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The emergence of alternative stable states in forest systems has significant implications for the functioning and structure of the terrestrial biosphere, yet empirical evidence remains scarce. Here, we combine global forest biodiversity observations and simulations to test for alternative stable states in the presence of evergreen and deciduous forest types. We reveal a bimodal distribution of forest leaf types across temperate regions of the Northern Hemisphere that cannot be explained by the environment alone, suggesting signatures of alternative forest states. Moreover, we empirically demonstrate the existence of positive feedbacks in tree growth, recruitment and mortality, with trees having 4–43% higher growth rates, 14–17% higher survival rates and 4–7 times higher recruitment rates when they are surrounded by trees of their own leaf type. Simulations show that the observed positive feedbacks are necessary and sufficient to generate alternative forest states, which also lead to dependency on history (hysteresis) during ecosystem transition from evergreen to deciduous forests and vice versa. We identify hotspots of bistable forest types in evergreen-deciduous ecotones, which are likely driven by soil-related positive feedbacks. These findings are integral to predicting the distribution of forest biomes, and aid to our understanding of biodiversity, carbon turnover, and terrestrial climate feedbacks. Alternative stable states in forests have implications for the biosphere. Here, the authors combine forest biodiversity observations and simulations revealing that leaf types across temperate regions of the NH follow a bimodal distribution suggesting signatures of alternative forest states.

Abstract Green lettuce (Lactuca sativa L.) is a popular leafy vegetable grown and consumed worldwide for its crisp texture and nutritional value. This study investigates the impact of different inorganic fertilizers on the growth and productivity of green lettuce, with the aim of determining the most effective fertilizers for producing vibrant green lettuce. The research was carried out at the Jaya Wijaya Research Centre, Faculty of Agriculture, Slamet Riyadi University, employing a randomized design with a single factor: the type of inorganic fertilizer. The experimental treatments included Nutrimax, NPK 25.7.7, and a control group, each replicated four times. Lettuce plants treated with Nutrimax exhibited superior performance across various metrics, including plant height (32.63 cm), leaf color intensity (3.25), leaf count (13.5 leaves), fresh weight (94.75 grams), and dry weight (5.33 grams). Statistical analysis using Analysis of Variance, followed by the Least Significant Difference test at a significance level of 5%, revealed a significant influence of fertilizer treatment on the growth and yield of green lettuce plants. The type of fertilizer applied significantly affected the growth and yield of green lettuce cultivated using a floating hydroponic system. The number of leaves on the plant directly impacted the fresh weight of the leafy vegetables. These findings can serve as a valuable guide for optimizing green lettuce cultivation practices to achieve maximum yields. Resumo A alface verde (Lactuca sativa L.) é uma hortaliça folhosa popular cultivada e consumida em todo o mundo por sua textura crocante e valor nutricional. Este estudo investiga o impacto de diferentes fertilizantes inorgânicos no crescimento e produtividade da alface verde, com o objetivo de determinar os fertilizantes mais eficazes para a produção de alface verde crespa. A pesquisa foi realizada no Centro de Pesquisa Jaya Wijaya, Faculdade de Agricultura, Universidade Slamet Riyadi, empregando um desenho randomizado com um único fator: o tipo de fertilizante inorgânico. Os tratamentos experimentais incluíram Nutrimax, NPK 25.7.7 e um grupo controle, cada um replicado quatro vezes. As plantas de alface tratadas com Nutrimax exibiram desempenho superior em várias métricas, incluindo altura da planta (32,63 cm), intensidade da cor das folhas (3,25), contagem de folhas (13,5 folhas), peso fresco (94,75 gramas) e peso seco (5,33 gramas). A análise estatística por meio da Análise de Variância, seguida do teste de Diferença Mínima Significativa ao nível de significância de 5%, revelou influência significativa do tratamento com fertilizantes no crescimento e produtividade de plantas de alface verde. O tipo de fertilizante aplicado afetou significativamente o crescimento e a produtividade da alface verde cultivada em sistema hidropônico flutuante. O número de folhas da planta impactou diretamente na massa fresca das hortaliças folhosas. Essas descobertas podem servir como um guia valioso para otimizar as práticas de cultivo de alface verde para alcançar rendimentos máximos.

