The results suggest that although root hair length is not important for maintaining yield, the presence of root hairs is implicit to sustainable yield of barley under P-deficient conditions and when combined with extreme drought. Root hairs are a trait that should be maintained in future germplasm.

Summary Two experiments have investigated the persistence of 16 arable, annual broad‐leaved weed species over 6 years in a silty loam and a clay soil. Small plastic beads were included as an ‘inert’ comparison. Seeds were broadcast in October on to plots at the start of the experiment, and these were either tine cultivated or ploughed annually thereafter. Plots were sown with either spring or winter wheat. As far as possible, weed seeding was prevented each year. For some species, the seed decline appeared to be slower on the ploughed plots than on the tined plots and in the winter wheat compared with the spring wheat. Seed decline also tended to be slower on the clay soil at Rothamsted than on the silty loam at Long Ashton. Some species declined rapidly (e.g. Brassica napus, Chrysanthemum segetum, Galium aparine, Galeopsis tetrahit), with annual decline rates in excess of 58%, whereas others declined very little (e.g. Papaver rhoeas decline rate 9%). Most of the other species had decline rates between 20% and 40%. The results are discussed in relation to the development of population dynamics models to predict long‐term consequences of alternative weed management strategies.

SummarySpecies diversity and abundance in weed seedbanks were measured at the beginning, and after 3 and 6 yr of the TALISMAN experiment at ADAS Boxworth, Drayton and High Mowthorpe. Fifty species were distinguished in the seedbanks of treatments comprising winter and spring rotations and full and reduced herbicide input. After 6 yr, the number of seedbank species in the main treatments ranged from 11 in the most intense to 26 in the least intense management. Principal co‐ordinate analysis showed that the seedbank community diverged over time between sites and additionally between the two rotation treatments at Boxworth. Only four species were common to all sites but community‐scale descriptors indicated that the change in seedbanks following reduced inputs had common features at the three sites. First, species‐area relations showed a greater relative increase in number of taxa at a plot scale than in the site as a whole, indicating lower inputs encouraged the common weeds more than rare species. Second, both the mean and the standard deviation of the species‐abundance distribution at 6 yr increased in response to reduced inputs. As a result, the number of species slightly more than doubled as herbicide units were reduced from four to one while the total number of seeds increased by two orders of magnitude. Some causes of seedbank change were identified: spring‐germinating species tended to increase when spring cultivation was common in the rotation, while some competitive weeds had a relatively low abundance when they were targeted by herbicide. The results are discussed in relation to optimising the various functions of the seedbank.

No abstract

Many humans lack sufficient zinc (Zn) in their diet for their wellbeing and increasing Zn concentrations in edible produce (biofortification) can mitigate this. Recent efforts have focused on biofortifying staple crops. However, greater Zn concentrations can be achieved in leafy vegetables than in fruits, seeds, or tubers. Brassicas, such as cabbage and broccoli, are widely consumed and might provide an additional means to increase dietary Zn intake. Zinc concentrations in brassicas are limited primarily by Zn phytotoxicity. To assess the limits of Zn biofortification of brassicas, the Zn concentration in a peat:sand (v/v 75:25) medium was manipulated to examine the relationship between shoot Zn concentration and shoot dry weight (DW) and thereby determine the critical shoot Zn concentrations, defined as the shoot Zn concentration at which yield is reduced below 90%. The critical shoot Zn concentration was regarded as the commercial limit to Zn biofortification. Experiments were undertaken over six successive years. A linear relationship between Zn fertiliser application and shoot Zn concentration was observed at low application rates. Critical shoot Zn concentrations ranged from 0.074 to 1.201 mg Zn g −1 DW among cabbage genotypes studied in 2014, and between 0.117 and 1.666 mg Zn g −1 DW among broccoli genotypes studied in 2015-2017. It is concluded that if 5% of the dietary Zn intake of a population is currently delivered through brassicas, then the biofortification of brassicas from 0.057 to > 0.100 mg Zn g −1 DW through the application of Zn fertilisers could increase dietary Zn intake substantially.

Summary The prevalence of sodium (Na)‐‘hyperaccumulator’ species, which exhibit abnormally large shoot sodium concentrations ([Na]shoot) when grown in nonsaline environments, was investigated among angiosperms in general and within the Caryophyllales order in particular.Shoot Na concentrations were determined in 334 angiosperm species, representing 35 orders, grown hydroponically in a nonsaline solution.Many Caryophyllales species exhibited abnormally large [Na]shoot when grown hydroponically in a nonsaline solution. The bimodal distribution of the log‐normal [Na]shoot of species within the Caryophyllales suggested at least two distinct [Na]shoot phenotypes within this order. Mapping the trait of Na‐hyperaccumulation onto the phylogenetic relationships between Caryophyllales families, and between subfamilies within the Amaranthaceae, suggested that the trait evolved several times within this order: in an ancestor of the Aizoaceae, but not the Phytolaccaceae or Nyctaginaceae, in ancestors of several lineages formerly classified as Chenopodiaceae, but not in the Amaranthaceae sensu stricto, and in ancestors of species within the Cactaceae, Portulacaceae, Plumbaginaceae, Tamaricaceae and Polygonaceae.In conclusion, a disproportionate number of Caryophyllales species behave as Na‐hyperaccumulators, and multiple evolutionary origins of this trait can be identified within this order.

White oak (Quercusalba L.) seedlings grown in a silt loam soil inoculated with Pisolithustinctorius (Pers.) Coker and Couch exhibited 80% ectomycorrhizal development after a 6-month establishment period whereas the noninoculated controls exhibited less than 5%.When water was withheld and soil water potential decreased as the soil dried, xylem pressure potential and leaf conductance of both the inoculated and noninoculated seedlings declined gradually. At the peak of the drying cycle, the inoculated seedlings exhibited mean prelight and midlight xylem pressure potential values which were 0.2 MPa and 0.15 MPa, respectively, more negative than the noninoculated seedlings. Although the inoculated seedlings had a mean leaf surface area 1.5 times larger than that of the noninoculated seedlings, there were no significant differences in leaf conductance at the peak of the dehydration cycle. Mean rates of root elongation were greater among the inoculated seedlings during the drying cycle. Following reirrigation of the soil, the inoculated seedlings yielded significantly less negative values of prelight and midlight xylem pressure potential and greater leaf conductance when compared to the noninoculated seedlings.

Insufficient calcium (Ca) or magnesium (Mg) in the diets of humans and animals has negative effects on health. Knowledge of the concentrations of Ca and Mg in edible crops can help inform the formulation of appropriate diets. There are large differences in shoot concentrations of both Ca ([Ca]shoot) and Mg ([Mg]shoot) between angiosperm orders. For example, relative to other angiosperms, commelinid monocot species generally have lower [Ca]shoot and [Mg]shoot; species from the Cucurbitales, Malvales and Brassicales generally have higher [Ca]shoot and [Mg]shoot; and species from the Oxalidales and Caryophyllales generally have higher [Mg]shoot but similar [Ca]shoot, which results in higher [Mg]shoot/[Ca]shoot quotients. In this paper the evolution of the combined traits of high [Mg]shoot and high [Mg]shoot/[Ca]shoot quotient in the Caryophyllales was resolved at the family level. All Caryophyllales families had high mean [Mg]shoot and [Mg]shoot/[Ca]shoot quotients, suggesting that both of these traits evolved in an ancient ancestor of all Caryophyllales families.