Theoretical and Experimental Plant Physiology最新文献

Nitrate and ammonium are the main sources through which plants obtain nitrogen from the soil. Nevertheless, several plant species exhibit symptoms of toxicity when grown with ammonium, including reduced root growth. As nitrite derived from nitrate is the primary pathway for nitric oxide (NO) synthesis, environments containing ammonium as the sole nitrogen source have lower concentrations of this signaling molecule. Application of NO can enhance plant tolerance to stresses. In our study, the effect of NO application on seedlings of two tree species from the Atlantic Forest with different nitrogen utilization strategies and contrasting tolerances to ammonium was evaluated. The tolerant species Cariniana estrellensis did not show a significant difference in root growth under nitrate or ammonium. However, the non-tolerant species Cecropia pachystachya showed low growth when supplied with ammonium. Malondialdehyde did not accumulate in both species, suggesting that ammonium toxicity is not related to oxidative stress. As expected, C. pachystachya roots exhibited higher concentration of NO when grown with nitrate but C. estrellensis displayed higher endogenous concentration of NO when supplied with ammonium, suggesting a predominance of NO synthesis through oxidative pathways. NO application increased root growth in C. pachystachya seedlings grown in ammonium but had no effect on C. estrellensis. Together, these results suggest that greater tolerance to ammonium may be related to higher concentrations of NO and its modulating role in anti-stress responses. Further investigation with a broader range of species is necessary to identify the mechanisms underlying ammonium tolerance and NO production.

Plant stress state is defined here as an endogenous physiological condition associated with homeostasis disruption involving irreversible or reversible modifications. Plant biologists are facing two important problems: establishing a suitable and dynamic stress concept and devising tools to make a suitable physiological diagnosis to characterize plant stress states. We are proposing here a new concept on stress essentially focused on plant organization as self-organized and emergent systems concentrated in homeostasis disruption as impacted by endogenous and environmental feedbacks. In addition, we are proposing a simplified physiological diagnosis system to evaluate two contrasting stress states in comparison with a non-stressed condition based on progressive alterations in plant homeostasis. This proposal is focused on specific crops, presenting rice as an example. The diagnosis system assumes that homeostasis in plants is dynamic, flexible, spatio-temporal, and organized in multi-modules. The reference state involves a ground homeostasis representing a non-stress state, prior to environmental perturbations and alarm phase. The second stage of homeostatic alterations is characterized by reversible changes in plant organization induced by external factors, characterizing a slightly changed homeostasis or moderate stress state. The third stress state is characterized by strong and irreversible alterations in homeostasis, characterizing collapse in most plant modules leading to a chronic stress. The alterations in the homeostasis induced by mild stressful conditions (eustress) could also trigger different plant memory processes. We believe this systemic stress concept and diagnosis system will shed light on the improvement of stress plant physiology and their respective applications in agriculture.

Abstract

In regions of low soil phosphorus (P) availability, such as many tropical and subtropical regions, the cultivation of eucalypts is common due to their adaptation to P-constrained soils. As in other trees, the molecular mechanisms underlying the phosphate starvation response (PSR) in eucalypts remain poorly understood. This study aimed to elucidate the molecular responses associated with PSR and assess the efficiency of P acquisition in five eucalypt species: Eucalyptus acmenoides, E. grandis, E. globulus, E. tereticornis, and Corymbia maculata. A greenhouse experiment was carried out in soil/substrate with low resin-extractable P (4.5 mg kg⁻¹, Low P) and sufficient P (10.8 mg kg⁻¹, Sufficient P) availability. After nine months growing in such conditions, various parameters were assessed, such as biomass production, P concentrations, P uptake efficiency (PUpE), and the expression of PSR-related genes. Overall, eucalypt plants exhibited a relatively weak response to low P availability, with slight variations in biomass production, P concentration, and PSR gene expression. C. maculata plants exhibited the highest PUpE under low P, while E. globulus exhibited the lowest. Among PSR-related genes, LPR1/2 in the roots of E. grandis, PDR2 in the roots of C. maculata, and phosphate transporters PHT1;6 and PHT1;8 in the roots of E. globulus, along with PHT1;12 in the roots of E. tereticornis, were induced under low P availability. Elevated PHT1 transcripts in the roots under sufficient P conditions, despite adequate leaf P concentrations, suggest potential interactions with other nutrient availability such as nitrogen, magnesium, and calcium, as well as symbiotic associations. Additionally, the upregulation SQD1 gene involved in membrane lipid remodeling in leaves of E. tereticornis, E. acmenoides, and C. maculata under low P suggests an improved P utilization efficiency. This study reveals the intricate and multifaceted nature of eucalypt responses to soil P availability. Despite the low P concentrations, eucalypt plants maintained foliar concentrations similar to those in the P-sufficient treatment suggesting a complex interplay of factors influencing PSR including nutrient balance.

