Stages Of Panicle Development Research Articles

Nitrogen fertilization application strategies improve yield of the rice cultivars with different yield types by regulating phytohormones

Rice (Oryza sativa L.) is the most important food crop worldwide, and its sustainable development is essential to ensure global food security. Panicle morphological and physiological characteristics plays an important role in rice yield formation. However, under different nitrogen (N) fertilization strategies, it is not clear whether the morphological and physiological state of panicles at panicle development stage affects the formation of yield. To understand how the panicle differentiation and development, and grain yield are affected by the N fertilization strategies, and clarify the relationship between related traits and yield in the process of panicle development in different cultivars. In this study consisted of no N fertilizer and four N fertilization strategies, a panicle weight type (PWT) rice cultivar, Dongfu 114 (DF114) and a panicle number type (PNT) rice cultivar, Longdao 11 (LD11) were grown in the field. The results showed that N fertilization strategies could improve the nitrogen use efficiency and yield of rice, but the response of different rice varieties to N fertilizer strategies was different. Different from the DF114, the further increase of panicle N fertilizer ratio could not further improve the yield of LD11, and the highest grain yield of DF114 and LD11 was obtained under N4 and N3 conditions, respectively. In addition, this study found that N fertilizer strategies can affect the content of phytohormones in rice at the panicle differentiation stage, and then regulate the differentiation and development of rice panicles to affect yield. It is of great significance to optimize the application mode of N fertilizer according to the characteristics of varieties to improve rice yield and ensure food security.

Panicle Apical Abortion 7 Regulates Panicle Development in Rice (Oryza sativa L.).

The number of grains per panicle significantly contributes to rice yield, but the regulatory mechanism remains largely unknown. Here, we reported a loss-of-function mutant, panicle apical abortion 7 (paa7), which exhibited panicle abortion and degeneration of spikelets on the apical panicles during the late stage of young panicle development in rice. High accumulations of H2O2 in paa7 caused programmed cell death (PCD) accompanied by nuclear DNA fragmentation in the apical spikelets. Map-based cloning revealed that the 3 bp “AGC” insertion and 4 bp “TCTC” deletion mutation of paa7 were located in the 3′-UTR regions of LOC_Os07g47330, which was confirmed through complementary assays and overexpressed lines. Interestingly, LOC_Os07g47330 is known as FRIZZY PANICLE (FZP). Thus, PAA7 could be a novel allele of FZP. Moreover, the severe damage for panicle phenotype in paa7/lax2 double mutant indicated that PAA7 could crosstalk with Lax Panicle 2 (LAX2). These findings suggest that PAA7 regulates the development of apical spikelets and interacts with LAX2 to regulate panicle development in rice.

Phytohormones and Transcriptome Analyses Revealed the Dynamics Involved in Spikelet Abortion and Inflorescence Development in Rice.

Panicle degeneration, sometimes known as abortion, causes heavy losses in grain yield. However, the mechanism of naturally occurring panicle abortion is still elusive. In a previous study, we characterized a mutant, apical panicle abortion1331 (apa1331), exhibiting abortion in apical spikelets starting from the 6 cm stage of panicle development. In this study, we have quantified the five phytohormones, gibberellins (GA), auxins (IAA), abscisic acid (ABA), cytokinins (CTK), and brassinosteroids (BR), in the lower, middle, and upper parts of apa1331 and compared these with those exhibited in its wild type (WT). In apa331, the lower and middle parts of the panicle showed contrasting concentrations of all studied phytohormones, but highly significant changes in IAA and ABA, compared to the upper part of the panicle. A comparative transcriptome of apa1331 and WT apical spikelets was performed to explore genes causing the physiological basis of spikelet abortion. The differential expression analysis revealed a significant downregulation and upregulation of 1587 and 978 genes, respectively. Hierarchical clustering of differentially expressed genes (DEGs) revealed the correlation of gene ontology (GO) terms associated with antioxidant activity, peroxidase activity, and oxidoreductase activity. KEGG pathway analysis using parametric gene set enrichment analysis (PGSEA) revealed the downregulation of the biological processes, including cell wall polysaccharides and fatty acids derivatives, in apa1331 compared to its WT. Based on fold change (FC) value and high variation in expression during late inflorescence, early inflorescence, and antherdevelopment, we predicted a list of novel genes, which presumably can be the potential targets of inflorescence development. Our study not only provides novel insights into the role of the physiological dynamics involved in panicle abortion, but also highlights the potential targets involved in reproductive development.

