•Critical integration of the mechanisms of action of humic substances on plant growth.•What are proven facts and what are hypothetical?.•The complexing pathway and the biochemical pathway in HS ...effects on plant nutrition.•Relevance of the nutritional and stimulant effects of humic substances in plants.•Crosstalk between HS-mediated effects on root functionality and shoot growth.
The ability of rhizospheric humic substances to improve plant growth has been well established by many studies carried out using diverse plant species cultivated under many different conditions. These beneficial effects of humic substances on plant development are expressed in both root and shoot. However, the mechanisms responsible for this action of humic substances are only partially known and poorly integrated. In fact, although the studies focused on plant root development are numerous, those dealing with plant shoot development are scarce. Likewise, studies integrating humic effects on root and shoot are also few.
In this context, the main goal of this work is to summarize some of the results regarding the effects of humic substances on plant development within a hypothetical holistic framework that will allow us to interconnect these findings and disclose some features of the functional crosstalk between the effects on soil, root and shoot. Furthermore, the significance of all these mechanisms in plants growing in the field is also discussed.
Plastic-film mulching has played an important role to promote agricultural production in arid areas; however, due to its inefficient recycling capacity, large amounts of residues have been ...accumulated in soils, causing negative impacts on crop growth and on the environment. To investigate these effects on water use efficiency, a two-years field experiment was carried out, applying different levels of plastic-film residues, from 0 to 600 kg ha−1. Results show that these residues have a negative impact on root and shoot growth at several growth stages of corn crop, particularly if above 300 kg ha−1. Root length and weight density decrease with the amount of residues throughout the majority of crop season. Plastic-film residues of about 600 kg ha−1 are responsible for the decrease of the biomass root to shoot ratio during the tasseling stage. Moreover, during physiological maturity, root and shoot revealed the highest sensitivity, and the least negative effects on the root system. Results also show that crop water consumption has a slight decrease with the plastic-film residues, though there was also a significant decrease of the yield and the water use efficiency reduction. This information allows to state that it is determinant to learn how to deal with the problem, adjusting the irrigation and crop management to avoid yield impacts. It would also be important to find an efficient procedure to mechanically collect the residues in the soil, and to apply new biodegradable film mulching.
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•Residual plastic film (RPF) affects root systems with different diameters.•In the 0–30 cm soil layer, root length density (RLD) was most affected by RPF.•Root to shoot ratio (RSR) decreases with an increase of RPF.•The corn root and shoot sensitivity for RPF increased with an increase of RPF.•The yield and water use efficiency (WUE) decreased obviously under the RPF.
Productivity of rice, world's most important cereal is threatened by high temperature stress, intensified by climate change. Development of heat stress-tolerant varieties is one of the best ...strategies to maintain its productivity. However, heat stress tolerance is a multigenic trait and the candidate genes are poorly known. Therefore, we aimed to identify quantitative trait loci (QTL) for vegetative stage tolerance to heat stress in rice and the corresponding candidate genes. We used genotyping-by-sequencing to generate single nucleotide polymorphic (SNP) markers and genotype 150 F
recombinant inbred lines (RILs) obtained by crossing heat tolerant "N22" and heat susceptible "IR64" varieties. A linkage map was constructed using 4,074 high quality SNP markers that corresponded to 1,638 recombinationally unique events in this mapping population. Six QTL for root length and two for shoot length under control conditions with 2.1-12% effect were identified. One QTL
was identified for "root length under heat stress," with 20.4% effect. Four QTL were identified for "root length under heat stress as percent of control" that explained the total phenotypic variation from 5.2 to 8.6%. Three QTL with 5.3-10.2% effect were identified for "shoot length under heat stress," and seven QTL with 6.6-19% effect were identified for "shoot length under heat stress expressed as percentage of control." Among the QTL identified six were overlapping between those identified using shoot traits and root traits: two were overlapping between QTL identified for "shoot length under heat stress" and "root length expressed as percentage of control" and two QTL for "shoot length as percentage of control" were overlapping a QTL each for "root length as percentage of control" and "shoot length under heat stress." Genes coding 1,037 potential transcripts were identified based on their location in 10 QTL regions for vegetative stage heat stress tolerance. Among these, 213 transcript annotations were reported to be connected to stress tolerance in previous research in the literature. These putative candidate genes included transcription factors, chaperone proteins (e.g., alpha-crystallin family heat shock protein 20 and DNAJ homolog heat shock protein), proteases, protein kinases, phospholipases, and proteins related to disease resistance and defense and several novel proteins currently annotated as expressed and hypothetical proteins.
Abstract
Climate change alters both water and
CO
2
availability for plants, but it is largely unknown how they interact with light to affect tree seedling establishment and early growth. Light ...availability is often regulated by forest management, thus understanding how these resources co‐limit the regeneration success of tree species and populations with contrasting drought tolerances is essential for adaptive forest management and particularly for assisted migration.
We studied biomass partitioning of 3‐year‐old Scots pine (
Pinus sylvestris
) and European black pine (
Pinus nigra
) seedlings in response to combined effects of light (22% and 40% shade), soil water availability (moist and dry conditions) and
CO
2
(ambient and elevated), and examined the responses of seedlings from Central Alpine and Mediterranean origin. Seedlings of nine populations with varying drought tolerances were grown in a common garden in the European Central Alps. Shoot height, vertical root length, shoot and root biomass of the plants were assessed at the end of the third growing season.
