Promoted Leaf Growth Research Articles

Agricultural Biotechnological Potential of Bacillus velezensis C3-3 and Cytobacillus sp. T106 from Resource Islands of a Semi-arid Zone of La Guajira-Colombia

Resource islands are vegetative formations in arid and semi-arid ecosystems that harbor microorganisms facing extreme conditions. However, there is a limitation in the knowledge of the agricultural biotechnological potential of microorganisms present in these islands. This study aimed to determine the capacity of Bacillus velezensis C3-3 and Cytobacillus sp. T106 isolates from resource islands to promote plant growth and control the phytopathogen Rhizoctonia solani. The bacteria were sequenced, and both grew at 50 °C, resisted 5% NaCl, withstood UV exposure, and grew in extreme pH conditions. Sixty-six genes in C3-3 and 71 in T106 were identified associated with plant growth promotion, and C3-3 was shown to promote leaf growth in lettuce plants. This promotional effect was associated with the production of indole-3-acetic acid (IAA), phosphorus solubilization, and the presence of genes related to the assimilation of rhizosphere exudates. Both strains inhibited R. solani through the production of volatile compounds and antagonism. Forty-five and 40 of these genes in C3-3 and T106, respectively, were associated with the production of proteases, lipases, siderophores, antimicrobial compounds, degradation enzymes, and secretion systems. Notably, Cytobacillus sp. has not been previously reported as a biocontrol agent. This work contributes to the evidence of the biotechnological potential of semi-arid region bacteria, offering prospects for improving agricultural production in areas with limiting conditions.

A growth-regulating factor 7 (GRF7)-mediated gene regulatory network promotes leaf growth and expansion in sugarcane

Knowledge of the function of growth-regulating factors (GRFs) in sugarcane (Saccharum officinarum and S. spontaneum) growth and development could assist breeders in selecting desirable plant architectures. However, limited information about GRFs is available in Saccharum due to their polyploidy. In this study, 22 GRFs were identified in the two species and their conserved domains, gene structures, chromosome location, and synteny were characterized. GRF7 expression varied among tissues and responded to diurnal rhythm. SsGRF7-YFP was localized preferentially in the nucleus and appears to act as a transcriptional cofactor. SsGRF7 positively regulated the size and length of rice leaves, possibly by regulating cell size and plant hormones. Of seven potential transcription factors binding to the SsGRF7 promoter in S. spontaneum, four showed positive expression patterns, and two showed negative expression patterns relative to SsGRF7.

Revealing the effects and mechanisms of arbuscular mycorrhizal fungi on manganese uptake and detoxification in Rhus chinensis

Arbuscular mycorrhizal fungi (AMF) can alleviate heavy metal phytotoxicity and promote plant growth, while the underlying mechanisms of AMF symbiosis with host plants under manganese (Mn) stress remain elusive. A pot experiment was carried out to investigate the plant growth, micro-structure, Mn accumulation, subcellular distribution, chemical forms, and physiological and biochemical response of Rhus chinensis inoculated with Funneliformis mosseae (FM) under different Mn treatments.The results showed that compared with plants without FM, FM-associated plants exhibited higher growth status, photosynthetic pigments, and photosynthesis under Mn stress. FM-associated plants were able to maintain greater integrity in mesophyll structure, higher thickness of leaf, upper epidermis, and lower epidermis under Mn treatment, and promote leaf growth. Mn accumulation in leaves (258.67–2230.50 mg kg−1), stems (132.67–1160.00 mg kg−1), and roots (360.92–2446.04 mg kg−1) of the seedlings inoculated with FM was higher than non-inoculated ones. FM-associated plants exhibited higher osmotic regulating substances and antioxidant enzymes’ activities under Mn exposure, suggesting lower Mn toxicity in FM inoculated seedlings, despite the augment in Mn accumulation. After FM inoculation, Mn concentration (151.04–1211.32 mg kg−1) and percentage (64.41–78.55%) enhanced in the cell wall, whilst the transport of Mn to aerial plant organs decreased. Furthermore, FM symbiosis favored the conversion of Mn from high toxic forms (2.17–15.68% in FEthanol, 11.37–24.52% in Fdeionized water) to inactive forms (28.30–38.15% in FNaCl, 18.07–28.59% in FHAc, 4.41–17.99% in FHCl) with low phytotoxicity. Our study offers a theoretical basis for remediation of the FM- R. chinensis symbiotic system in Mn-contaminated environments.