Systematic Analysis of NB-ARC Gene Family in Rice and Functional Characterization of GNP12

The NB-ARC (nucleotide-binding adaptor shared by APAF-1, R proteins, and CED-4) gene family plays a critical role in plant development. However, our understanding of the mechanisms of how NB-ARC genes regulate plant development in the plant panicle is still limited. Here, we subjected 258 NB-ARC genes in rice to genome-wide analysis to characterize their structure, function, and expression patterns. The NB-ARC genes were classified into three major groups, and group II included nine subgroups. Evolutionary analysis of NB-ARC genes in a dicotyledon plant (Arabidopsis thaliana) and two monocotyledonous plants (Oryza sativa L. and Triticum aestivum) indicated that homologous genome segments were conserved in monocotyledons and subjected to weak positive selective pressure during evolution. Dispersed and proximal replication events were detected. Expression analysis showed expression of most NB-ARC genes in roots, panicles, and leaves, and regulation at the panicle development stage in rice Ce253. The GNP12 gene encodes RGH1A protein, which regulates rice yield according to panicle length, grain number of panicle, and grain length, with eight major haplotypes. Most members of NB-ARC protein family are predicted to contain P-loop conserved domains and localize on the membrane. The results of this study will provide insight into the characteristics and evolution of NB-ARC family and suggest that GNP12 positively regulates panicle development.

Response of Senegalese Sorghum Seedlings to Pathotype 5 of Sporisorium reilianum

Sporisorium reilianum causes head smut in sorghum. A total of 36 Senegalese sorghum accessions comprised of sorghum lines that have not been explored with response to pathotype 5 of S. reilianum were evaluated with 3 different treatments. First, seedling shoots were inoculated while still in soil with teliospores in agar, and then submerged under water at 4 days post inoculation. Signs of infection (noticeable spots) on the first leaf were observed up to 6 days post submergence. Second, seedlings at the same stage were inoculated by placing the teliospore impregnated agar around the stem in pots, moved to a greenhouse and grown to full panicle development stage. Third, seedings were inoculated via syringe inoculation in the greenhouse. Although soil inoculated seedlings grown in the greenhouse did not result in systemic infection as determined by lack of symptoms at panicle exsertion, 88.9% of tested cultivars showed systemic infections when syringe inoculated in the greenhouse. Inoculation of seedlings maintained under water led to broad range of noticeable spots that are assumed to be potential infection sites based on a previous study. In addition, seedling inoculation led to slightly upregulated expression of chitinase and PR10, genes that are associated with defense in aerial parts of plants.

Understanding the Influences of Rice Starch Fine Structure and Protein Content on Cooked Rice Texture

AbstractAmylose content, fine structure, and protein content affect the hardness and stickiness of cooked rice. However, the mechanisms of those effects have not been fully understood especially the fine structure of amylose. Here, 22 rice varieties with large ranges of both starch chain‐length distributions and protein content are examined, and the starch structural results are parameterized using biosynthesis‐based models. The ratios of the activities of branching enzyme and starch synthase for amylose showed positive and negative correlations with rice hardness (coefficient 0.556 and 0.838) and stickiness (coefficient −0.498 and −0.639), respectively. Protein content is strongly positively correlated with hardness, with nitrogen application up to the panicle development stage (coefficient 0.640). New findings could be obtained from these correlations, which reveal that in the whole region of amylose, the shorter the amylose is, the harder and less sticky the cooked rice is, which has not been reported previously. In addition, protein is found to influence rice hardness significantly, while rice stickiness is less affected by it. Therefore, a comprehensive mechanism of protein effects on rice texture is proposed. This work provides information for breeders to develop improved rice varieties.