Plants are able to reprogram their metabolism to cope with drought stress based on previous signals of water deficit events. Recently, we reported that oil palm seedlings exposed to three water deficit cycles attenuate oxidative damage on the photosynthetic machinery when compared to those facing drought conditions for the first time. However, the mechanism underlying the photosynthetic apparatus maintenance at either single or repeated events of drought stress is not well understood. Herein, oil palm seedlings were investigated for their photosynthesis acclimation upon single (1WD) and repeated (3WD) events of drought by assessing leaf gas exchange, chlorophyll fluorescence, and biochemical variables when predawn leaf water potential of stressed plants reached about –1.7 MPa (Day 7) and 2.5 MPa (Day 28). Plants of 1WD treatment exhibited higher chlorophyll degradation, higher membrane lipid peroxidation, and lower photosystem II activity than both control and 3WD plants. In contrast, 3WD plants exhibited low hydrogen peroxide coupled with upregulation of the enzymatic antioxidant system. The outcomes suggest that the acclimation of oil palm plants to repetitive water deficit events is related to the adjustments in antioxidant enzyme activities to attenuate oxidative damage to the photosynthetic machinery.

Abstract

The soil seed banks are composed of seeds from distinct origins and species, including dormant and non-dormant ones. Seed banks were formed by seeds dispersed from parent plants receiving from them important information regarding the environment. The dormant seeds, especially with physiological dormancy, can persist in these banks longer than non-dormant seeds. As long as they persist, it is possible to access memories from the timing of formation and persistence in the soil seed banks. However, besides the physiological dormancy is a natural trait that assures seed germination and seedling recruitment when the environmental conditions are favorable, some practical implications can be discussed. Here I bring a perspective of how the memories of the seeds in the soil seed banks, mainly regarding dormant seeds, can help predict intraspecific variability (i.e., epigenetics) losses and what can be done to slow down this negative effect among species. Each seed is a source of genetic and memory of the time that the seed was formed in the mother plant and the timing of the permanency in the soil seed bank, therefore, each seed of each species counts for restauration efforts. This knowledge is crucial for avoiding directional selection when non-dormant and quick-germinating seeds are selected for recovering areas. Moreover, it is imperative to keep untouched areas where the soil seed banks indeed represent the structure of the reference population.

Abiotic stresses are among the primary environmental variables that have consistently posed challenges to agricultural production worldwide. In the last decades, our understanding of how plants sense environmental cues has greatly expanded. This encompasses the mechanisms that convert environmental stress signals into cellular signaling pathways and gene transcription networks. Moreover, emerging evidence indicates that plants have the capacity to retain memories of past stressful experiences and use such capacity to enhance their responses under recurrent stresses. Priming, through prior exposure to a triggering factor, improves plant tolerance to subsequent biotic or abiotic stresses and has been proposed as the basis for plant stress memory. Priming-induced stress memory can persist in the current generation or even in the progeny. The significance of stress memory in enhancing abiotic stress tolerance is well-established in several important crops, and the capacity of plants to retain stress-related memories has been linked to diverse plant mechanisms. In this review, we revisit the recent literature reporting the mechanistic underpinnings of abiotic stress memory in important crops. We outline the underlying processes related to acquisition of stress memory, occurring at molecular, physiological, biochemical, and morphological levels. Here, we addressed the methods for studying plant memory over the last ten years, giving special attention to growth conditions, phenological stages and the techniques for inducing crop memory. Enhancing our comprehension of stress memory-related mechanisms would open up a range of possibilities for developing stress-resistant genotypes through molecular breeding or biotechnological methods or even stress-resistant crop fields due to improved management practices.

The photosynthetic capacity is contingent upon the balance between nitrogen (N) and phosphorus (P) concentration, as well as environmental factors. Ensuring a balanced and timely supply of nitrogen and phosphorus facilitated healthy leaf growth and sustained efficient photosynthetic activity during trees active growth phases. However, the effects of the interactions between these factors on photosynthesis, particularly in the unique context of karst ecosystems, remain unclear. To address this, we conducted an assessment of photosynthetic parameters, including the 25 ℃ maximum carboxylation rate (V_cmax,25) and the 25 ℃ maximum electron transport rate (J_max,25), and chemical traits of leaves (leaf N, leaf P, and N:P ratio) in nine locally dominant species across both subtropical non-karst and karst areas in southwestern China. Our findings revealed that concentrations of leaf phosphorus and soil phosphorus were significantly higher in karst areas compared to non-karst areas. Additionally, the V_cmax,25 of both karst and non-karst species were synergistically affected by leaf N and P concentrations, rather than being constrained by least available nutrient. Specifically, V_cmax,25 of karst species was strongly related to leaf P, and increasing leaf N substantially increased the sensitivity of V_cmax,25 to leaf P, highlighting the importance of maintaining a balance between N and P concentrations. These insights substantially enhance the understanding of photosynthetic dynamics and resource management in diverse ecosystems, providing a solid foundation for further research and conservation strategies.