Overexpression of the Eucommia~ulmoides Aquaporin, EuPIP1;1, Promotes Leaf Growth, Flowering and Bolting, and Stress Tolerance in Arabidopsis.

Plasma membrane intrinsic protein (PIP) is one of the largest subfamilies of Aquaporins (AQPs) and plays an important role in plant growth and development, and resistance to abiotic stress. In this study, the full length of the EuPIP1;1 cDNA was cloned from Eucommia ulmoides using the rapid amplification of cDNA ends (RACE) method. The EuPIP1;1 gene was induced by drought treatment and expressed in all tested tissues, with the highest expression level in fruit. The subcellular localization showed that EuPIP1;1 was located in the plasma membrane. Constitutive overexpression of EuPIP1;1 in Arabidopsis thaliana could promote leaf growth and development, and accelerate bolting and flowering. Six genes related to growth and flowering (AtPIF4, AtTCP14, AtCRY1, AtCRY2, AtFCA and AtFT) were significantly up-regulated in transgenic lines. Further, EuPIP1;1 gene improved resistance to drought and salt stress in transgenic Arabidopsis. Under drought and salt stress treatment, the transgenic lines had a higher germination rate and accumulation of osmotic substances, lower membrane damage, and could maintain ion homeostasis. Our results suggest that EuPIP1;1 plays an essential role in plant growth and development and in the response to drought and salt stress.

Transcriptomic and metabolomic reveals silicon enhances adaptation of rice under dry cultivation by improving flavonoid biosynthesis, osmoregulation, and photosynthesis.

Dry cultivation is a new rice crop mode used to alleviate water shortage and develop water-saving agriculture. There is obvious genetic difference compared with drought-tolerant rice. Silicon (Si) plays an important role in plant adaptation to adverse environmental conditions and can significantly improve the drought tolerance and yield of rice. However, the regulatory mechanism via which Si provides plant tolerance or adaptation under dry cultivation is not well understood. The present study investigated the changes in plant growth, photosynthetic gas exchange, and oxidative stress of the rice cultivar “Suijing 18” under dry cultivation. Si improved photosynthetic performance and antioxidant enzyme activity and subsequently reduced lipid peroxidation of rice seedlings, promoted LAI and promoted leaf growth under dry cultivation. Further, transcriptomics combined with quasi-targeted metabolomics detected 1416 and 520 differentially expressed genes (DEGs), 38 and 41 differentially accumulated metabolites (DAMs) in the rice leaves and roots, respectively. Among them, 13 DEGs were involved in flavonoid biosynthesis, promoting the accumulation of flavonoids, anthocyanins, and flavonols in the roots and leaves of rice under dry cultivation. Meanwhile, 14 DEGs were involved in photosynthesis, promoting photosystem I and photosystem II responses, increasing the abundance of metabolites in leaves. On the other hand, 24 DAMs were identified involved in osmoregulatory processes, significantly increasing amino acids and carbohydrates and their derivatives in roots. These results provide new insight into the role of Si in alleviating to adverse environmental, Si enhanced the accumulation of flavonoids and osmoregulatory metabolites, thereby alleviating drought effect on the roots. On the other hand, improving dehydration resistance of leaves, guaranteeing normal photosynthesis and downward transport of organic matter. In conclusion, Si promoted the coordinated action between the above-ground and below-ground plant parts, improved the root/shoot ratio (R/S) of rice and increased the sugar content and enhancing rice adaptability under dry cultivation conditions. The establishment of the system for increasing the yield of rice under dry cultivation provides theoretical and technical support thereby promoting the rapid development of rice in Northeast China, and ensuring national food security.

Adjusting leaf nitrogen allocation could promote photosynthetic capacity, and nitrogen accumulation in Cucumis sativus L.