Comparative metabolomic and transcriptomic analysis reveals a coexpression network of the carotenoid metabolism pathway in the panicle of Setaria italica

BackgroundThe grains of foxtail millet are enriched in carotenoids, which endow this plant with a yellow color and extremely high nutritional value. However, the underlying molecular regulation mechanism and gene coexpression network remain unclear.MethodsThe carotenoid species and content were detected by HPLC for two foxtail millet varieties at three panicle development stages. Based on a homologous sequence BLAST analysis, these genes related to carotenoid metabolism were identified from the foxtail millet genome database. The conserved protein domains, chromosome locations, gene structures and phylogenetic trees were analyzed using bioinformatics tools. RNA-seq was performed for these samples to identify differentially expressed genes (DEGs). A Pearson correlation analysis was performed between the expression of genes related to carotenoid metabolism and the content of carotenoid metabolites. Furthermore, the expression levels of the key DEGs were verified by qRT-PCR. The gene coexpression network was constructed by a weighted gene coexpression network analysis (WGCNA).ResultThe major carotenoid metabolites in the panicles of DHD and JG21 were lutein and β-carotene. These carotenoid metabolite contents sharply decreased during the panicle development stage. The lutein and β-carotene contents were highest at the S1 stage of DHD, with values of 11.474 μg /100 mg and 12.524 μg /100 mg, respectively. Fifty-four genes related to carotenoid metabolism were identified in the foxtail millet genome. Cis-acting element analysis showed that these gene promoters mainly contain ‘plant hormone’, ‘drought stress resistance’, ‘MYB binding site’, ‘endosperm specific’ and ‘seed specific’ cis-acting elements and especially the ‘light-responsive’ and ‘ABA-responsive’ elements. In the carotenoid metabolic pathways, SiHDS, SiHMGS3, SiPDS and SiNCED1 were more highly expressed in the panicle of foxtail millet. The expression of SiCMT, SiAACT3, SiPSY1, SiZEP1/2, and SiCCD8c/8d was significantly correlated with the lutein content. The expression of SiCMT, SiHDR, SiIDI2, SiAACT3, SiPSY1, and SiZEP1/2 was significantly correlated with the content of β-carotene. WGCNA showed that the coral module was highly correlated with lutein and β-carotene, and 13 structural genes from the carotenoid biosynthetic pathway were identified. Network visualization revealed 25 intramodular hub genes that putatively control carotenoid metabolism.ConclusionBased on the integrative analysis of the transcriptomics and carotenoid metabonomics, we found that DEGs related to carotenoid metabolism had a stronger correlation with the key carotenoid metabolite content. The correlation analysis and WGCNA identified and predicted the gene regulation network related to carotenoid metabolism. These results lay the foundation for exploring the key target genes regulating carotenoid metabolism flux in the panicle of foxtail millet. We hope that these target genes could be used to genetically modify millet to enhance the carotenoid content in the future.

Functional Diversification of euANT/PLT Genes in Oryza sativa Panicle Architecture Determination.

Grain yield, which is one of the most important traits in rice breeding, is controlled in part by panicle branching patterns. Numerous genes involved in the control of panicle architecture have been identified through mutant and QTL characterization. Previous studies suggested the importance of several AP2/ERF transcription factor-encoding genes in the control of panicle development, including the AINTEGUMENTA/PLETHORA-like (euANT/PLT) genes. The ANT gene was specifically considered to be a key regulator of shoot and floral development in Arabidopsis thaliana. However, the likely importance of paralogous euANT/PLT genes in the regulation of meristem identities and activities during panicle architecture development has not to date been fully addressed in rice. In this study, we observed that the rice euANT/PLT genes displayed divergent temporal expression patterns during the branching stages of early panicle development, with spatial localization of expression in meristems for two of these genes. Moreover, a functional analysis of rice ANT-related genes using genome editing revealed their importance in the control of panicle architecture, through the regulation of axillary meristem (AM) establishment and meristem fate transition. Our study suggests that the paralogous euANT/PLT genes have become partially diversified in their functions, with certain opposing effects, since they arose from ancestral gene duplication events, and that they act in regulating the branching of the rice panicle.

