【Objective】Using low-field nuclear magnetic resonance (NMR) technology, changes in the water phase during the imbibition and stratification of Cercis chinensis seeds were detected nondestructively. Combined with the nutrient content changes during stratification, the role of each water phase was analyzed to reveal the material base and physiological conditions during the germination of C. chinensis seeds. 【Method】After being treated with hot water at 80 ℃, the hardness of C. chinensis seeds was removed and its water absorption curve was calculated by the gravimetric method. Cold stratification was applied to break the physiological dormancy of C. chinensis seeds by random selection. The germination percentage and nutrient content of seeds were determined during different stratification periods. Low-field NMR was employed to investigate the dynamic transitions of the water phase and water content during imbibition and stratification. 【Result】(1)Hot water immersion at 80 ℃ for 5 min followed by 60 days of cold stratification effectively improved the germination rate of C. chinensis seeds. (2)The water absorption curve of C. chinensis seeds exhibited an “S” type variation and from 0 h to 9 h was the rapid water absorption stage. At from 9 h to 24 h, seed water absorption gradually slowed. Ultimately, the seeds entered a balanced water absorption stage after 24 h. (3)NMR spectra revealed that the water mass (x) of C. chinensis seeds and the peak areas of the NMR relaxation spectra (y) exhibited a significant linear relationship, according to the linear regression equation y = 164 604.7 x + 4 962.3, with a correlation coefficient R2 = 0.999 6. (4)NMR T2 relaxation spectra enabled division of the water phases during the imbibition process of C. chinensis seeds into three types: bound water T2a, free water T2b, and newly absorbed water T2c. (5)During the water absorption process from 0 to 3 h, the content of T2a decreased continuously, whereas T2b content increased dramatically. After 3 h, T2c appeared and T2a disappeared. Only T2b and T2c existed in the seeds; both showed an increasing trend, with the peak maximum moving to the right and water mobility being enhanced. Peaks T2b and T2c shifted to the right during stratification, with fluctuating changes in peak area and peak ratio, and in general showed a trend towards increased water mobility. (6)During the stratification process of C. chinensis seeds, the starch content continued to decrease, soluble sugar content increased, and soluble protein content showed an increasing trend, followed by a decreasing trend. 【Conclusion】Water mobility is enhanced during the absorption and the stratification of C. chinensis seeds. There are three types of water phases in the imbibition process of C. chinensis seeds: T2a, T2b and T2c. However, only T2b and T2c appear during stratification. The changes in the nutrient contents of starch, soluble sugars, and soluble proteins roughly follow the same trend as those in T2b content. The fluctuations in water in each phase provides a suitable water environment for C. chinensis seed germination, and the changes in T2b during the stratification process might be closely related to germination.
【Objective】The study explored the effects of brassinolide (BR) on enzyme activities related to fatty acid synthesis and oil accumulation in seeds of Styrax tonkinensis. The aim was to provide theoretical and practical data for studies of the mechanism by which exogenous BR promotes fatty acid synthesis and oil accumulation in seeds of S. tonkinensis. 【Method】Ten-year-old seed trees of S. tonkinensis were sprayed with four different concentrations of brassinolide solution: 1(BR 1), 5(BR 5), 10(BR 10) and 20(BR 20) μmol/L, with distilled water sprayed as the control. The different BR concentrations were sprayed 45, 65, 95 and 125 d after flowering. Fruit samples were collected 50, 70, 100 and 130 d after flowering. The activities of fatty acid synthase (FAS), 1-aminocyclopropane-1-carboxylate (ACC) and diacylglycerol acyltransferase (DGAT) were measured during seed development. Fruit fresh weight and seed crude fat mass fraction were also determined. The effects of different concentrations of BR on enzyme activities related to fatty acid synthesis in S. tonkinensis seeds were analyzed. 