Nitrogen (N) is essential for crop growth and development under stress. The photosynthetic capacity of crops depends on the leaf N content (N a ), and leaf N allocation is an important factor affecting net photosynthetic rate (P n ). However, the relationship between N supply and leaf N allocation and the effects of different N forms on cucumber growth at low-temperature (LT) stress are still unclear. In this study, the effects of different N concentrations (NC) and ammonium (NH 4 + )-nitrate (NO 3 − ) ratios (A-NR) supplied to grown LT-stressed cucumber at seedling and flowering to early fruiting stages on growth, photosynthesis, N accumulation, and leaf N allocation were assessed. NC, A-NR, and their interactions significantly affected leaf area, P n , chlorophyll content, and N accumulation at seedling and flowering to early fruiting stages. When the cucumber plants were grown in LT environment, the maximum photochemical efficiency, leaf area, P n , chlorophyll content, N a , water-soluble proteins N (N w ), and N accumulations in various organs were the greatest. The content of sodium dodecyl sulfate (a detergent) soluble protein N (N s ) was minimal when the NCs at the seedling and flowering to early fruiting stages were 10.5 and 28 mmol·L −1 , respectively, and the A-NRs were both 1:1. Correlation analysis showed that leaf area, P n , chlorophyll content, and N accumulation could be improved by increasing Na and N w or reducing N s . This finding suggested that increasing NC and NH 4 + proportion in the nutrient solution could increase N a and N w in leaves and reduce the content of N s , thereby improving photosynthetic capacity to promote leaf growth and increasing cucumber LT resistance. • NC, A-NR and their interactions significantly affected cucumber growth under low temperature stress. • N applied increases leaf N content mainly due to the increase in water-soluble protein N content. • Increasing N w content and reducing N s content could improve photosynthetic capacity of cucumber.

Shortening the Vegetative Growth Stage of Phalaenopsis Queen Beer ‘Mantefon’ by Controlling Light with Calcium Ammonium Nitrate Levels under Enriched CO2

The vegetative growth, photosynthetic, and stomatal characteristics were investigated in Phalaenopsis Queen Beer ‘Mantefon’ to determine light’s influence with calcium ammonium nitrate (CAN) levels under 800 μmol·mol−1 CO2. Two lights (150 ± 20 and 300 ± 20 μmol·m−2·s−1) and CAN levels were employed for 40 weeks: calcium, ammonium, and nitrate levels by 0.90, 0.55, and 2.97 mmol·L−1 (CAN1), 8.63, 1.11, and 6.05 mmol·L−1 (CAN2), 12.80, 1.72, and 9.13 mmol·L−1 (CAN3), and 18.80, 2.27, and 12.20 mmol·L−1 (CAN4), respectively. The number of leaves increased in the plants grown at 300 ± 20 μmol·m−2·s−1 with CAN1 compared to control. Plants grown at 300 ± 20 μmol·m−2·s−1 with CAN4 had the lowest number of leaves among all plants. The time to the mature leaf span decreased in the plants grown at 300 ± 20 μmol·m−2·s−1 with CAN1. The net CO2 uptake was higher in the plants grown at 300 ± 20 μmol·m−2·s−1 than those grown at 150 ± 20 μmol·m−2·s−1 with CAN1–3 conditions. The water-use efficiency is higher in the plants grown with CAN1 than those with CAN2–4 at 300 ± 20 μmol·m−2·s−1. The maximum stomatal aperture was the largest in the plants grown at 300 ± 20 μmol·m−2·s−1 with CAN1–2 among all plants. Consequently, light levels of 300 ± 20 μmol·m−2·s−1 in Phalaenopsis Queen Beer ‘Mantefon’ must be accompanied by nutrient CAN1 to improve photosynthesis and stomatal activity and promote leaf growth under 800 μmol·mol−1 CO2 conditions.