Folate metabolic profiling and expression of folate metabolism-related genes during panicle development in foxtail millet (Setaria italica (L.) P. Beauv).

Foxtail millet grain has higher folate content than other cereal crops. However, the folate metabolite content and the expression patterns of folate metabolite-related genes are unknown. Liquid chromatography-mass spectrometry was used to investigate 12 folate metabolites in a foxtail millet panicle. The content of total folate and derivatives gradually decreased during panicle development. Polyglutamate 5-formyl-tetrahydrofolate was the major form. Twenty-eight genes involved in the folate metabolic pathway were identified through bioinformatic analysis. These genes in Setaria italica, S. viridis and Zea mays showed genomic collinearity. Phylogenetic analysis revealed that the folate-related genes were closely related among the C4 plants compared to C3 plants. The gene expressions were then studied at three panicle development stages. The gene expression patterns were classified into two groups, namely SiADCL1 and SiGGH as two key enzymes, which are responsible for folate synthesis and degradation; their expression levels were highest at the early panicle development stage, up to 179.11- and 163.88-fold, respectively. Their expression levels had a similar downward trend during panicle development and were significantly positively correlated with the concentration of total folate and folate derivatives. However, SiSHMT3 expression levels were significantly negatively correlated with total folate concentration. Besides being the major determinants of folate and folate derivatives accumulation, SiADCL1 and SiGGH expression levels are key limiting factors in the foxtail millet panicle. Therefore, SiADCL1 and SiGGH expression levels can be targeted in genetic modification studies to improve folate content in foxtail millet seeds in the future. © 2021 Society of Chemical Industry.

Effects of panicle development stage and temperature on rice panicle blast infection by Magnaporthe oryzae and visualization of its infection process

AbstractPanicle blast, caused by the fungus Magnaporthe oryzae (syn. Pyricularia oryzae), directly contributes to yield loss in the field. The effects of panicle development stage and temperature on panicle blast were studied and the infection process of M. oryzae in panicles was visualized. Rice panicles at different development stages from three rice cultivars were inoculated with a conidial suspension in vitro. The rice cultivar Lijiangxintuanheigu was highly susceptible to panicle blast at 5 days postinoculation (dpi) when the pulvinus distance was 15–20 cm. Nanjing 9108 was moderately susceptible to panicle blast when the pulvinus distance was 8–10 cm, but Yliangyou 800 was resistant. The effect of temperature on panicle blast was determined under 22–35 °C temperature treatments. Inoculated panicles placed at temperatures of 28 and 30 °C showed the highest lesion grade based on lesion length at 5 dpi. The infection process of M. oryzae in rice panicles was observed by confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM). M. oryzae initially formed the appressorium to invade through the epidermis of rice panicles at 24 hours postinoculation (hpi). As the disease progressed, the invasive hyphae formed dense mycelial networks in the inner parenchyma cells at 60 hpi. Our results will contribute to the understanding of panicle development stage and temperature effects on panicle blast and improve resistance evaluation methods. Additionally, visualization of the infection process by CLSM and TEM are valuable methods to observe M. oryzae invasive hyphae inside rice panicle cells.

Differential expression of transport and signalling genes in leaves and panicle regulates the development of pollen-free anthers in TGMS red rice