The phytohormone jasmonoyl-isoleucine (JA-Ile) regulates defense, growth and developmental responses in vascular plants. Bryophytes have conserved sequences for all JA-Ile signaling pathway components but lack JA-Ile. We show that, in spite of 450 million years of independent evolution, the JA-Ile receptor COI1 is functionally conserved between the bryophyte Marchantia polymorpha and the eudicot Arabidopsis thaliana but COI1 responds to different ligands in each species. We identified the ligand of Marchantia MpCOI1 as two isomeric forms of the JA-Ile precursor dinor-OPDA (dinor-cis-OPDA and dinor-iso-OPDA). We demonstrate that AtCOI1 functionally complements Mpcoi1 mutation and confers JA-Ile responsiveness and that a single-residue substitution in MpCOI1 is responsible for the evolutionary switch in ligand specificity. Our results identify the ancestral bioactive jasmonate and clarify its biosynthetic pathway, demonstrate the functional conservation of its signaling pathway, and show that JA-Ile and COI1 emergence in vascular plants required co-evolution of hormone biosynthetic complexity and receptor specificity.

Efficient use of nitrogen inputs for concurrent improvements in grain yield and nitrogen use efficiency (NUE) has been recognized as a viable strategy for sustainable agriculture development. Yet, there is little research on the possible physiological basis of maize hybrid heterosis for NUE and measurable traits that are corresponding to the NUE heterosis. A field study was conducted for two years to evaluate the heterosis for NUE and determine the relationship between NUE and its physiological components. Two commercial hybrids, ‘Xianyu335’ and ‘Zhengdan958’, and their parental inbred lines, were grown at 0 (0 N) and 150 kg N ha −1 (150 N), in a randomized complete block design with four replications each year. Compared to their parental lines, both hybrids displayed a significant heterosis, up to 466%, for NUE. N internal efficiency (NIE) accounted for 52% of the variation in heterosis for NUE, while there was generally negligible heterosis for nitrogen recovery efficiency (NRE). Heterosis for NIE and thereby for NUE in maize was ascribed to (i) an earlier establishment of pre-anthesis source for N accumulation, which phenotypically exhibited as a faster leaf appearance rate with higher maximum LAI and photosynthetic nitrogen use efficiency; (ii) a larger amount of N being remobilized from the vegetative tissues, especially from leaves, during the grain filling. Phenotypically, there was notably a rapid reduction in post-anthesis specific weights of leaf and stalk, but with maintained functionally stay-green ear leaves; and (iii) a higher productive efficiency per unit grain N, which was characterized by a reduced grain N concentration and enhanced sink strength.

We have studied autumn leaf senescence in a free-growing aspen (Populus tremula) by following changes in pigment, metabolite and nutrient content, photosynthesis, and cell and organelle integrity. The senescence process started on September 11, 2003, apparently initiated solely by the photoperiod, and progressed steadily without any obvious influence of other environmental signals. For example, after this date, senescing leaves accumulated anthocyanins in response to conditions inducing photooxidative stress, but at the beginning of September the leaves did not. Degradation of leaf constituents took place over an 18-d period, and, although the cells in each leaf did not all senesce in parallel, senescence in the tree as a whole was synchronous. Lutein and [beta]-carotene were degraded in parallel with chlorophyll, whereas neoxanthin and the xanthophyll cycle pigments were retained longer. Chloroplasts in each cell were rapidly converted to gerontoplasts and many, although not all, cells died. From September 19, when chlorophyll levels had dropped by 50%, mitochondrial respiration provided the energy for nutrient remobilization. Remobilization seemed to stop on September 29, probably due to the cessation of phloem transport, but, up to abscission of the last leaves (over 1 week later), some cells were metabolically active and had chlorophyll-containing gerontoplasts. About 80% of the nitrogen and phosphorus was remobilized, and on September 29 a sudden change occurred in the [delta]¹⁵N of the cellular content, indicating that volatile compounds may have been released.

Depending on the strength of environmental filtering and competitive exclusion, successful colonizers of plant communities show varying degrees of similarity to resident species with respect to functional traits. For the present study, colonizer’s performance was assessed in relation to the degree of fit with the resident community, and in addition, in relation to the community’s trait profile and the environmental factors at the study locations. The two-year field experiment investigated the relative growth rates of 130 species that had been transplanted into German grassland communities varying in intensities of land-use. The transplanted species were selected in accordance with the following scenarios: species with highly similar or dissimilar traits to residents, species with highest degree of co-occurrence with resident species and species chosen randomly from the local species pool. The performance of transplanted phytometers depended on the scenario according to which the species were selected, on community trait diversity, and in addition, often on the interaction of both and on land use intensity. The total amount of explained variance in performance was low, but increased considerably when species identity was taken into account. In general, individuals in the co-occurrence scenario performed better than those selected based on trait information or those selected randomly. Different predictors were important in different seasons, demonstrating a limited temporal validity of performance models.