【Result】BR treatment had significant effects on the activities of enzymes related to fatty acid synthesis during the seed development of S. tonkinensis. FAS activity was low at 50 d after flowering, increased, significantly and peaked at 100 d after flowering, and then decreased slowly. At 100 d after flowering, the activity of FAS in the BR5 and BR10 treatments reached the maximum value at the same time. The respective values of 329.104 and 326.744 nmol/(min·mg) exceeded the control value by 1.8 times. The ACC activity of S. tonkinensis seeds increased, then decreased, then increased again. At 70 d after flowering, the ACC activity in the BR5 treatment peaked 20.50 nmol/mg, which was 5.9 times that of the control group. The activity of DGAT in the different treatments first increased and then decreased, reaching a peak at 100 d after flowering. The activity of DGAT in each BR treatment group was significantly higher than that in the control group. DGAT activity in the BR5 treatment was highest at 6.03 nmol/mg, which was 1.2 times of that the control group. BR promoted the activities of FAS, ACC and DGAT in S. tonkinensis seeds, with the most significant effect with the BR5 treatment. During the four periods of time, the medium concentration of BR treatment improved the crude fat fraction of S. tonkinensis seeds. Seventy days after flowering, there were significant differences in the seed crude fat mass fraction under different treatments, and that of the BR5 treatment was significantly higher than that of the other treatments. The fresh weight of S. tonkinensis fruits increased after treatment with different concentrations of BR. The BR5 treatment had the greatest effect on fruit fresh weight, except at 100 d after flowering. There was a significant positive correlation between enzyme activities related to fatty acid synthesis and both seed crude fat mass fraction and fruit fresh weight. 【Conclusion】 The dynamic changes in FAS, ACC and DGAT activities showed that BR treatment increased the activities of enzymes related to fatty acid synthesis and promoted fatty acid synthesis during seed development. The BR5 treatment had the best effect. BR treatment also increased fruit fresh weight and seed crude fat fraction. Correlation analysis showed that the activities of enzymes related to fatty acid synthesis in the seeds of S. tonkinensis were positively correlated with fruit fresh weight and seed crude fat mass fraction.
【Objective】The study explored the changes of water content, storage substance content, and enzyme activity during the germination process of Pinus bungeana seeds, in order to reveal the physiological mechanism of temperature that affects the seed germination. 【Method】Seed germination was performed at various temperatures to study the effects of temperature on the extent of germination. Physiological indicators, such as the content of water, soluble sugar, starch, soluble protein, crude fat and the activities of amylase, protease and acid phosphatase were measured during the germination process. 【Result】A high germination percentage (approximately 90%) was obtained when the seeds were cultured at 15 and 20 ℃. As the culture temperature continued to rise to 25 and 30 ℃, the radicle protrusion and seed germination were seriously hindered, resulting in a sharp drop in germination percentage to <10%. At 20 ℃, the change of water content during germination could be characterized into three stages: rapid increase, period of retardation, and another rapid increase. During germination, the catabolism and anabolism of substances occurred vigorously in the seeds. The soluble sugar content initially decreased and then gradually increased. As starch began to hydrolyze with a decreased content after six days of cultivation, the crude fat and soluble protein were degraded into small molecules as catalyzed by the corresponding enzymes for embryo utilization after 10 days of cultivation. At 25 ℃, the water absorption process of seeds stayed in the retardation period throughout. At this incubation temperature, the activities of acid phosphatase, amylase, and protease in seeds was inhibited due to the excessive temperature, thus affecting the degradation of crude fat, soluble protein and soluble starch. In addition, the soluble sugar content was slightly decreased to keep the ‘still’ state of the seeds with low consumption. 【Conclusion】The suitable temperature range for seed germination of P. bungeana was 15-20 ℃. However, if the temperature continued to rise, seed germination was hindered and thermal inhibition occurred. At the favorable temperature of 20 ℃, seeds would preferentially use the nutrients stored in the embryo when germination occurred. Carbohydrates are first decomposed and utilized, followed by the mobilization of proteins and lipids. Degradation of a large amount of fat began after the radicle broke through the seed coat. At a high temperature of 25 ℃, the activity of enzymes in the seeds was inhibited, resulting in the catabolism of macromolecular substances was hindered. Ultimately, the embryo could not absorb and utilize enough nutrients to complete the germination process.