Under 40% shade and dry conditions,
P. sylvestris
seedlings severely reduced shoot biomass, resulting in an increased specific shoot height (
SSH
) compared to seedlings under 22% shade and moist conditions. In contrast,
P. nigra
seedlings retained a constant shoot biomass under all treatment combinations. Seedlings from drier origin were generally larger, heavier and had longer vertical roots than those from wetter locations. In order to keep up shoot height, seedlings from wetter origins disproportionately increased
SSH
under shaded conditions compared to populations from drier origin.
Synthesis and applications
. Under high light availability, Scots pine (
Pinus sylvestris
) and European black pine (
Pinus nigra
) seedlings were well adapted to dry conditions. Moderate shading, however, substantially reduced Scots pine but not black pine growth, and potentially amplified the vulnerability of Scots pine seedlings to drought. Optimising light conditions in forests, for example by thinning, may thus enhance early Scots pine regeneration in a drier future climate.
Under high light availability, Scots pine (
Pinus sylvestris
) and European black pine (
Pinus nigra
) seedlings were well adapted to dry conditions. Moderate shading, however, substantially reduced Scots pine but not black pine growth, and potentially amplified the vulnerability of Scots pine seedlings to drought. Optimising light conditions in forests, for example by thinning, may thus enhance early Scots pine regeneration in a drier future climate.
Abstract
Brassinosteroid-insensitive-1 (BRI1) plays important roles in various signalling pathways controlling plant growth and development. However, the regulatory mechanism of BRI1 in ...brassinosteroid (BR)-mediated signalling for shoot growth and wood formation in woody plants is largely unknown. In this study, PtBRI1.2, a brassinosteroid-insensitive-1 gene, was overexpressed in poplar. Shoot growth and wood formation of transgenic plants were examined and the regulatory genes involved were verified. PtBRI1.2 was localized to the plasma membrane, with a predominant expression in leaves. Ectopic expression of PtBRI1.2 in Arabidopsis bri1-201 and bri1-5 mutants rescued their retarded-growth phenotype. Overexpression of PtBRI1.2 in poplar promoted shoot growth and wood formation in transgenic plants. Further studies revealed that overexpression of PtBRI1.2 promoted the accumulation of PtBZR1 (BRASSINAZOLE RESISTANT1) in the nucleus, which subsequently activated PtWNDs (WOOD-ASSOCIATED NAC DOMAIN transcription factors) to up-regulate expression of secondary cell wall biosynthesis genes involved in wood formation. Our results suggest that PtBRI1.2 plays a crucial role in regulating shoot growth and wood formation by activating BR signalling.
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•Riparian trees regenerate vegetatively after physical disturbance via resprouting.•Coppice timing and height affects stored starch usage but not shoot volume produced.•Stored ...reserves satisfy demands for maintaining biomass and recovery.•Coppicing can promote tree regeneration where conditions don’t support recruitment.
Human modification of waterways has reduced flooding in many river systems, leading to the decline of riparian forests, which rely on flooding for their regeneration. Coppicing may help to promote the persistence of riparian trees by triggering resprouting and vegetative regeneration. The vigour of resprouting plants can vary with timing and height of coppicing and may depend on stored non-structural carbohydrate reserves like starch, the availability of which can vary seasonally. However, starch storage dynamics and the resprouting potential of broad-leafed evergreen riparian trees is not well understood.
We coppiced two riparian tree species, Eucalyptus camphora and Melaleuca squarrosa, at two different times (autumn, spring) and at two different heights (0 cm and 90 cm). Over 52 weeks, we regularly quantified shoot growth and changes in the starch storage pool size, compared to uncoppiced control trees, in different tree organs (root and stem) and estimated the final shoot volume.
The final shoot volume did not differ significantly between coppice treatments. Trees coppiced in autumn had a greater reliance on stored starch while they remained leafless (without shoots) over winter. Trees cut at 90 cm had more starch reserves due to remaining stems but also had higher biomass maintenance costs. Starch storage varied seasonally only in E. camphora, with starch concentrations in control trees increasing over winter and decreasing over summer.
Although coppice timing and height affected use of stored starch, resprouting in our study species was not limited by starch availability - both species regenerated vegetatively to recover from physical disturbance. Thus, coppicing may be an efficient means to promote rejuvenation and persistence of tree species where site and tree condition are degraded and no longer support recruitment.
Although boron (B) is an element that has long been assumed to be an essential plant micronutrient, this assumption has been recently questioned. Cumulative evidence has demonstrated that the players ...associated with B uptake and translocation by plant roots include a sophisticated set of proteins used to cope with B levels in the soil solution. Here, we summarize compelling evidence supporting the essential role of B in mediating plant developmental programs. Overall, most plant species studied to date have exhibited specific B transporters with tight genetic coordination in response to B levels in the soil. These transporters can uptake B from the soil, which is a highly uncommon occurrence for toxic elements. Moreover, the current tools available to determine B levels cannot precisely determine B translocation dynamics. We posit that B plays a key role in plant metabolic activities. Its importance in the regulation of development of the root and shoot meristem is associated with plant developmental phase transitions, which are crucial processes in the completion of their life cycle. We provide further evidence that plants need to acquire sufficient amounts of B while protecting themselves from its toxic effects. Thus, the development of
and
approaches is required to accurately determine B levels, and subsequently, to define unambiguously the function of B in terrestrial plants.
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