The roles of cadmium on growth of seedlings by analysing the composition of metabolites in pumpkin tissues

Changes in the types and contents of metabolites in plants can occur in response to environmental stress. In this study, pumpkin seeds were cultivated in a cadmium ion solution (cadmium sulfate) for 7 days, and growth parameters, antioxidant enzyme activities, and metabolites in the root, stem, and leaf were analyzed. The results showed that cadmium accumulation characteristics were in the order of root > stem > leaf. Cadmium restrained root growth and promoted superoxide dismutase, peroxidase, catalase activities in the root, but inhibited their activities in the leaf. Cadmium did not change the total biomass of pumpkin seedlings. Orthogonal partial least squares (OPLS) analyses were conducted to detect the relationships between fresh weight and metabolites. These analyses revealed that maltose had significantly positive relationships with the fresh weight of the root, stem, and leaf. Cadmium influenced glyoxylate and dicarboxylate metabolism, aminoacyl-tRNA biosynthesis, sulfur metabolism, butanoate metabolism, alanine, aspartate and glutamate metabolism, glutathione metabolism, glycine, serine and threonine metabolism in the root; glycolysis/gluconeogenesis in the stem; and biosynthesis of unsaturated fatty acids, galactose metabolism, cutin, suberine and wax biosynthesis in the leaf. It is important that cadmium inhibited root growth by inhibiting carbohydrate transport from the leaf to the root and promoted leaf growth by the accumulation of carbohydrates in the leaf. Furthermore, cadmium also restrained amino acid metabolism in the root of pumpkin seedlings. These results provide new information about how pumpkin seedlings respond to cadmium stress.

Single-cell RNA-seq describes the transcriptome landscape and identifies critical transcription factors in the leaf blade of the allotetraploid peanut (Arachis hypogaea L.).

SummarySingle‐cell RNA‐seq (scRNA‐seq) has been highlighted as a powerful tool for the description of human cell transcriptome, but the technology has not been broadly applied in plant cells. Herein, we describe the successful development of a robust protoplast cell isolation system in the peanut leaf. A total of 6,815 single cells were divided into eight cell clusters based on reported marker genes by applying scRNA‐seq. Further, a pseudo‐time analysis was used to describe the developmental trajectory and interaction network of transcription factors (TFs) of distinct cell types during leaf growth. The trajectory enabled re‐investigation of the primordium‐driven development processes of the mesophyll and epidermis. These results suggest that palisade cells likely differentiate into spongy cells, while the epidermal cells originated earlier than the primordium. Subsequently, the developed method integrated multiple technologies to efficiently validate the scRNA‐seq result in a homogenous cell population. The expression levels of several TFs were strongly correlated with epidermal ontogeny in accordance with obtained scRNA‐seq values. Additionally, peanut AHL23 (AT‐HOOK MOTIF NUCLEAR LOCALIZED PROTEIN 23), which is localized in nucleus, promoted leaf growth when ectopically expressed in Arabidopsis by modulating the phytohormone pathway. Together, our study displays that application of scRNA‐seq can provide new hypotheses regarding cell differentiation in the leaf blade of Arachis hypogaea. We believe that this approach will enable significant advances in the functional study of leaf blade cells in the allotetraploid peanut and other plant species.

The Cytokinin Status of the Epidermis Regulates Aspects of Vegetative and Reproductive Development in Arabidopsis thaliana.

The epidermal cell layer of plants has important functions in regulating plant growth and development. We have studied the impact of an altered epidermal cytokinin metabolism on Arabidopsis shoot development. Increased epidermal cytokinin synthesis or breakdown was achieved through expression of the cytokinin synthesis gene LOG4 and the cytokinin-degrading CKX1 gene, respectively, under the control of the epidermis-specific AtML1 promoter. During vegetative growth, increased epidermal cytokinin production caused an increased size of the shoot apical meristem and promoted earlier flowering. Leaves became larger and the shoots showed an earlier juvenile-to-adult transition. An increased cytokinin breakdown had the opposite effect on these phenotypic traits indicating that epidermal cytokinin metabolism can be a factor regulating these aspects of shoot development. The phenotypic consequences of abbreviated cytokinin signaling in the epidermis achieved through expression of the ARR1-SRDX repressor were generally milder or even absent indicating that the epidermal cytokinin acts, at least in part, cell non-autonomously. Enhanced epidermal cytokinin synthesis delayed cell differentiation during leaf development leading to an increased cell proliferation and leaf growth. Genetic analysis showed that this cytokinin activity was mediated mainly by the AHK3 receptor and the transcription factor ARR1. We also demonstrate that epidermal cytokinin promotes leaf growth in a largely cell-autonomous fashion. Increased cytokinin synthesis in the outer layer of reproductive tissues and in the placenta enhanced ovule formation by the placenta and caused the formation of larger siliques. This led to a higher number of seeds in larger pods resulting in an increased seed yield per plant. Collectively, the results provide evidence that the cytokinin metabolism in the epidermis is a relevant parameter determining vegetative and reproductive plant growth and development.