Thermosensitive genic male sterile (TGMS) plants are male sterile above a critical sterility temperature (CST) and become male fertile below CST during a critical thermosensitive stage. It is essential to analyse the gene expression pattern under fertility- and sterility-inducing conditions to understand the mechanisms of male sterility since it is regulated by a single recessive nuclear gene sensitive to environment during a specific stage of panicle development. Hence, this study aims at understanding the molecular mechanism associated with pollen sterility in TGMS system. The newly developed TGMS line on red rice background exhibited male sterility with pollen-free anthers and hence can be recommended as a stable female parent for the development of suitable red rice hybrids to the state of Kerala. Microarray gene expression analysis of TGMS leaf and young panicle revealed that occurrence of pollen-free anthers in the TGMS line during sterility-inducing condition is mainly due to the down-regulation of genes encoding ABC transporter proteins, lipid transfer protein and strictosidine synthase, glucose-methanol-choline oxidoreductase, male sterility protein 2, wax synthase and β-1,3-glucanase. Moreover, pathways involved in the carbohydrate synthesis and transport were also down-regulated during sterility condition. The differential expression of transport and signalling genes regulates the development of pollen-free anthers in TGMS rice.

SiMADS34, an E-class MADS-box transcription factor, regulates inflorescence architecture and grain yield in Setaria italica

A novel MADS-box member SiMADS34 is essential for regulating inflorescence architecture and grain yield in Setaria italica. MADS-box transcription factors participate in regulating various developmental processes in plants. Inflorescence architecture is one of the most important agronomic traits and is closely associated with grain yield in most staple crops. Here, we isolated a panicle development mutant simads34 from a foxtail millet (Setaria italica (L.) P. Beauv.) EMS mutant library. The mutant showed significantly altered inflorescence architecture and decreased grain yield. Investigation of agronomic traits revealed increased panicle width by 16.8%, primary branch length by 10%, and number of primary branches by 30.9%, but reduced panicle length by 25.2%, and grain weight by 25.5% in simads34 compared with wild-type plants. Genetic analysis of a simads34 × SSR41 F2 population indicated that the simads34 phenotype was controlled by a recessive gene. Map-based cloning and bulked-segregant analysis sequencing demonstrated that a single G-to-A transition in the fifth intron of SiMADS34 in the mutant led to an alternative splicing event and caused an early termination codon in this causal gene. SiMADS34 mRNA was expressed in all of the tissues tested, with high expression levels at the heading and panicle development stages. Subcellular localization analysis showed that simads34 predominantly accumulated in the nucleus. Transcriptome sequencing identified 241 differentially expressed genes related to inflorescence development, cell expansion, cell division, meristem growth and peroxide stress in simads34. Notably, an SPL14-MADS34-RCN pathway was validated through both RNA-seq and qPCR tests, indicating the putative molecular mechanisms regulating inflorescence development by SiMADS34. Our study identified a novel MADS-box member in foxtail millet and provided a useful genetic resource for inflorescence architecture and grain yield research.

Effect of Seedling Nitrogen Condition on Subsequent Vegetative Growth Stages and Its Relationship to the Expression of Nitrogen Transporter Genes in Rice.

Nitrogen (N) deficiency is one of the most common problems in soils, limiting crop growth and production. However, the effects of N limitation in seedlings on vegetative growth remain poorly understood. Here, we show that N limitation in rice seedlings restricted vegetative growth but not yield. Aboveground parts were affected mainly during the period of tillering, but belowground parts were sensitive throughout vegetative growth, especially during panicle development. At the tillering stage, N-limited plants had a significantly lower N content in shoots, but not in roots. On the other hand, N content in roots during the panicle development stage was significantly lower in N-limited plants. This distinct response was driven by significant changes in expression of N transporter genes during growth. Under N limitation, N translocation from roots to shoots was greatly sped up by systemic expression of N transporter genes to obtain balanced growth. N limitation during the seedling stage did not reduce any yield components. We conclude that the N condition during the seedling stage affects physiological responses such as N translocation through the expression of N transporter genes.

