Functional Plant Biology

Leaf carbon isotope composition (δ¹³C) has been used to screen for water-use efficiency in C₃ plants, but gaps in the understanding of factors influencing δ¹³C have limited its application in C₄ species. This study exploited maize genetic diversity to explore biochemical and post-photosynthetic factors that may influence δ¹³C. Our findings indicate that the observed variation in leaf carbon isotope composition across diverse maize lines is likely driven by differences in stomatal and mesophyll conductance and not photosynthetic or respiratory metabolism.

Hemlock woolly adelgid (HWA) is an invasive insect that feeds upon the foliage of eastern hemlock trees leading to a decline in health and mortality. During early infestation, HWA-induced decline in the health of eastern hemlock is not initially caused by compromised water transport or needle loss. Our results contribute to efforts to understand the mechanisms leading to the demise of eastern hemlocks.

Stomatal guard cells sense and respond to sugar, but the means by which they do so have not been fully elucidated. Our study showed that RGS1, a putative receptor for D-glucose, mediates D-glucose-induced H₂O₂ and NO production in guard cells and subsequent stomatal closure. The data suggest that photosynthetic product D-glucose, as an integrative signal, coordinates plant CO₂ uptake with water loss.

In the perennial herbaceous wintergreen plant Ajuga reptans (bugle), the photosynthetic apparatus (PSA) is reorganised during winter. The aim of this work was to examine the structural changes in the pigment–protein complexes of PSA. Changes in aggregation of the thylakoid protein complexes were observed including a restructuring of the PSI–PSII megacomplex and the PSII–LHCII supercomplex parallel to changes in the zeaxanthin-dependent protective mechanism.

In the study presented we identified MdDof genes in apple and analysed their response to biotic/abiotic stress. The aim of the work was to give references to understand the function of MdDof genes generally and serve as a reference for studies of Dof zinc finger genes in other plants. Finally, we fit the original images into the software Photoshop 6.0 for bigger pictures.

Abiotic stress reduces the grain yield of cereal crops. Here, we show that the two durum wheat annexin genes, TdAnn6 and TdAnn12, are induced by different abiotic stresses and heterologous expression in yeast improves tolerance to different stresses. These results show that the two annexins are potentially useful candidate genes for engineering abiotic stress tolerance in cultivated plants.

We proved for the first time the effects of H₂S, a novel gasotransmitter, on darkness-induced stomatal closure and the relationship with H₂O₂ in Vicia faba. Here we found that H₂S mediated darkness-induced stomatal closure in Vicia faba and it acted downstream of H₂O₂ in this process. This work enriches the signalling network during darkness-regulated stomatal movement and provides evidence for further research.

Bacterial pathogens secrete effectors to modulate plant immunity, enabling unlimited pathogen growth inside host, and causing disease. Xanthomonas oryzae pv. oryzae executes XopR effector to suppress immune responses in rice for its growth and subsequent blight disease. This finding provides insights into understanding the key weapon used by the pathogen, and will help to identify the novel targets for disease management.

Chilling stress limits the productivity and geographical distribution of many plants throughout the world. Accumulation of the endoplasmic reticulum-located small heat shock protein CaHSP22.5 enhanced photochemical activity and oxidation resistance and alleviated endoplasmic reticulum stress caused by chilling stress in transgenic tobacco plants. CaHSP22.5 could be useful for improving the tolerance of chilling-sensitive plant types.

Whether plants can induce mass flow of nutrient-rich soil water via increased transpiration might influence their competitive strength. We tested the response of C₄ grasses to low nutrient availability at the roots but found no physiological indication of active mass flow induction. This can mean a competitive disadvantage of water-efficient C₄ plants to C₃ plants under high atmospheric CO₂.

We review metabolic adaptations of plant tissues to severe reductions in energy-production (‘energy-crises’) that occur in various situations, including O₂-deprivation during flood-events. We conclude that most major differences between tissues intolerant and tolerant to an energy-crisis are associated with only a few gene-proteins. These concern efficient energy production and energy-efficient-transporters, necessary to retain membrane integrity, essential to life.

This research demonstrated the different growth dynamics in adventitious and lateral roots of barley in response to low-P stress and detected quantitative trait loci (QTLs) for them. Lateral roots play a role in P uptake in barley. The new QTL region Cl⁻2H had great potential for future genetic improvement of barley lateral root growth and may offer valuable clues for fine mapping in barley.