Growth‐regulating factor 5 (GRF5)‐mediated gene regulatory network promotes leaf growth and expansion in poplar

Summary Although polyploid plants have larger leaves than their diploid counterparts, the molecular mechanisms underlying this difference (or trait) remain elusive.Differentially expressed genes (DEGs) between triploid and full‐sib diploid poplar trees were identified from two transcriptomic data sets followed by a gene association study among DEGs to identify key leaf growth regulators. Yeast one‐hybrid system, electrophoretic mobility shift assay, and dual‐luciferase assay were employed to substantiate that PpnGRF5‐1 directly regulated PpnCKX1. The interactions between PpnGRF5‐1 and growth‐regulating factor (GRF)‐interacting factors (GIFs) were experimentally validated and a multilayered hierarchical regulatory network (ML‐hGRN)‐mediated by PpnGRF5‐1 was constructed with top‐down graphic Gaussian model (GGM) algorithm by combining RNA‐sequencing data from its overexpression lines and DAP‐sequencing data.PpnGRF5‐1 is a negative regulator of PpnCKX1. Overexpression of PpnGRF5‐1 in diploid transgenic lines resulted in larger leaves resembling those of triploids, and significantly increased zeatin and isopentenyladenine in the apical buds and third leaves. PpnGRF5‐1 also interacted with GIFs to increase its regulatory diversity and capacity. An ML‐hGRN‐mediated by PpnGRF5‐1 was obtained and could largely elucidate larger leaves.PpnGRF5‐1 and the ML‐hGRN‐mediated by PpnGRF5‐1 were underlying the leaf growth and development.

Effects of different integration of water and fertilizer modes on the absorption and utilization of nitrogen fertilizer and fruit yield and quality of apple trees

We examined nitrogen use efficiency of 15N-urea of 15-year-old 'Gala' apple trees by broadcast fertilization (T1), nitrogen fertilization with drip irrigation (T2) and nitrogen fertilization with subsurface irrigation (T3), to further improve the water and fertilizer integration technology for apple orchard and to improve nitrogen utilization efficiency. The results showed that leaf area, chlorophyll, and leaf nitrogen content of leaves were significantly higher in T3 treatment than those in T1 and T2 treatments. Soil mineral nitrogen content (20-40 cm) in each period followed the order of T3>T2>T1, while that in 0-20 cm followed an order of T2>T3>T1. The Ndff value at organ level (the contribution rate of the 15N amount absorbed by various organs of the tree to the total nitrogen content of the organ) was the highest in T3 treatment in each period, followed by T2 and T1 treatments. The utilization rate of 15N in the fruit ripening period followed an order of T3>T2>T1. The 15N utilization rate of T3 reached 24.2%, being 1.19 and 1.65 times of T2 and T1, respectively. The 15N distribution rate in the fruits during the fruit maturity stage was the highest in T1 treatment, while that in the storage organs was the highest in T2 treatment and that in the reproduction organs was the highest in T3 treatment. The single fruit weight, yield, soluble solids, hardness, soluble sugar and sugar-acid ratio were the highest in T3 treatment, followed by T2 and T1 treatments. In summary, nitrogen application by percolation irrigation (subsurface application) significantly promoted leaf growth and nitrogen utilization of apple tree, and improved fruit yield and quality.