Abstract

Due to the already strained and severely challenged agricultural ecosystems of the modern world, predicted changes in life cycle of plants, including leaf senescence are receiving significant attention from stakeholders. The onset, progression and terminal phases of leaf senescence are greatly influenced by plant hormones. The senescence of leaves is accelerated by ethylene, jasmonic acid (JA), salicylic acid (SA), abscisic acid (ABA), brassinosteroids and strigolactones (SLs), whereas it is postponed by cytokinins (CKs), gibberellic acid (GA) and auxins. The crosstalk and signal transduction pathways between these growth regulators have been found to regulate leaf senescence by orchestrating various developmental and environmental factors. Premature leaf senescence lessens the plant’s nutritional capacity and shortens the vegetative production schedule, prompting an early transition from the vegetative to the reproductive stage and diminishing crop potential. As a result, a complete understanding of leaf senescence and finding novel ways to delay it is crucial for agricultural productivity. The ability to manipulate leaf senescence for agricultural enhancement has been made possible by significant advances in physiological and molecular awareness of leaf senescence. Although studies pertaining to leaf senescence have been given steadily more attention, there are still numerous challenges that need to be resolved. In this perspective, this review focuses on current advances in understanding the leaf senescence by molecular and genetic analyses with an emphasis on hormonal regulation of leaf senescence. We also hypothesize future research to better comprehend leaf senescence by employing various current technologies.

A promising approach to solve the problem of tolerance of plants in hostile environments is to focus of stress tolerance mechanisms of extremophilic plants, in particular mosses. Along with the universal stress mechanisms, bryophytes exhibit a unique spectrum of secondary metabolites such as carotenoids, a lipophilic metabolite derived from the isoprenoid pathway. The main representatives of carotenoids in mosses are α- and β-carotene, lutein, neo-, viola- and zeaxanthins. Hylocomium splendens is one of the most common and widespread mosses of Northern Hemisphere. The genome of this moss has not been sequenced, and the carotenoid biosynthesis pathway (CBP) genes of this species have not been reported to date. This is the first report to of an attempt to identify and characterize the CBP genes in H. splendens. As a result of cloning, sequencing, and in silico analysis, we identified and characterized ten CBP genes in H. splendens with a full ORF, and prediction of subcellular localization suggests chloroplast localization of CBP proteins. Using multiple alignments and phylogenetic and homology analyses, we demonstrated that the CBP genes of H. splendens share high similarity with the sequences in other bryophytes. Differential expression of CBP transcripts during abiotic stresses was more evident for genes in the middle and downstream steps of CBP. This work provides information on the molecular genetics of CBP in extremophilic bryophytes. Analysis of CBP genes can help to unravel the genetic evolution of carotenoid biosynthesis in plants.

Abstract

We commence our discussion by asserting that Plant Physiology is fundamentally focused on comprehending the evolutionary and adaptive processes of plants over time. Despite its intuitive association with the temporal dimension, the field has traditionally been underpinned by methods that largely overlook the temporal element. Even in this era of advanced scientific techniques, many studies in plant science continue to employ methods that are essentially “timeless”. Therefore, our comprehension of plant processes “across time” tends to be fragmented. Instead of observing a continuous, real-time progression, we aggregate averaged measurements from various samples collected at discrete time points. This approach provides insights into the temporal aspects of biological processes, analogous to snapshots extracted from a movie, but it falls short of capturing the full dynamism of these processes. The understanding of these temporal aspects holds paramount significance in the realm of plant biology, as plants, by their inherent nature, represent intricate systems. Consequently, the concept of time assumes pivotal importance, and the present article elucidates a spectrum of philosophical perspectives and scientific interpretations of time. Comprehending the diverse facets of time is indispensable within the domain of plant physiology. It serves as a gateway to a more comprehensive and dynamic exploration of plant processes. This amalgamation of philosophy and science enables us to perceive plant biology as a continuum of processes unfolding over time, accentuating the interconnectedness of internal and external events. In this context, we assert that Processual Philosophy provides a suitable and reliable foundation for the development of Plant Physiology as a science dedicated to the temporal dimensions of plant life.