. Jasmonate activates genes involved in pathogen and insect resistance, and genes encoding vegetative storage proteins, but represses genes encoding proteins involved in photosynthesis. Jasmonic acid is derived from linolenic acid, and most of the enzymes in the biosynthetic pathway have been extensively characterized. Modulation of lipoxygenase and allene oxide synthase gene expression in transgenic plants raises new questions about the compartmentation of the biosynthetic pathway and its regulation. The activation of jasmonic acid biosynthesis by cell wall elicitors, the peptide systemin, and other compounds will be related to the function of jasmonates in plants. Jasmonate modulates gene expression at the level of translation, RNA processing, and transcription. Promoter elements that mediate responses to jasmonate have been isolated. This review covers recent advances in our understanding of how jasmonate biosynthesis is regulated and relates this information to knowledge of jasmonate modulated gene expression.

Biosynthesis and action of jasmonates in plants

Summary
The diets of over two-thirds of the world's population lack one or more essential mineral elements. This can be remedied through dietary diversification, mineral supplementation, food fortification, or increasing the concentrations and/or bioavailability of mineral elements in produce (biofortification). This article reviews aspects of soil science, plant physiology and genetics underpinning crop biofortification strategies, as well as agronomic and genetic approaches currently taken to biofortify food crops with the mineral elements most commonly lacking in human diets: iron (Fe), zinc (Zn), copper (Cu), calcium (Ca), magnesium (Mg), iodine (I) and selenium (Se). Two complementary approaches have been successfully adopted to increase the concentrations of bioavailable mineral elements in food crops. First, agronomic approaches optimizing the application of mineral fertilizers and/or improving the solubilization and mobilization of mineral elements in the soil have been implemented. Secondly, crops have been developed with: increased abilities to acquire mineral elements and accumulate them in edible tissues; increased concentrations of ‘promoter’ substances, such as ascorbate, β-carotene and cysteine-rich polypeptides which stimulate the absorption of essential mineral elements by the gut; and reduced concentrations of ‘antinutrients’, such as oxalate, polyphenolics or phytate, which interfere with their absorption. These approaches are addressing mineral malnutrition in humans globally.

/pdf/biofortification-of-crops-with-seven-mineral-elements-often-3g2xc3trnk.pdf

Biofortification of crops with seven mineral elements often lacking in human diets--iron, zinc, copper, calcium, magnesium, selenium and iodine.

Short protocols in molecular biology

THE ROOT EPIDERMIS IS COMPOSED OF TWO CELL TYPES: trichoblasts (or hair cells) and atrichoblasts (or non-hair cells). In lettuce (Lactuca sativa cv. Grand Rapids var. Rapidmor oscura) plants grown hydroponically in water, the root epidermis did not form root hairs. The addition of 10 microM sodium nitroprusside (SNP), a nitric oxide (NO) donor, resulted in almost all rhizodermal cells differentiated into root hairs. Treatment with the synthetic auxin 1-naphthyl acetic acid (NAA) displayed a significant increase of root hair formation (RHF) that was prevented by the specific NO scavenger carboxy-PTIO (cPTIO). In Arabidopsis, two mutants have been shown to be defective in NO production and to display altered phenotypes in which NO is implicated. Arabidopsis nos1 has a mutation in an NO synthase structural gene (NOS1), and the nia1 nia2 double mutant is null for nitrate reductase (NR) activity. We observed that both mutants were affected in their capacity of developing root hairs. Root hair elongation was significantly reduced in nos1 and nia1 nia2 mutants as well as in cPTIO-treated wild type plants. A correlation was found between endogenous NO level in roots detected by the fluorescent probe DAF-FM DA and RHF. In Arabidopsis, as well as in lettuce, cPTIO blocked the NAA-induced root hair elongation. Taken together, these results indicate that: (1) NO is a critical molecule in the process leading to RHF and (2) NO is involved in the auxin-signaling cascade leading to RHF.

https://www.tandfonline.com/doi/pdf/10.4161/psb.1.1.2398

Nitric oxide functions as a positive regulator of root hair development.