Ectopic expression of the persimmon β-galactosidase gene DkGAL2 promotes leaf growth, delays dark-induced senescence and enhances tolerance to abiotic stress in Arabidopsis

Plant β-galactosidases (EC 3.2.1.23) have activities related to cell wall galactan-containing polysaccharides metabolism and cell wall remodeling, though their precise functions have not yet been established. We previously isolated a persimmon β-galactosidase gene, DkGAL2, with high levels of transcripts were detected in leaves and during fruit developments. Here, abundant DkGAL2 transcripts were observed in expanding persimmon leaves, increasing with dark-induced senescence but remaining constant with glucose supplementation under dark conditions. The promoter sequence of DkGAL2 harbors several cis-elements related to leaf expansion. To further investigate the role of DkGAL2, ectopic overexpression of DkGAL2 in Arabidopsis was performed, and the leaves of DkGAL2-overexpressing plants exhibited high growth rates and large leaf areas. Moreover, DkGAL2 overexpression enhanced tolerance to abscisic acid (ABA), methyl jasmonate (MeJA) and NaCl, with plants have long root lengths and high galactose contents, suggesting a role for DkGAL2 in abiotic stress responses. In addition, DkGAL2-transgenic plants showed delayed senescence under dark conditions, and some ABA signaling-related genes were significantly suppressed in transgenic plants during senescence compared to WT plants. Together, these results demonstrate that by affecting cell wall modification, DkGAL2 is involved in leaf expansion and senescence. The functions of DkGAL2 might affect ABA signaling during senescence.

Glycosyltransferase OsUGT90A1 helps protect the plasma membrane during chilling stress in rice.

Due to its subtropical origins, rice (Oryza sativa) is sensitive to low-temperature stress. In this study, we identify LOC_Os04g24110, annotated to encode the UDP-glycosyltransferase enzyme UGT90A1, as a gene associated with the low-temperature seedling survivability (LTSS) quantitative trait locus qLTSS4-1. Differences between haplotypes in the control region of OsUGT90A1 correlate with chilling tolerance phenotypes, and reflect differential expression between tolerant and sensitive accessions rather than differences in protein sequences. Expression of OsUGT90A1 is initially enhanced by low temperature, and its overexpression helps to maintain membrane integrity during cold stress and promotes leaf growth during stress recovery, which are correlated with reduced levels of reactive oxygen species due to increased activities of antioxidant enzymes. In addition, overexpression of OsUGT90A1 in Arabidopsis improves freezing survival and tolerance to salt stress, again correlated with enhanced activities of antioxidant enzymes. Overexpression of OsUGT90A1 in rice decreases root lengths in 3-week-old seedlings while gene-knockout increases the length, indicating that its differential expression may affect phytohormone activities. We conclude that higher OsUGT90A1 expression in chilling-tolerant accessions helps to maintain cell membrane integrity as an abiotic stress-tolerance mechanism that prepares plants for the resumption of growth and development during subsequent stress recovery.

Identification of TCP13 as an Upstream Regulator of ATHB12 during Leaf Development.

Leaves grow by distinct phases controlled by gene regulatory networks including many transcription factors. Arabidopsis thaliana homeobox 12 (ATHB12) promotes leaf growth especially during the cell expansion phase. In this study, we identify TCP13, a member of the TCP transcription factor family, as an upstream inhibitor of ATHB12. Yeast one-hybrid screening using a 1.2-kb upstream region of ATHB12 resulted in the isolation of TCP13 as well as other transcription factors. Transgenic plants constitutively expressing TCP13 displays a significant reduction in leaf cell size especially during the cell expansion period, while repression of TCP13 and its paralogs (TCP5 and TCP17) result in enlarged leaf cells, indicating that TCP13 and its paralogs inhibit leaf development, mainly at the cell expansion phase. Its expression pattern during leaf expansion phase is opposite to ATHB12 expression. Consistently, the expression of ATHB12 and its downstream genes decreases when TCP13 was overexpressed, and increases when the expression of TCP13 and its paralogs is repressed. In chromatin immunoprecipitation assays using TCP13-GFP plants, a fragment of the ATHB12 upstream region that contains the consensus sequence for TCP binding is strongly enriched. Taken together, these findings indicate that TCP13 and its paralogs inhibit leaf growth by repressing ATHB12 expression.