【Objective】 Circular RNAs (circRNAs) are a class of endogenous non-coding RNA produced by reverse alternative splicing of transcripts, which play crucial roles in plant growth and development. This study aimed to identify circRNAs in germinated seeds of moso bamboo (Phyllostachys edulis), and investigate their expression under drought and salt stress conditions, providing a foundation for exploring the molecular regulation mechanism of bamboo seed germination under abiotic stress resistance. 【Method】 polyethylene glycol (PEG) 6000 and NaCl were used to simulate drought and salt stress, respectively. The strand specific libraries were constructed for moso bamboo seeds samples at the seed coat rupture stage under treatments of H2O, 10% (mass fraction) PEG, 15% PEG, 50 and 100 mol/L NaCl. High throughout sequencing and biological information analysis were used to identify and analysis the expressional pattern of circRNAs. 【Result】 A total of 1 446 circRNAs were identified in all samples, with 76.34% of circRNAs originating from exon region; The circRNAs with the highest expression levels in bamboo germinating seeds under different treatments were identified as plant_ circ_ 0001703, plant_ circ_ 0001728, plant_ circ_ 0000358, plant_ circ_ 0001236 and plant_ circ_ 0001728;Compared with control, 524, 505, 467 and 474 circRNAs were significantly differentially expressed in germinating seeds under the four stress treatments. The original genes of differentially expressed circRNAs were significantly enriched in various GO and KEGG pathways. 【Conclusion】 A total of 1 446 circRNAs were found to be expressed in moso bamboo germinating seeds, with 1 056 circRNAs responding to drought or salinity stresses during seed germination. Genes involved in acylhydrolase enzyme activity and sphingolipid metabolism pathways may play a crucial role in regulating bamboo seed germination under PEG or NaCl stress conditions.
【Objective】This manuscript described the realized genetic gain and construction techniques of an open-pollinated seedling and seed orchard of Masson pine (Pinus massoniana). 【Method】The orchard was established in the 1990 to 1992 period and covers an area of 33.33 hm2 in Baisha State-Owned Forest Farm, Shanghang County, Fujian Province, China. The orchard comprises more than 198 families of trees that were intensively selected from the excellent provenance area of Fujian Province. The orchard design was classified into two types: (1) Combined design of seed production area with progeny test area. (2) Separated design of seed production area and progeny test area. Based on the results of open-pollinated forests progeny test, trees with the lower breeding values were removed from the seed orchard (genetic thinning) on three occasions in 2000, 2004 and 2008, respectively. In 2003, a progeny test forest with seedlings from 68 half-sib families of the seedling seed orchard including a commercial check was established.【Result】A realistic genetic gain of 8.5% was obtained based on a test of 6-year offspring of Masson pine open-pollinated seedling seed orchard, and the volume growth of improved seed plantation was increased by 30% more than that of the unimproved stand. The results of simple sequence repeat (SSR) molecular analysis showed that the seedling seed orchards had high genetic diversity and random mating degree. The establishment of the first generation free-pollinated seed garden of Masson pine was successful. The following are the two key findings: (1) Quality and quantity of superior tree selection is the basis for achieving high genetic gain and continuing genetic improvement. (2) Scientific genetic evaluation of the progeny population and genetic thinning in the production population are the key techniques. (3) The detection, regulation and daily management of the mating system in a seed orchard are important conditions to ensure the normal operation of the orchand. 【Conclusion】 (1) For some fast-growing tree species such as eucalyptus and Masson pine, the seed orchard crops are not appropriate for pruning and dwarfing culture. It is more advantageous to adopt the technique of “Integrating the measured population and the producing population” to build the orchard. (2) Information regarding juvenile-adult correlation of the main traits of the established tree species is not yet available. It is necessary to carry out pruning and dwarfing culture. It is valuable to use the separated design of seed production area and progeny test area and to use the genetic evaluation data obtained from the separated progeny test to guide the genetic thinning of production population in the seed orchard production. In a word, the multi-generation seed orchard should be established in a location with good isolation conditions and relatively gentle terrain, and the orchard crops should be maintained without pruning and dwarfing to retain the natural tree shape. After completion of the production task in the seed orchards, the seed orchard trees could be transformed into forest tourism forest, forest health forest or timber reserve forest, to give full play to the multiple functions of the forest and reduce the operating cost of the forest improved seed base. This is a new model of multi-generation low-cost construction of seed orchards worth exploring.