In Arabidopsis thaliana, urease transcript levels increased sharply between 2 and 4 d after germination (DAG) and were maintained at maximal levels until at least 8 DAG. Seed urease specific activity declined upon germination but began to increase in seedlings 2 DAG, reaching approximately 75% of seed activity by 8 DAG. Urea levels showed a small transient increase 1 DAG and then approximately paralleled urease activity, reaching maximal levels at approximately 9 DAG. Urease inhibition with phenylphosphorodiamidate resulted in a 2- to 4-fold increase in urea levels throughout seedling development. Arginine pools (0-8 DAG) changed approximately in parallel with the urea pool. Consistent with arginine being a major source of urea, arginase activity increased 10-fold in the interval 0 to 6 DAG. Allopurinol, a xanthine dehydrogenase inhibitor, had no effect on urea levels up to 3 DAG but reduced the urea pool by 30 to 40% during the interval 5 to 8 DAG, suggesting that purine degradation contributed to the urea pool well after germination, if at all. in aged Arabidopsis seeds, there was correlation between phenylphosphorodiamidate inactivation of urease and germination inhibition, the latter overcome by NH4NO3 or amino acids. Since urease activity, urea precursor, and urea increase in young seedlings, and since urease inactivation results in a nitrogen-reversible inhibition of germination, we propose that urease recycles urea-nitrogen in the seedling.

Essential Role of Urease in Germination of Nitrogen-Limited Arabidopsis thaliana Seeds

Mutation of either arginase structural gene (ARGAH1 or ARGAH2 encoding arginine [Arg] amidohydrolase-1 and -2, respectively) resulted in increased formation of lateral and adventitious roots in Arabidopsis (Arabidopsis thaliana) seedlings and increased nitric oxide (NO) accumulation and efflux, detected by the fluorogenic traps 3-amino,4-aminomethyl-2′,7′-difluorofluorescein diacetate and diamino-rhodamine-4M, respectively. Upon seedling exposure to the synthetic auxin naphthaleneacetic acid, NO accumulation was differentially enhanced in argah1-1 and argah2-1 compared with the wild type. In all genotypes, much 3-amino,4-aminomethyl-2′,7′-difluorofluorescein diacetate fluorescence originated from mitochondria. The arginases are both localized to the mitochondrial matrix and closely related. However, their expression levels and patterns differ: ARGAH1 encoded the minor activity, and ARGAH1-driven β-glucuronidase (GUS) was expressed throughout the seedling; the ARGAH2∷GUS expression pattern was more localized. Naphthaleneacetic acid increased seedling lateral root numbers (total lateral roots per primary root) in the mutants to twice the number in the wild type, consistent with increased internal NO leading to enhanced auxin signaling in roots. In agreement, argah1-1 and argah2-1 showed increased expression of the auxin-responsive reporter DR5∷GUS in root tips, emerging lateral roots, and hypocotyls. We propose that Arg, or an Arg derivative, is a potential NO source and that reduced arginase activity in the mutants results in greater conversion of Arg to NO, thereby potentiating auxin action in roots. This model is supported by supplemental Arg induction of adventitious roots and increased NO accumulation in argah1-1 and argah2-1 versus the wild type.

https://www.jstor.org/stable/info/40066129

Arginase-Negative Mutants of Arabidopsis Exhibit Increased Nitric Oxide Signaling in Root Development

Ni is the most recent candidate to be added to the list of 13 essential mineral elements for higher plants although failure to complete the life cycle in the absence of Ni has only been demonstrated in a few plant species. Ni is considered an essential element primarily because of its function as an irreplaceable component of urease which is responsible for the hydrolysis of urea N, and which seems to be the only proven nutritional function of Ni in higher plants. For production of full urease activity and growth on urea N a critical deficiency level of around 100 μg kg—1 DW seems appropriate, while plants depending on mineral N may have a lower Ni requirement. Ni has also other effects on plant growth, of which the phytosanitary action is possibly most significant in the field. The incorporation of Ni into urease apoprotein requires the active participation of several accessory proteins, and mutations in genes coding the accessory proteins as well as the urease apoprotein have been exploited to characterise aspects of urease activation. The mobility of Ni within the plant, as compared to other heavy metals, is usually high, although little is known of the uptake mechanisms and the form of transported Ni under Ni-deprived conditions. This as well as other effects of Ni that cannot be related to its structural component of urease, remain to be elucidated.