Rice nitrogen use efficiency does not link to ammonia volatilization in paddy fields

Ammonia (NH3) volatilization is a major pathway of nitrogen (N) losses from paddy fields, and could be potentially mitigated by cultivation of high nitrogen use efficiency (high-NUE) rice cultivars. However, the relationship between NUE and NH3 volatilization has not been validated under field conditions. A field experiment was conducted to evaluate the impact of four rice cultivars with different NUE [Wuyunjing 23 (W23), Zhendao 11 (Z11), Wuyujing 3 (W3), and Aoyusi 386 (A386)] on NH3 volatilization, as well as the related mechanisms. Two high-NUE rice cultivars W23 and Z11 was not more effective in reducing total NH3 volatilization from the paddy field compared to cultivar A386 with the lowest NUE. Cultivar A386 had 12.7–17.8% and 35.7–54.1% lower NH3 volatilization than other three rice cultivars at tillering fertilization stage (TFS) and panicle fertilization stage (PFS), respectively, mainly due to its greater shoot N accumulation, root biomass and volume at TFS and its greater shoot biomass, leaf area index and shoot N accumulation at PFS. There was no significant difference in NH3 volatilization among W23, Z11 and W3 at TFS. However, premature senescence phenomenon at later growth stages of A386 eventually led to its lowest NUE among the four rice cultivars. Our results suggest that NUE of rice does not link to NH3 volatilization from paddy fields. In order to make high-NUE rice cultivars also effective in mitigating NH3 volatilization, future breeding works should aim to improve N uptake capability and canopy structure at early tillering and panicle development stages while prevent premature senescence of rice plants to maintain high yields.

Effect of Soil Moisture Stress at Panicle Development Stage on Growth and Yield of Upland NERICA Cultivars

Effect of Soil Moisture Stress at Panicle Development Stage on Growth and Yield of Upland NERICA Cultivars

Effect of Soil Moisture Stress at Panicle Development Stage on Spikelet Differentiation and Degeneration of Upland NERICA Cultivars

Effect of Soil Moisture Stress at Panicle Development Stage on Spikelet Differentiation and Degeneration of Upland NERICA Cultivars

Transcriptome Profiling Analysis Reveals Co-regulation of Hormone Pathways in Foxtail Millet during Sclerospora graminicola Infection.

Sclerospora graminicola (Sacc.) Schroeter is a biotrophic pathogen of foxtail millet (Setaria italica) and increasingly impacts crop production. We explored the main factors for symptoms such as dwarfing of diseased plants and the “hedgehog panicle” by determining panicle characteristics of varieties infected with S. graminicola and analyzing the endogenous hormone-related genes in leaves of Jingu 21. Results indicated that different varieties infected by S. graminicola exhibited various symptoms. Transcriptome analysis revealed that the ent-copalyl diphosphate synthetase (CPS) encoded by Seita.2G144900 and ent-kaurene synthase (KS) encoded by Seita.2G144400 were up-regulated 4.7-fold and 2.8-fold, respectively. Results showed that the biosynthesis of gibberellin might be increased, but the gibberellin signal transduction pathway might be blocked. The abscisic acid (ABA) 8′-hydroxylase encoded by Seita.6G181300 was continuously up-regulated by 4.2-fold, 2.7-fold, 14.3-fold, and 12.9-fold from TG1 to TG4 stage, respectively. Seita.2G144900 and Seita.2G144400 increased 79-fold and 51-fold, respectively, at the panicle development stage, promoting the formation of a “hedgehog panicle”. Jasmonic acid-related synthesis enzymes LOX2s, AOS, and AOC were up-regulated at the early stage of infection, indicating that jasmonic acid played an essential role in early response to S. graminicola infection. The expression of YUC-related genes of the auxin synthesis was lower than that of the control at TG3 and TG4 stages, but the amidase encoded by Seita.2G313400 was up-regulated by more than 30-fold, indicating that the main biosynthesis pathway of auxin had changed. The results suggest that there was co-regulation of the hormone pathways during the infection of foxtail millet by S. graminicola.

