While lateral roots comprise the bulk of root length, axial roots function as a scaffold determining the distribution of these laterals.
Continue reading Soil compaction and nitrate capture
New research finds that root capturing more nutrients could help wildlife breathe many miles away.
Continue reading Improving roots for crops could improve habitats for wildlife
Seed germination is a critical step in the life cycle of flowering plants. Since seeds contain limited reserves, seed germination has to be tightly regulated to ensure that germination takes place in a suitable environment where seedlings can reach the sunlight and carry out photosynthesis before seed reserves are exhausted. However, seeds may not be able to germinate even under favorable conditions, which is called seed dormancy. Huai-Syuan Ciou and colleagues tested to see if a plastid J-domain protein DJC75/CRRJ in Arabidopsis (Arabidopsis thaliana) is important for nitrate-promoted seed germination in the dark. The ability of nitrate to stimulate seed...
Continue reading A key protein may help trigger germination in Arabidopsis seeds
Most plants acquire nitrogen from the soil in the form of nitrate (NO3−) or ammonium (NH4+). Ammonium-based nutrition is gaining interest because it helps to avoid environmental concerns associated with nitrate fertilisation. The two main issues with nitrate-based fertilisers are the leaching of excess fertiliser into water courses and the formation of nitrous oxide, a powerful greenhouses gas, that contributes to global warming. Ammonium-based fertilisers are useful in mitigating some of these unwanted environmental effects. Unfortunately, plants tend to respond less to ammonium compared to nitrate fertilisation. A recent study by de la Peña et al. and published in AoBP proposes...
Continue reading The suitability of Brachypodium distachyon for the study of ammonium stress in cereals
Plants take up and assimilate nitrogen (N) in the form of nitrate (NO3–) or ammonium (NH4+), or a combination of both. When oxygen availability is reduced (hypoxia), plants need to generate energy to survive and protect themselves against the hypoxia-induced damage. Wany et al. investigate the role of NO3– or NH4+ on increasing energy efficiency under hypoxia in Arabidopsis. They find that hypoxic stress under NO3– nutrition leads to increased nitrate reductase activity, nitric oxide (NO) production, class 1 phytoglobin gene expression, and in turn ATP production. These effects were reduced under NH4+ nutrition. The results indicate that NO3–nutrition influences multiple factors in order to increase...
Continue reading Nitrate nutrition improves energy efficiency under hypoxic stress
Rangarajan et al. employ the functional–structural model SimRoot to explore how interactions among architectural phenes in common bean, Phaseolus vulgaris (Fabaceae) determine the acquisition of phosphate and nitrate, two key soil resources contrasting in mobility. The utility of a root architectural phenotype is determined by whether the constituent phenes are synergistic or antagonistic. Competition for internal resources and trade-offs for external resources result in multiple phenotypes being optimal under a given nutrient regime. No single phenotype is optimal across contrasting environments. These results have implications for understanding plant evolution and also for the breeding of more stress-tolerant crop phenotypes.
Continue reading Phene interactions determine nutrient capture in common bean
Plant regrowth in response to defoliation relies on efficient nitrogen use. Roche et al. find that remobilisation of water soluble carbohydrate stores in leaves of perennial ryegrass (Lolium perenne) is coordinated with nitrogen availability to support efficient N assimilation into amino acids in leaf and sheath tissues. Spatiotemporal changes in cytokinin content in response to changes in the internal carbon-nitrogen balance indicate that cytokinins could act as a mobile signal between below- and above- ground tissues in response to defoliation.
Continue reading Carbon stores support efficient nitrate use during regrowth of perennial ryegrass
Plants need nitrogen (N) for growth, development and defence against abiotic and biotic stresses. The widespread use of artificial N fertilisers and the agricultural impact of N nutrition on disease development have been extensively examined. In this review article, Mur et al. show that NO3– or NH4+ fertilisers affect the outcome of plant–pathogen interactions. They find NO3– feeding augments hypersensitive response (HR) mediated resistance, whilst ammonium nutrition can compromise defence. Metabolically, NO3– enhances production of polyamines such as spermine and spermidine defence signals, whilst NH4+ nutrition leads to increased γ-aminobutyric acid (GABA) levels which may be a nutrient source for...
Continue reading The role of nitrogen in plant defence
Additional carbohydrate supply resulting from enhanced photosynthesis under predicted future elevated CO2 is likely to increase symbiotic nitrogen fixation in legumes. Butterly et al. use free-air CO2 enrichment (FACE) to study field pea, Pisum sativum, growing under different levels of CO2 and N supply in a semi-arid cropping system and find that increasing N reduces nodulation at ambient CO2 but this inhibitory effect is less under elevated CO2. The results indicate that field pea may perform well in semi-arid agricultural systems under future CO2 concentrations irrespective of soil N status and subsequent gains in N input via enhanced N2 fixation...
Continue reading Elevated CO2 reduces nitrate inhibition of N2 fixation in Pisum
Silicon (Si) is important in mitigating abiotic and biotic plant stresses, yet many agricultural soils, such as those of the rainfed production areas of the South African sugar industry, are deficient in plant-available Si, making Si supplementation necessary. Means to maximise Si uptake via the roots from applied silicon sources and thereby enhance crop yields have not yet been fully explored. In a new study published in AoB PLANTS, Keeping et al. found that reduction of rhizosphere pH through provision of nitrogen fertilizer to sugarcane as ammonium rather than nitrate increased silicon uptake from a low-silicon soil amended with calcium...
Continue reading Provision of nitrogen as ammonium rather than nitrate increases silicon uptake in sugarcane
Using a thermodynamic flow–force interpretation of nitrate uptake isotherms, Malagoli and Le Deunff develop a functional– structural model to predict N uptake in winter oilseed rape, Brassica napus. The structural component of the model, the active root biomass, is derived from a combination of root mapping in the field, the relationship between specific root length and external nitrate concentration, and the assignment of an absorption capacity related to integrated root system age. They find that model simulations are well matched to measured data for N uptake under field conditions at three different levels of fertilizer application. Model ouputs indicate that...
Continue reading Nitrate uptake modelling in plants: root activity
The influence of light on germination was much stronger in smaller than in larger seeds.
Continue reading Why small seeds require light to germinate
A study of rice cultivars with differing responsiveness to nitrate finds that initiation of lateral roots is only enhanced with higher responsiveness.
Continue reading Auxin distribution and nitrate in rice roots
Plants can utilize two major forms of inorganic nitrogen, nitrate (NO3–) and ammonium (NH4+), with some species appearing to ‘prefer’ one form over another, under certain conditions. Soil-N speciation has been shown to be an important determinant of species distribution, but no ecophysiologically realistic, mathematically sound model has yet emerged to describe and predict this phenomenon. In a viewpoint article in Annals of Botany, Britto and Kronzucker suggest that this is because assignment of such preferences is not straightforward, and must take into account a wide array of complex physiological and environmental features, which interact in ways that are still...
Continue reading N-source preference in plants (Viewpoint)Botany One is a blog run by the Annals of Botany Company, a non-profit educational charity.
In addition to Botany One, the company currently publishes three journals, the Annals of Botany, AoB PLANTS, and in silico Plants.
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