Die Bedeutung von Nickel fur das Wachstum und den Stoffwechsel von Pflanzen



Ni ist der jungste Kandidat fur die Liste der bisher 13 essentiellen mineralischen Nahrelemente hoherer Pflanzen, obwohl der Beweis fur seine Notwendigkeit zur Vollendung des Lebenszyklus einer Pflanze erst bei wenigen Arten gelang. Die Essentialitat von Ni begrundet sich insbesondere auf dessen Funktion als unersetzlicher Bestandteil des Enzyms Urease, welches die Hydrolyse von Harnstoff katalysiert. Dies ist die bislang einzige nachgewiesene Funktion von Ni in der hoheren Pflanze. Hinsichtlich des Wachstums harnstoffernahrter Pflanzen und der Ureaseaktivitat konnte ein kritischer Gehalt von etwa 100 μg kg—1 TM abgeleitet werden, wahrend Pflanzen, die mineralischen N erhalten, einen wesentlich geringeren Ni-Bedarf haben. Ni hat noch weitere Effekte auf das Pflanzenwachstum, von denen die phytosanitaren Wirkungen unter Feldbedingungen sicherlich die wichtigsten sind. Der Einbau von Ni in die Ureaseapoproteine erfordert die aktive Beteiligung mehrerer akzessorischer Proteine und Mutationen der Gene, die diese akzessorischen Proteine und die Ureasestrukturgene kodieren, wurden erfolgreich zur Aufklarung zahlreicher Aspekte der Ureaseaktivierung eingesetzt. Die innerpflanzliche Mobilitat von Ni ist, verglichen mit anderen Schwermetallen, normalerweise relativ hoch, doch liegen nur wenige Informationen uber die Ni-Aufnahme und transportierten Ni-Spezies bei niedrigem Ni-Angebot vor. Diese und andere Aspekte der Ni-Ernahrung, die nicht auf dessen strukturelle Bedeutung in der Urease zuruckgefuhrt werden konnen, harren ihrer Untersuchung.

Significance of nickel for plant growth and metabolism

Publisher Summary This chapter discusses the role of urease in plant cells Urease is important for efficient nitrogen assimilation Considerable amounts of plant nitrogen flow through urea (urease substrate), which can be recycled only by urease action This recapture can have significant quality impact on protein rich crops It appears to have an important role in germination of protein poor seeds The urease substrate urea is derived from arginine and ureides Arginine is the richest nitrogen repository among the amino acids of seed storage proteins On the other hand, ureides are not only significant sources of nitrogen in nucleic acid turnover but are also a predominant transport from of fixed nitrogen in soybean and other tropical legumes Urease-negative plants accumulate substantial, nonutilizable urea in both maternal and embryonic tissue During germination of urease-negative seeds, further urea accumulates as a dead end in nitrogen metabolism Abundant seed ureases, such as, Sumner's jackbean urease, may play a chemical defense role All of the ureases, both from bacteria and plants, resemble each other in primary structure and in their requirement for accessory genes

Joseph C. Polacco

Papers

Nitric oxide functions as a positive regulator of root hair development.

Essential Role of Urease in Germination of Nitrogen-Limited Arabidopsis thaliana Seeds

Arginase-Negative Mutants of Arabidopsis Exhibit Increased Nitric Oxide Signaling in Root Development

Significance of nickel for plant growth and metabolism

Roles of urease in plant cells