Phosphorus and nitrogen interaction: loss of QC identity in response to P or N limitation is antecipated in pdr23 mutant

Water Polishing improved controlled-release characteristics and fertilizer efficiency of castor oil-based polyurethane coated diammonium phosphate

The production cost of controlled-release fertilizers is an important factoring limiting their applications. To reduce the coating cost of diammonium phosphate (DAP) and improve its nutrition release characteristics, the fertilizer cores were modified by water polishing with three dosages at 1, 2, and 3%. The effects of modification were evaluated in terms of particle hardness, size distribution, angle of repose and specific surface area. Castor oil-based polyurethane was used as coating material for fertilizer performance evaluation. A pot experiment was conducted to verify the fertilizer efficiency of coated diammonium phosphate (CDAP) with maize. The results showed that polishing with 2% water reduced the angle of repose by 2.48-10.57% and specific surface area by 5.70-48.76%, making it more suitable for coating. The nutrient release period of CDAP was significantly prolonged by 5.36 times. Soil available phosphorous, enzyme activities, maize grain yield, and phosphorous use efficiency were all improved through the blending application of coated and normal phosphate fertilizer. This study demonstrated that water-based surface modification is a low-cost and effective method for improvement and promotion of controlled release P fertilizers.

miRNA778 and SUVH6 are involved in phosphate homeostasis in Arabidopsis

microRNAs (miRNAs) play an important role in plant adaptation to phosphate (Pi) starvation. Histone methylation can remodel chromatin structure and mediate gene expression. This study identified Arabidopsis miR778, a Pi-responsive miRNA, and its target gene Su(var) 3-9 homologs 6 (SUVH6) encoding a histone H3 lysine 9 (H3K9) methyltransferase. Overexpression of miR778 moderately enhanced primary and lateral root growth, free phosphate accumulation in shoots, and accumulation of anthocyanin under Pi deficient conditions. miR778 overexpression relieved the arrest of columella cell development under Pi starvation. Conversely, transgenic plants overexpressing a miR778-target mimic (35S::MIM778), that act as a sponge and sequesters miR778, showed opposite phenotypes of 35S::miR778 plants under Pi deficiency. Expression of several Pi deficiency-responsive genes such as miR399, Phosphate Transporter (PHT1;4), Low Phosphate-Resistant1 (LPR1) and Production of Anthocyanin Pigment 1 (PAP1) were elevated in the miR778 overexpressing plants, suggesting that both miR778 and SUVH6 are involved in phosphate homeostasis in plants. This study has provided a basis for further investigation on how SUVH6 regulates its downstream genes through chromatin remodeling and DNA methylation in plants stressed by Pi deficiency.

Form matters: morphological aspects of lateral root development

BACKGROUND

The crucial role of roots in plant nutrition, and consequently in plant productivity, is a strong motivation to study the growth and functioning of various aspects of the root system. Numerous studies on lateral roots, as a major determinant of the root system architecture, mostly focus on the physiological and molecular bases of developmental processes. Unfortunately, little attention is paid either to the morphological changes accompanying the formation of a lateral root or to morphological defects occurring in lateral root primordia. The latter are observed in some mutants and occasionally in wild-type plants, but may also result from application of external factors.

SCOPE AND CONCLUSIONS

In this review various morphological aspects of lateral branching in roots are analysed. Morphological events occurring during the formation of a typical lateral root are described. This process involves dramatic changes in the geometry of the developing organ that at early stages are associated with oblique cell divisions, leading to breaking of the symmetry of the cell pattern. Several types of defects in the morphology of primordia are indicated and described. Computer simulations show that some of these defects may result from an unstable field of growth rates. Significant changes in both primary and lateral root morphology may also be a consequence of various mutations, some of which are auxin-related. Examples reported in the literature are considered. Finally, lateral root formation is discussed in terms of mechanics. In this approach the primordium is considered as a physical object undergoing deformation and is characterized by specific mechanical properties.

Nitrogen and phosphorus interaction and cytokinin: responses of the primary root of Arabidopsis thaliana and the pdr1 mutant

Nitrogen (N) and phosphorus (P) are the two most limiting nutrients for plant yield. Plants modify their metabolism and growth to cope with resources availability, consequently the integration of diverse signals is required. There is mounting evidence of N and P interaction, however, the sharing components of their signaling pathways have not been revealed yet. The pdr1 mutant has proved potentially useful in understanding the responses to nitrate (Ni), P and cytokinin. The mutation conferred pdr1 reduced root length in response to Ni under P deficiency and no effect of low cytokinin concentration. High N availability and high cytokinin caused strong root growth inhibition by different paths in wild type. Cytokinin repressed cell division, exhausted the quiescent center, caused changes in the pattern of AtPT1 expression and reduced AtACP5 expression. On the contrary, high N induced cell division as well as increased the expression of AtPT1 and AtACP5 even at high P availability. The data indicated interaction in the root modulation by N and P; and PDR1 is probably a signaling component of the nutritional status in Arabidopsis thaliana that modulates the response to N and P only partially mediated by cytokinin.