Plant hormones known as strigolactones control plant development and interactions between host plants and symbiotic fungi or parasitic weeds 1 – 4 . In Arabidopsis thaliana and rice, the proteins DWARF14 (D14), MORE AXILLARY GROWTH 2 (MAX2), SUPPRESSOR OF MAX2-LIKE 6, 7 and 8 (SMXL6, SMXL7 and SMXL8) and their orthologues form a complex upon strigolactone perception and play a central part in strigolactone signalling 5 – 10 . However, whether and how strigolactones activate downstream transcription remains largely unknown. Here we use a synthetic strigolactone to identify 401 strigolactone-responsive genes in Arabidopsis , and show that these plant hormones regulate shoot branching, leaf shape and anthocyanin accumulation mainly through transcriptional activation of the BRANCHED 1 , TCP DOMAIN PROTEIN 1 and PRODUCTION OF ANTHOCYANIN PIGMENT 1 genes. We find that SMXL6 targets 729 genes in the Arabidopsis genome and represses the transcription of SMXL6 , SMXL7 and SMXL8 by binding directly to their promoters, showing that SMXL6 serves as an autoregulated transcription factor to maintain the homeostasis of strigolactone signalling. These findings reveal an unanticipated mechanism through which a transcriptional repressor of hormone signalling can directly recognize DNA and regulate transcription in higher plants. Many of the molecular targets of strigolactones—plant hormones involved in development and in interactions with symbiotic and parasitic organisms—are uncovered, revealing how strigolactones function and an intriguing role for self-regulation of a downstream transcription factor.

Nitrogen is an essential nutrient for plant growth. World-wide, large quantities of nitrogenous fertilizer are applied to ensure maximum crop productivity. However, nitrogen fertilizer application is expensive and negatively affects the environment, and subsequently human health. A strategy to address this problem is the development of crops that are efficient in acquiring and using nitrogen and that can achieve high seed yields with reduced nitrogen input. This review integrates the current knowledge regarding inorganic and organic nitrogen management at the whole-plant level, spanning from nitrogen uptake to remobilization and utilization in source and sink organs. Plant partitioning and transient storage of inorganic and organic nitrogen forms are evaluated, as is how they affect nitrogen availability, metabolism and mobilization. Essential functions of nitrogen transporters in source and sink organs and their importance in regulating nitrogen movement in support of metabolism, and vegetative and reproductive growth are assessed. Finally, we discuss recent advances in plant engineering, demonstrating that nitrogen transporters are effective targets to improve crop productivity and nitrogen use efficiency. While inorganic and organic nitrogen transporters were examined separately in these studies, they provide valuable clues about how to successfully combine approaches for future crop engineering.

Crop leaves in full sunlight dissipate damaging excess absorbed light energy as heat. When sunlit leaves are shaded by clouds or other leaves, this protective dissipation continues for many minutes and reduces photosynthesis. Calculations have shown that this could cost field crops up to 20% of their potential yield. Here, we describe the bioengineering of an accelerated response to natural shading events in Nicotiana (tobacco), resulting in increased leaf carbon dioxide uptake and plant dry matter productivity by about 15% in fluctuating light. Because the photoprotective mechanism that has been altered is common to all flowering plants and crops, the findings provide proof of concept for a route to obtaining a sustainable increase in productivity for food crops and a much-needed yield jump.

The effect of excess Ni (1 mM Ni) on wheat plants as well as the role of Ca (1 mM Ni+5000 microM Ca) for amelioration of toxicity and recovery of growth and photosynthesis in Ni-stressed wheat was evaluated. Growth, nutrient status (Ca, Mg, Fe, K, Na), and photosynthesis showed a distinct decrease strictly related to the period of treatment. Calcium ameliorated to a certain extent toxic symptoms of Ni, due to antagonistic action between Ni and Ca ions. Since chlorophyll content and variable fluorescence (Fv) decreased significantly, but Fo did not particularly change, the decrease of t1/2 with increasing duration of Ni exposure indicates negative changes on the acceptor side of PSII, which also may result from diminution of Calvin cycle. The maximum quantum yield for energy trapping was also suppressed. Plant transfer to Hoagland solution+5000 microM Ca caused recovery to plant morphology and physiology. Even in control plants, during recovery period an increased Ca concentration in plant tissues with concomitant increased rates of growth and morphology was observed. Ni concentration in plants exposed to 1 mM Ni+5000 microM Ca was lower than in plants exposed to 1 mM Ni. In all treatments a certain increase of plant nutrients was observed during recovery.