Spermidine enhances heat tolerance of rice seeds during mid-filling stage and promote subsequent seed germination.

Introduction: Heat stress is a vital factor which restricts rice seed quality and yield. However, the response mechanism to heat stress in the mid filling stage of rice seed is unclear. Methods: In the present study we integrated phenotypic analysis with biochemical, hormone, and gene expression analysis in order to explore technologies for improving rice seeds heat tolerance and subsequent seed germination. Results: Spermidine (Spd) application effectively alleviated the damage of heat stress treatment during mid-filling stage (HTM, 12-20 days after pollination) on seed development, promoted subsequent seed germination and seedlings establishment. Spd significantly increased seed dry weight, starch and amylose contents during seed development under heat stress, and improved seed germinate, seedlings establishment and seedling characteristics during germination time. Biochemical analysis indicated that, HTM significantly decreased the activities of several starch synthase enzymes and led to a decrease in starch content. While Spd treatment significantly enhanced the activities of ADP-glucose pyrophosphorylas and granule-bound starch synthase, as well as the corresponding-genes expressions in HTM rice seeds, resulting in the increases of amylose and total starch contents. In addition, Spd significantly increased the catalase and glutathione reductase activities together with corresponding-genes expressions, and lowered the overaccumulation of H2O2 and malondialdehyde in HTM seeds. In the subsequent seed germination process, HTM+Spd seeds exhibited dramatically up-regulated levels of soluble sugars, glucose, ATP and energy charges. Consistently, HTM+Spd seeds showed significantly increased of α-amylose and α-glucosidase activities as well as corresponding-genes expressions during early germination. Moreover, HTM evidently increased the abscisic acid (ABA) content, decreased the gibberellin (GA) content, and accordingly significantly declined the GA/ABA ratio during early rice seeds germination. However, Spd treatment did not significantly affect the metabolism of GA and ABA in seed germination stage. Discussion: The present study suggested that Spd treatment could effectively alleviate the negative impact of HTM on seed development and the subsequent seed germination, which might be closely correlated with starch synthesis and antioxidant defense during seed filling period, starch decomposition and energy supply in seed germination period.

The Effects of Genotype × Environment on Physicochemical and Sensory Properties and Differences of Volatile Organic Compounds of Three Rice Types (Oryza sativa L.).

Understanding the effects of genotype, environment and their interactions on rice quality is of great importance for rice breeding and cultivation. In this study, six rice varieties with two indica, two japonica and two indica-japonica types of rice were selected and planted at ten locations in Zhejiang Province to investigate the genotype (G) × environment (E) on physicochemical and sensory properties and the differences of volatile organic compounds (VOCs) among the three types of rice. Analysis of variances showed that apparent amylose content (AC), total protein content (PC), alkali spreading value (ASV), RVA profiles, and appearance (ACR), palatability (PCR), and sensory evaluation value (SEV) of cooked rice and texture of cooled cooked rice (TCCR) were mainly affected by genotypic variation, whereas the smell of cooked rice (SCR) was mainly affected by environment (p < 0.05). The G × E effect was significant for most parameters. The weather in the middle and late periods of filling had important effects on the formation of rice quality, especially on setback (SB) and pasting temperature (PT) (p < 0.01). They were negatively correlated with the texture of cooked rice (TCR) and SEV (p < 0.05). Peak viscosity (PV) and breakdown (BD) were positively related to the sensory evaluation parameters (p < 0.01) and could be used to predict cooked rice quality. A total of 59 VOCs were detected, and indica, japonica and indica-japonica had 9, 6 and 19 characteristic compounds, respectively. The principal component analysis showed that the physicochemical and sensory properties and VOCs of indica-japonica rice were more stable than those of indica and japonica rice at ten locations in Zhejiang Province. It is helpful for rice breeders to understand how the environment affects the physicochemical, sensory properties and VOCs of the three rice types, and it is also important for food enterprises to provide rice products with stable quality.

Effect of storage time on chemical compositions, physiological and cooking quality characteristics of different rice types.

BACKGROUND: Storage affects rice quality significantly. The aim of this study was to investigate the changes in the chemical composition and in the physiological and cooking quality characteristics of three rice types after 1 year storage at 25 °C. RESULTS: Two japonica, two indica, and two indica-japonica hybrid rice varieties were selected. After storage, the total starch content decreased. The amylose content of japonica, indica, and indica-japonica hybrid rice increased by 9.63%-11.65%, 2.99%-4.67%, and 8.07%-8.97%, respectively, and the fat content decreased by 60.00%-65.00%, 37.21%-46.51%, and 41.67%-42.42%, respectively. The abscisic acid (ABA) and raffinose content decreased after 1 year's storage; the former decreased gradually during the storage and the latter increased by 19.35%-45.45%, 7.02%-10.77%, and 16.13%-28.13%, respectively, after 4 months' storage and then decreased to the lowest level after 1 year's storage. The activity of antioxidant enzymes deceased, which resulted in the increases in fatty acid value and malondialdehyde (MDA). The changes in chemical composition after 1 year storage led to the deterioration of rice cooking quality, which was reflected in the decrease in viscosity and increases in gelatinization temperature and cooked rice hardness. CONCLUSION: After 1 year's storage, the rice chemical composition changed and physiological and cooking quality characteristics decreased. Compared with japonica and indica-japonica hybrid rice, indica rice was more stable during 1 year storage. This may be due to the higher content of ABA and raffinose in fresh rice. Our findings will provide information for the identification and breeding of storable rice cultivars. © 2022 Society of Chemical Industry.