The developing aerenchyma of Typha angustifolia is accompanied by calcium oxalate crystals (CaOx). The degradation of CaOx crystals causes high levels of H₂O₂, which is considered a key signalling molecule that triggers programmed cell death (PCD). It suggested that CaOx degradation is involved in the regulation of the PCD process of aerenchyma in T. angustifolia leaves.

The defence capacity of metal-rich foliage in two rainforest tree species was examined via a field study. Plant–insect interactions associated with tree metallophytes remain poorly understood. Although there was no direct evidence here of metal defence, the study found indirect effects, and evidence of adaptation by a galling insect that exploits foliar metal. This field study revealed complex ecological relationships undetectable by controlled experiments.

Superfluous N is consumed during wheat cultivation, causing environmental problems. Thus N fertiliser applications must be reduced without decreasing yield, which can be achieved by characterising the mechanism of adaptation to low N and breeding N-efficient cultivars. We found that under short-term N-deficient conditions, tolerant cultivars can efficiently reuse stored NO₃^– and photorespiration-released NH₄⁺ to maintain Rubisco content, and promote Rubisco activation to improve photosynthesis, which could help develop long-term N-deficiency tolerance.

To further increase sugarcane yield, it is necessary to understand the dynamics of carbohydrate accumulation and whole-plant partitioning. This paper presents the diurnal variation in gas exchange and nonstructural carbohydrates in the leaves, culm and roots of sugarcane during different stages of development in a field experiment. It gives insights into how the environment and development control sugar and biomass accumulation.

Increasing global demand for high quality, plant-based proteins has driven a strong interest in the sorting and processing of seed storage proteins. This review summarises recent primary research findings regarding vacuolar trafficking and seed protein biology, in the context of established and novel paradigms. We also highlight several key gaps in the scientific understanding of these processes.

Hydrogen gas (H₂) – a unique signal molecule – has broad application prospects in biology. Here, we focus on the fact that H₂ has positive effects on various developmental processes and abiotic stresses through enhancing antioxidant defense system and regulating related genes in plants. With its promising application in plants, hydrogen agriculture will be welcomed in the near future.

Leaf and soil phosphorus have been identified as key factors modulating metabolic rates at leaf and ecosystem levels. We investigated the effect of phosphorus deficiency on leaf trait relationships within a single genus (Eucalyptus). Our results highlight the importance of phosphorus availability in determining relationships between metabolic performance and leaf structural and chemical composition traits in a genus widespread across the Australian continent.

Saline soils limit crop productivity worldwide and highlight the need to study plants of arid-saline lands. The mechanism of survival of Desmostachya bipinnata through proteomic analysis was determined by shortlisting 103 plant proteins involved in energy and salt stress regulation systems. Results may help in developing a salt tolerant crop that could enhance productivity under saline conditions.

Differences in plant hydraulics may explain an important phenotype for drought adaptation: saving water by restricting the transpiration rate, especially under high vapour pressure deficit (VPD). Soil grown roots limited high VPD transpiration, even more so in low Tr genotype. Root water transport was more apoplastic in low Tr genotype and more symplastic in high Tr genotype. These were hypothesised to ‘tune-up’ the aquaporin-mediated symplastic pathway under high VPD.

Grapevine fanleaf virus (GFLV) causes grapevine fanleaf degeneration, one of the oldest known viral diseases of grapevines. Our research showed that GFLV infection caused a drop of the yield due to both a reduction of cluster weight and berry weight. GFLV infection also affected the berry composition due to increase of anthocyanin concentration and modification of proportions between di- and tri-, hydroxylated or methylated derivatives of anthocyanins, due to modified expression of F3ʹ5’H, F3ʹH and F3H1 genes.

Rising [CO₂] is likely to influence plant functioning as well as structure and composition of native ecosystems. Results demonstrated that rising CO₂ will improve biomass allocation to vegetative organs responsible for acquiring crucial resources for growth. The shift in the pattern of biomass allocation would improve the competitive capacity of woody over herbaceous species and potentially change important ecological relationships in the savanna ecosystem of Cerrado.

Drought stress is a major constraint for global rice production. Short-term mild drought priming could improve CO₂ assimilation and sink strength under severe drought. Priming can be considered as an effective strategy in rice to reduce severe yield penalties under drought stress.

Sorghum synthesises the specialised metabolite dhurrin, which, when enzymatically hydrolysed releases hydrogen cyanide, which is toxic to grazing animals. We used dhurrin deficient mutants to test growth–defence trade-offs at different nitrogen fertiliser levels. Plants lacking dhurrin were slower growing as seedlings but had a growth advantage at later developmental stages, suggesting a benefit of dhurrin in early growth but a cost at later stages. To maintain global food security, crop yields must be optimised while resource input is minimised.