Transcriptome analysis of flowering genes in mango (Mangifera indica L.) in relation to floral malformation

Flowering is a complicated developmental process of physiological and morphological stages under the control of a number of external signals and internal factors. Floral malformation occurring during flower development stage is serious constraint having crippling effect on mango flowering and production leading to heavy economic losses. In mango there is lack of information about the gene expression profile during flower development. We therefore performed transcriptome analysis of Mangifera indica cultivar Amrapalli, by isolating total RNA from different stages of bud development in healthy and malformed tissues. The next generation sequencing were performed using 2 × 150 PE chemistry on the Illumina NextSeq platform resulting in 20.31, 20.77, 20.32, 27.92 and 18.59 million PE reads in MB-1, MB-2, MB-3, HB-1 and HB-2 stages respectively. Higher differential expressions copy numbers of seven flowering genes (MYB30, TPL, bHLH, FTIP1, CDKC2, CPK33, and ATH1) were observed in both the healthybud and panicle development stages as compared to malformed bud development stages. Among the other differentially expressed pattern of flowering genes in six possible combinations, the highly upregulated genes are UBP12, EFS, AGL8, AGL14, AGL20, AGL24, KIN10, MYB30, SUS2, FTIP1, CCT and LDL2 and down regulated genes were like TIL1, TIC, DCL3, GA20OX3, CCT, AP1, AGL6, AGL8, MYB30, AGL8, GCT and GA3OX1. The data set provides information on transcripts putatively associated with embryonic flower, earlier flowering, flowering time control, terminal flower and mads-box protein in healthy and malformed tissues. Out of the observed differentially expressed genes, the transcript profiles of GA20OX3, AGL24 and LDL2, the key genes regulating floral transition and differentiation, were validated through qRT-PCR. Our study provides a resource for exploring the complex molecular mechanisms in flower development and malformations in mango.

Comparative Assessment of UV-B Priming on Vegetative and Reproductive Stages of Oat and Barley

Barley and oat were irradiated with elevated UV-B (+ 3.6 kJ m−2 d−1; 280–315 nm) during the vegetative stage, and their performances were evaluated at the tillering and panicle development stages (PDS). Physiological and biochemical measurements revealed that barley and oat performed almost alike against UV-B at the tillering stage, but the stress imprints led barley to display better performance at the PDS. Chlorophyll content increased under elevated UV-B in both the test crops with a higher increase in barley. Also, efficient synthesis of UV-B-absorbing compounds, i.e. flavonoids and phenolics in barley at the PDS, protected the photosynthetic machinery. Both the crops showed stimulations in growth responses under elevated UV-B except for root length in oat at the PDS. At the PDS, the reduction in total biomass of oat was accompanied with increased biomass allocation to the root portion suggesting the limiting factor for growth was belowground. Results clearly showed that UV-B priming during the vegetative stage enhanced tolerance against stress at the PDS in barley, whereas oat showed recovery for most of the measured parameters except ascorbic acid and biomass. Therefore, improved plant tolerance against UV-B during the panicle growth in barley is meaningful for a higher productivity.

IDENTIFICATION OF RICE CROP PHENOLOGY USING SCATSAT-1 KU-BAND SCATTEROMETER IN PUNJAB AND HARYANA

Abstract. The present study was carried out to analyse rice crop phenology using SCATSAT-1 Scatterometer data. Owing to its higher frequency, Ku-band responds to the dormant elements of surface, corresponding to top of crop canopy. The Ku-band backscatter behaviour is influenced by the structure, moisture content and the roughness of the top canopy which varies with different crop stages. Rice growth undergoes three main phenological stages viz, maximum tillering giving a scattered rough surface (first peak); maximum vegetative stage with a smooth top appearance (first minima after puddling); and the panicle development stage giving more scattering due to the spikelets (second peak). This study aimed at deriving these three stages of rice crop. Rice crop map generated, under FASAL project, using Sentinel-1 SAR data has been utilized and further the sub-pixel area within the SCATSAT-1 pixel. The daily Sigma-0 product was utilised for estimation of dates of major phenological stages of rice crop. A software tool was developed to generate the three phenological stages at 2 km pixel level using the time series backscatter coefficient in VV polarization over rice pixels using polynomial curve fitting. It was observed that peak tillering stage coincides with the first maxima, first minima coincides with the maximum vegetative stage and second maxima coincides with the peak heading or panicle formation stage of the crop. The validation was carried out using ground information from crop cutting experiments and ground truth data. Validation result showed 4 to 12 days difference in maximum vegetative stage.