Oligomeric Proanthocyanidins Confer Cold Tolerance in Rice through Maintaining Energy Homeostasis.

Oligomeric proanthocyanidins (OPCs) are abundant polyphenols found in foods and botanicals that benefit human health, but our understanding of the functions of OPCs in rice plants is limited, particularly under cold stress. Two rice genotypes, named Zhongzao39 (ZZ39) and its recombinant inbred line RIL82, were subjected to cold stress. More damage was caused to RIL82 by cold stress than to ZZ39 plants. Transcriptome analysis suggested that OPCs were involved in regulating cold tolerance in the two genotypes. A greater increase in OPCs content was detected in ZZ39 than in RIL82 plants under cold stress compared to their respective controls. Exogenous OPCs alleviated cold damage of rice plants by increasing antioxidant capacity. ATPase activity was higher and poly (ADP-ribose) polymerase (PARP) activity was lower under cold stress in ZZ39 than in RIL82 plants. Importantly, improvements in cold tolerance were observed in plants treated with the OPCs and 3-aminobenzamide (PARP inhibitor, 3ab) combination compared to the seedling plants treated with H2O, OPCs, or 3ab alone. Therefore, OPCs increased ATPase activity and inhibited PARP activity to provide sufficient energy for rice seedling plants to develop antioxidant capacity against cold stress.

Yield-Related QTL Clusters and the Potential Candidate Genes in Two Wheat DH Populations.

In the present study, four large-scale field trials using two doubled haploid wheat populations were conducted in different environments for two years. Grain protein content (GPC) and 21 other yield-related traits were investigated. A total of 227 QTL were mapped on 18 chromosomes, which formed 35 QTL clusters. The potential candidate genes underlying the QTL clusters were suggested. Furthermore, adding to the significant correlations between yield and its related traits, correlation variations were clearly shown within the QTL clusters. The QTL clusters with consistently positive correlations were suggested to be directly utilized in wheat breeding, including 1B.2, 2A.2, 2B (4.9-16.5 Mb), 2B.3, 3B (68.9-214.5 Mb), 4A.2, 4B.2, 4D, 5A.1, 5A.2, 5B.1, and 5D. The QTL clusters with negative alignments between traits may also have potential value for yield or GPC improvement in specific environments, including 1A.1, 2B.1, 1B.3, 5A.3, 5B.2 (612.1-613.6 Mb), 7A.1, 7A.2, 7B.1, and 7B.2. One GPC QTL (5B.2: 671.3-672.9 Mb) contributed by cultivar Spitfire was positively associated with nitrogen use efficiency or grain protein yield and is highly recommended for breeding use. Another GPC QTL without negatively pleiotropic effects on 2A (50.0-56.3 Mb), 2D, 4D, and 6B is suggested for quality wheat breeding.

Alleviation of lead toxicity by 5-aminolevulinic acid is related to elevated growth, photosynthesis, and suppressed ultrastructural damages in oilseed rape.

Lead (Pb) is a widely spread pollutant and leads to diverse morphological and structural changes in the plants. In this study, alleviating role of 5-aminolevulinic acid (ALA) in oilseed rape (Brassica napus L.) was investigated with or without foliar application of ALA (25 mg L(-1)) in hydroponic environment under different Pb levels (0, 100, and 400 µM). Outcomes stated that plant morphology and photosynthetic attributes were reduced under the application of Pb alone. However, ALA application significantly increased the plant growth and photosynthetic parameters under Pb toxicity. Moreover, ALA also lowered the Pb concentration in shoots and roots under Pb toxicity. The microscopic studies depicted that exogenously applied ALA ameliorated the Pb stress and significantly improved the cell ultrastructures. After application of ALA under Pb stress, mesophyll cell had well-developed nucleus and chloroplast having a number of starch granules. Moreover, micrographs illustrated that root tip cell contained well-developed nucleus, a number of mitochondria, and golgi bodies. These results proposed that under 15-day Pb-induced stress, ALA improved the plant growth, chlorophyll content, photosynthetic parameters, and ultrastructural modifications in leaf mesophyll and root tip cells of the B. napus plants.

Adsorption of methylene blue onto activated carbon produced from tea (Camellia sinensis L.) seed shells: kinetics, equilibrium, and thermodynamics studies.

Tea (Camellia sinensis L.) seed shells, the main byproduct of the manufacture of tea seed oil, were used as precursors for the preparation of tea activated carbon (TAC) in the present study. A high yield (44.1%) of TAC was obtained from tea seed shells via a one-step chemical method using ZnCl2 as an agent. The Brunauer-Emmett-Teller (BET) surface area and the total pore volumes of the obtained TAC were found to be 1530.67 mg(2)/g and 0.7826 cm(3)/g, respectively. The equilibrium adsorption results were complied with Langmuir isotherm model and its maximum monolayer adsorption capacity was 324.7 mg/g for methylene blue. Adsorption kinetics studies indicated that the pseudo-second-order model yielded the best fit for the kinetic data. An intraparticle diffusion model suggested that the intraparticle diffusion was not the only rate-controlling step. Thermodynamics studies revealed the spontaneous and exothermic nature of the sorption process. These results indicate that tea seed shells could be utilized as a renewable resource to develop activated carbon which is a potential adsorbent for methylene blue.