Dwindling phosphate reserves and the high costs of P fertilisers drive the need to develop more P-efficient crops through enhancing P uptake. We expected that Aspalathus linearis, a cluster-root-forming species, would be better at P acquisition than other species. Polygala myrtifolia, however, developed a root system with better P uptake traits and had a higher P uptake efficiency. Therefore, other root traits besides cluster roots are important for enhancing P uptake in plants.

Elevated [CO₂] increases rates of photosynthesis and crop yields, but the degree of enhancement varies among cultivars. The present study indicates that the more effective use of CO₂ in IIY compared with WYJ results in a strong response in root growth, nitrogen uptake, and in yield, N synchronises biomass responses between shoot and root. Our findings help clarify key mechanisms by which elevated [CO₂] elicits differential growth and yield responses among cultivars in rice.

Quantitative reverse transcription PCR, a widely used technique for measuring the transcriptional activity of genes, is critically dependent upon the use of reference genes. This manuscript is the first reported systematic search for reference genes in the commercially important forage legume white clover. Three genes, out of seven evaluated, were identified as reliable references, paving the way for future work on any gene in white clover.

Detection of nutrients deficiency in plants has previously been based on either observation of visible changes or destructive estimation methods. Here we identify parameters related to photosynthetic efficiency that enable early detection of Mg deficiency in radish plants before visual symptoms appear. We confirm that some parameters can be used as bioindicators for transient and persistent Mg deficiency.

Salinity stress is one of the major limitations to crop productivity worldwide. The aim of the present study was to understand the functional role of spermidine and spermine with respect to salt stress in wheat seedlings. Our results show that exogenous spermidine and spermine effectively up-regulated transcriptional levels of antioxidant enzyme genes and improved the defence response of plants under salt stress.

Cassava bacterial blight is the most destructive disease of cassava, which results in a significant reduction in cassva production caused by Xanthomonas axonopodis pv. manihotis; however, little is known about the resistance mechanisms of cassava bacterial blight. In our study, MeBIK1, an ortholog of the AtBIK1 gene was cloned from cassava and MeBIK1 was found to positively regulate pathogen resistance. Our results provide the basis for elucidating the mechanism of disease resistance in cassava.

Nitrogen use efficiency (NUE) in most crops is low, resulting in N waste, leading to increased crop production costs and environmental concerns globally. Efficient and reliable phenotyping would help manage N application and speeding up efforts to breed crop varieties with higher NUE. A comprehensive insight is provided into the approaches, tools and methods applicable to phenotyping NUE-related traits in crops.

CAM is a flexible photosynthetic mode conferring robust environmental resilience. This investigation tackles the scarcity of data linking anatomical evolution and CAM function, showing that in a diverse family, co-option and augmentation of existing succulence was integral to multiple CAM origins. The results clarify the evolution of CAM and also help define the baseline level of cell and tissue succulence required in efforts to bioengineer CAM into food and biomass crops.

One of the good news in plants is NO news. NO is an all-around molecule that plays a vital role during the entire life cycle of plants. This study identified a large number of genes that were activated in response to exogenous NO in rice. In conclusion, NO mediates the transcriptional control of genes involved in a wide variety of physiological functions in rice.

The duration of phases leading to wheat anthesis date, and hence yield potential, are regulated by daylength (photoperiod). Genes controlling the response to photoperiod (Ppd-1): (i) provided varying magnitudes of insensitivity; (ii) were not particularly associated to duration – photoperiod sensitivity – of any specific phase; and (iii) showed no additive effect when stacked. Further investigation with different allelic variants should be conducted to tailor time to anthesis and duration of each particular phase to improve wheat yield potential facing climate change.

Guzmania monostachia is an epiphytic, tank-forming bromeliad that displays variable degrees of crassulacean acid metabolism (CAM) along the leaf blade under water deficit conditions. The hypothesis that the most intense CAM found in the apex portion is related to reduced oxidative burden was not confirmed. However, G. monostachia was able to keep reactive oxygen species under tolerable levels under water deficit conditions by increasing the antioxidant capacity in the apex, which is the leaf portion most exposed to light.

Potato is a high nitrogen-responsive crop, hence improving nitrogen use efficiency (NUE) of plant is important to reduce production cost and minimize environmental loss. Potato is a less studied crop especially at plant level with enhanced NUE. This review highlights translation of advanced NUE research from other plants like Arabidopsis, rice, wheat and maize applying integrated genomics, physiology and breeding approaches.