Dry Season Irrigation Promotes Leaf Growth in Eucalyptus urophylla × E. grandis under Fertilization

Leaves are essential for photosynthesis and gas exchange, and their growth characteristics are the key factors that influence the carbon budget. Eucalyptus is widely afforested in south China due to its fast-growing and high-yield features. Water and fertilizer are the main factors affecting plant growth. Studying the effects of different water and fertilizer treatments on the growth of Eucalyptus leaves under seasonal drought could further elucidate the optimal additions for Eucalyptus productivity. In this study, we investigated the leaf area, length, width, perimeter, and expansion rates of the commercial species E. urophylla × E. grandis under different treatments of dry season irrigation and fertilizer application to elucidate the growth dynamics of the leaves. The results indicated that both dry season irrigation and fertilizer could affect whole leaf expansion. Leaf area was largest when water and fertilizer were added at the same time. In this experiment, we found that fertilization had a significant effect on the leaf shape index of the Eucalyptus leaves. The leaf shape index was larger with the fertilizer treatment, which made the leaves slender. Dry season irrigation shorten the peak period of leaf growth and increase the leaf area. Our results help to further understand the mechanism of Eucalyptus productivity under seasonal drought and provide theoretical support for Eucalyptus production.

Trans-Cinnamic acid-induced leaf expansion involves an auxin-independent component

ABSTRACTThe phenylpropanoid pathway, the source of a large array of compounds with diverse functions, starts with the synthesis of trans-cinnamic acid (t-CA) that is converted by cinnamate-4-hydroxylase (C4H) into p-coumaric acid. We have recently shown that in Arabidopsis, exogenous t-CA promotes leaf growth by increasing cell expansion and that this response requires auxin signaling. We have also shown that cell expansion is increased in C4H loss-of-function mutants. Here we provide further evidence that leaf growth is enhanced by either t-CA or a t-CA derivative that accumulates upstream of C4H. We also show that this growth response pathway has two components: one that requires auxin signaling and another which employs a currently unknown mechanism.

Effects of light quality on leaf senescence and endogenous hormones content in grapevine under protected cultivation

Two grape varieties 'Italia' and 'Centenial seedless' cultured in protected and delayed cultivation were used as experimental materials to study the effects of red and blue light quality on chlorophyll content, net photosynthetic rate, and endogenous hormone content during leaf senescence. The results showed that the chlorophyll content and net photosynthetic rate of the grapes were significantly enhanced in the red light treatment. Although the content of endogenous GA3 was decreased, an increase in abscisic acid (ABA) content and a decrease of total content of zeaxanthin (ZR) were obviously slowed, which led to the significant increase in value of (GA3+ZR)/ABA, delaying leaf senescence. In prophase of leaf senescence, the chlorophyll contents, net photosynthetic rate and (GA3+ZR)/ABA of the grapes were lower in the blue light treatment than those in the control, and the leaf senescence in the blue light treatment was accelerated. At late stage of leaf senescence, the chlorophyll content, net photosynthetic rate and (GA3+ZR)/ABA in the blue light treatment were gradually higher than those in the control, and the leaf senescence was delayed to a certain extent. The plant endogenous hormone auxin (IAA) promoted leaf growth and development in prophase of leaf senescence and accelerated leaf aging in late stage of leaf senescence. The leaf senescence rate of 'Italia' was slower than that of 'Centenial seedless'. In conclusion, our experiment suggested that red light was the best on delaying leaf senescence and prolonging the functional period of leaves.

