Soil alkalinity imposes important limitations to lupin productivity; however, little attention has been paid to investigate the effects of soil alkalinity on plant growth and development. Many lupins are sensitive to alkaline soils, but Lupinus albus material from Egypt was found to have tolerance to limed soils. The aim of this study was to compare the growth response of two cultivars of L.albus L. – an Egyptian cultivar, P27734, and an Australian cultivar, Kiev Mutant, to different soil pH levels and to understand the physiological mechanisms underlying agronomic alkalinity tolerance of P27734. Plants were grown under three pH levels (5.1, 6.7, and 7.8) in a temperature-controlled glasshouse. For both cultivars, the greatest dry mass production and carboxylate exudation from roots were observed at alkaline pH. The better performance of the Egyptian cultivar at high pH was entirely accounted for by its greater seed weight. From a physiological perspective, the Australian cultivar was as alkaline-tolerant as the Egyptian cultivar. These findings highlight the agronomic importance of seed weight for sowing, and both cultivars can be used in alkaline soils.

Drought is the major abiotic constraint to the rice production in the rain-fed areas across Asia and sub-Saharan Africa. Wild species of Oryza offer a wide spectrum of adaptive traits and can serve as potential donors of biotic and abiotic stress tolerance. At the Punjab Agricultural University, we are maintaining an active collection of 1630 accessions of wild species germplasm (AA, CC, BBCC and CCDD) of rice. These accessions were screened to assess genetic variation for drought tolerance under field conditions. Severe water stress was imposed at the late vegetative stage by withholding water initially for 25 d and then extended further to 35 d during kharif season in the years 2013–14 and 2015–16. The tolerance score for drought stress was based on the extent of leaf rolling and leaf drying. Based on the 2 years’ data, seven accessions from Oryza rufipogon, four from Oryza longistaminata and one each from Oryza officinalis and Oryza latifolia were found tolerant to drought stress. These selected accessions were further phenotype for root morphology. The average root length among the selected accessions ranges between 36 and 80 cm and the number of primary roots vary from 30 to 87 cm. The O. rufipogon accession IRGC 106433, O. longistaminata accession IRGC 92656A, O. officinalis accession IRGC 101152 and O. latifolia accession IRGC 80769 showed approximately 2–2.5 times longer root length and number than the indica rice elite cultivar PR121. The results indicated potentiality of selected wild species germplasm for conferring drought tolerance to the elite cultivars.

This study evaluated the effects of organic agriculture manuring systems on carrot (Daucus carota) root morphology and sugar and polyacetylene content. Carrots were harvested three times per season 2006–2007 in a long-term field experiment at Skilleby research farm, Sweden. The effects of pelleted chicken manure, fresh farmyard manure and composted farmyard manure (COM) were compared against control plots left unmanured since the field experiment started in 1991. The carrots were analyzed for root size, root shape, amount of soluble sugars and amount of falcarinol-type polyacetylenes. Differences between manuring systems were found to be smaller than the variation between harvest years and harvest occasions, probably due to the grass-clover ley included in the crop rotation system. On an average for the six harvests, manuring with COM increased root length by 6% compared with fertilizing with pelleted chicken manure. Carrots fertilized with pelleted chicken manure also had 6–7% lower total soluble sugar content than carrots manured with 50 t ha−1 of composted or fresh manure. The falcarinol to total falcarinol-type polyacetylenes ratio was 15.4% in carrots manured with 50 t ha−1 of composted or fresh manure and 14.7% in carrots fertilized with pelleted chicken manure. Seasonal fluctuations in falcarinol-type polyacetylenes were more pronounced in carrots manured with fresh or composted manure than in carrots fertilized with pelleted chicken manure. The results suggest that manuring organic carrots with compost may be the most beneficial strategy, at least in systems where fertilizer is applied only once per crop rotation, whether directly to the carrot crop or in the preceding crop.

In this study, a forward-genetics analysis was performed on a portion of TILLMore, a chemically mutagenized population of barley cv. ‘Morex’ (http://www.distagenomics.unibo.it/TILLMore/), to identify root morphology alterations by comparison with ‘Morex’ wild-type. For this purpose, a simple paper-roll approach was performed to identify phenotypic variants at the seedling stage. The analysis of c. 1000 M4 families allowed us to identify c. 70 lines with altered root morphology. A more accurate phenotypic characterization of a portion of the mutant lines has been performed using stereomicroscopy and a scanning electron microscopy approach.

Root turnover is important to the global carbon budget as well as to nutrient cycling in ecosystems and to the success of individual plants. Our ability to predict the effects of environmental change on root turnover is limited by the difficulty of measuring root dynamics, but emerging evidence suggests that roots, like leaves, possess suites of interrelated traits that are linked to their life span. In graminoids, high tissue density has been linked to increased root longevity. Other studies have found root longevity to be positively correlated with mycorrhizal colonization and negatively correlated with nitrogen concentration, root maintenance respiration and specific root length. Among fruit trees, apple roots (which are of relatively small diameter, low tissue density and have little lignification of the exodermis) have much shorter life spans than the roots of citrus, which have opposite traits. Likewise, within the branched network of the fine root system, the finest roots with no daughter roots tend to have higher N concentrations, faster maintenance respiration, higher specific root length and shorter life spans than secondary and tertiary roots that bear daughter roots. Mycorrhizal colonization can enhance root longevity by diverse mechanisms, including enhanced tolerance of drying soil and enhanced defence against root pathogens. Many variables involved in building roots might affect root longevity, including root diameter, tissue density, N concentration, mycorrhizal fungal colonization and accumulation of secondary phenolic compounds. These root traits are highly plastic and are strongly affected by resource supply (CO2, N, P and water). Therefore the response of root longevity to altered resource availability associated with climate change can be estimated by considering how changes in resource availability affect root construction and physiology. A cost–benefit approach to predicting root longevity assumes that a plant maintains a root only until the efficiency of resource acquisition is maximized. Using an efficiency model, we show that reduced tissue Nconcentration and reduced root maintenance respiration, both of which are predicted to result from elevated CO2, should lead to slightly longer root life spans. Complex interactions with soil biota and shifts in plant defences against root herbivory and parasitism, which are not included in the present efficiency model, might alter the effects of future climate change on root longevity in unpredicted ways.