Effects of Nitrogen and the Various Forms of Nitrogen on Phalaenopsis Orchid—A Review

Growers realize the importance of nitrogen (N) on the vegetative growth of phalaenopsis orchids (hybrids of Phalaenopsis sp.), but often overlook its influence on reproductive growth. Low N may result in slow plant growth, pale-green leaves, abscission of lower leaves, and few flowers in phalaenopsis. Increasing N concentration up to 200 mg·L−1 promotes leaf growth and increases flower count. High N concentration promotes lateral branching on the flowering stalk, thereby greatly increasing the total flower count and elevating the commercial value. It is important that N be continually applied during the forcing period for best flowering performance, particularly for those that had undergone international shipping. For the vegetative phalaenopsis plants that are induced to flower without being shipped internationally, the N that is already in the plant before spiking provides 43% and the N being absorbed by roots after cooling provides 57% of the total N in the inflorescence at time of visible bud. When insufficiently fertilized or no fertilization is applied during the forcing period, more of the existing N in a plant is mobilized for inflorescence development. Phalaenopsis roots can take up all three forms of N [i.e., nitrate (NO3-N), ammonium (NH4-N), and urea] directly. In two studies, phalaenopsis plants were supplied with the same amount of total N but with varying NO3-N from 100%, 75%, 50%, 25%, to 0% (a common N concentration was achieved by the substitution of the respective balance with NH4-N). Plants were smaller when receiving 75% or 100% NH4-N with a tendency of decreasing top leaf width and whole-plant leaf spread as NO3-N decreased from 100% to 0%. Spiking was delayed and spiking rate decreased when plants were grown in sphagnum moss, but not a bark mix, and received more than 50% of the N in NH4-N. As the ratio between NO3-N and NH4-N increased, flowers became increasingly larger. The negative effects of low ratios of NO3-N to NH4-N were more severe in the second flowering cycle. When supplied with 50% or more NH4-N, the absorption of cations by phalaenopsis roots declined, with reduced concentrations of calcium and magnesium in plants, while symptoms of ammonium toxicity appeared, including growth retardation, chlorotic leaves, and necrotic roots. In conclusion, adequate N and its continual supply during both vegetative and reproductive stages are recommended for the best growth and flowering of phalaenopsis. Since phalaenopsis plants prefer N in the NO3-N form, it is suggested that growers choose and apply a fertilizer with nitrate as the major N source.

An RNA-Seq Analysis of Grape Plantlets Grown in vitro Reveals Different Responses to Blue, Green, Red LED Light, and White Fluorescent Light

Using an RNA sequencing (RNA-seq) approach, we analyzed the differentially expressed genes (DEGs) and physiological behaviors of “Manicure Finger” grape plantlets grown in vitro under white, blue, green, and red light. A total of 670, 1601, and 746 DEGs were identified in plants exposed to blue, green, and red light, respectively, compared to the control (white light). By comparing the gene expression patterns with the growth and physiological responses of the grape plantlets, we were able to link the responses of the plants to light of different spectral wavelengths and the expression of particular sets of genes. Exposure to red and green light primarily triggered responses associated with the shade-avoidance syndrome (SAS), such as enhanced elongation of stems, reduced investment in leaf growth, and decreased chlorophyll levels accompanied by the expression of genes encoding histone H3, auxin repressed protein, xyloglucan endotransglycosylase/hydrolase, the ELIP protein, and microtubule proteins. Furthermore, specific light treatments were associated with the expression of a large number of genes, including those involved in the glucan metabolic pathway and the starch and sucrose metabolic pathways; these genes were up/down-regulated in ways that may explain the increase in the starch, sucrose, and total sugar contents in the plants. Moreover, the enhanced root growth and up-regulation of the expression of defense genes accompanied with SAS after exposure to red and green light may be related to the addition of 30 g/L sucrose to the culture medium of plantlets grown in vitro. In contrast, blue light induced the up-regulation of genes related to microtubules, serine carboxypeptidase, chlorophyll synthesis, and sugar degradation and the down-regulation of auxin-repressed protein as well as a large number of resistance-related genes that may promote leaf growth, improve chlorophyll synthesis and chloroplast development, increase the ratio of chlorophyll a (chla)/chlorophyll b (chlb), and decrease the ratio of carbohydrates to proteins in plants. Although exposure to red and green light seems to impose “shade stress” on the plantlets, growth under blue light is comparable to growth observed under white or broad-spectrum light.