Content of Frontier & focus: seed dormancy and germination in our journal

Published in last 1 year |  In last 2 years |  In last 3 years |  All Please wait a minute... For Selected: Download Citations EndNote Reference Manager ProCite BibTeX RefWorks Toggle Thumbnails Select Water Absorption Characteristics of Albizzia julibrissin Seeds by Nuclear Magnetic Resonance Technique Tiantian Du,Song Dai,Teng Qian,Mingwei Zhu,Li Chen,Zhonghui Zhang,Shuxian Li Scientia Silvae Sinicae    2022, 58 (4): 22-31.   DOI: 10.11707/j.1001-7488.20220403 Abstract （234）   HTML （10）    PDF （2486KB）（154）       Knowledge map    Save Objective: Imbibition is the initial and most important stage of seed germination. Nuclear magnetic resonance (NMR) technology was used to explore the initial water absorption site and the spatial and temporal movement of water throughout the seed after hot water treatment from the perspective of time and space, revealing the changes of water phase in seeds. Thisprovides a new method for the study of water absorption in seeds. Method: The seeds of A. julibrissin were treated with hot water at an initial temperature of 80 ℃. The water absorption was calculated by the increase in weight after soaking divided by the initial weight. MRI technology was used to observe the initial water absorption location and the movement of water in the seeds after water absorption, combined with T2 relaxation detection technology to explore the dynamic changes in phase and state of the water. Result: 1) The water absorption curve of A. julibrissin seeds exhibited an "S" type behavior, where the water absorption of seeds increased slowly in the early stage (0-4 h); the seeds entered the rapid water absorption stage during 4-12 h, where the water absorption increased greatly; finally the seeds entered the slow water absorption stage at 12 h. During the process of water absorption, the MRI result of the seeds showed that the water initially entered the seeds from the micropyle, then migrated inside the seed through three paths, namely: ①The water moved along the vascular bundle at the seed coat toward the chalazal; ② The water moved down towards the chalazal through the gap between the seed coat and cotyledons, entering the lateral side of cotyledons; ③ The water entered the hypocotyl through the radicle, then entered the cotyledons and moved to the chalazal, but its moving speed was noticeably slower than that of the second path. At the initial stage of water absorption (0-6 h), the imbibition area of the right seed coat was significantly larger than that of the left. Later, with the extension of soaking time, the imbibition speed of the left seed coat was faster, and there was no significant difference between the imbibition area of the left seed coat and that of the right seed coat. 2) The NMR spectrum showed that the water content (X) of A. julibrissin and the peak area (S) had a linear relationship, and the linear regression equation was: S=21 132X+695.05, R2=0.999 6. 3) There were three main states of water in A. julibrissin seeds, namely bound water, cytoplasmic bulk water, and extra-cellular free water. 4) At 0 h, bound water accounted for 45.13% of the water in the cell, extracellular free water accounted for 53.51%, and cytoplasmic bulk water was almost absent. During the process of water absorption, the content of bound water decreased significantly, which continued to decrease, accounting for only 2.08% by 48 h; the content of cytoplasmic bulk water increased rapidly at first and then decreased gradually. The content of extra-cellular free water increased continuously. At 48 h, the percentages of cytoplasmic bulk water and extra-cellular free water were 29.12% and 68.80%, respectively. During the whole process of water absorption, the percentages of water phases in three states was always in dynamic change, and the content of extracellular free water was much higher than that in other states. During this water absorption process, the peak of extra-cellular free water and bound water shifted to the left. Conclusion: The micropyle is the initial sites of water absorption in the seeds of A. julibrissin seeds. The water moves through the seed via the seed coat on both sides, the gap between the seed coat and the cotyledon, and the hypocotyl, and moves towards the chalazal. During the process of water absorption, there are three different water phases, namely bound water, cytoplasmic bulk water, and extra-cellular free water in the seeds of A. julibrissin, and they transform into each other during the entire imbibition process, which prepares the seed for germination. Table and Figures | Reference | Related Articles | Metrics Select Characteristics of Taxodinm distichum var. imbricatum Seed Coat and Their Effects on Seed Dormancy Zhihua Yang,Xuemei Chen,Chunhua Chen,Limiao Zhang,Zhi Dong,Xue Tan,Changxiao Li Scientia Silvae Sinicae    2022, 58 (4): 11-21.   DOI: 10.11707/j.1001-7488.20220402 Abstract （310）   HTML （7）    PDF （3672KB）（140）       Knowledge map    Save Objective: The seed germination of pond cypress is slow, uneven andthus leading to a low seedling rate, which brings certain difficulties to production management. The present study is to identify the causes of seed dormancy of pond cypress by studying the relationship between seed coat and seed dormancy, so as to provide a theoretical basis for the practical application of pond cypress seed and a technical guidance for ecological restoration in the Three Gorges Reservoir area. Method: The relationship between seed coat and seed dormancy of pond cypress was studied through observing the structure of seed and seed coat, germination test, TTC activity test, water permeability test, extraction and bioassay of endogenous inhibitors in different parts of seeds, as well as extraction, separation and bioassay of inhibitors contained in seed coat. Result: 1) The seed coat of pond cypress from outer to inner in order is: epicuticle, sarcotesta, sclerotesta, and endotesta. Compared with the control, the hot water treatment could promote the abscission of epicuticle, but had no obvious effect on the structure of seed coat, and the seed coat permeability had no obvious change. After 15 minutes of acid treatment, corrosion cracks and pits appeared on the seed surface, the structure of seed coat was damaged, the seed coat became thinner and the seed coat permeability increased; After 30 minutes of acid treatment, a large number of corrosion cracks and pits appeared on the surface of seed coat, which further damaged the seed coat structure while enhancing the seed permeability. 2) The viability of newly harvested pond cypress seeds was at 80.95%, but the seeds did not germinate and had significant dormancy. 3) The seed coat of pond cypress has a certain degree of water permeability, and the kernel can absorb part of the water. Although the acid treatment is conducive to promoting the seed kernel to absorb water, the hard seed coat hinders the water absorption and expansion of the kernel to a certain extent, which makes the kernel absorb water slowly, and may produce mechanical resistance to the elongation and growth of the radicle. 4) The seeds of pond cypress contain endogenous inhibitors. The inhibition intensity of methanol extracts from different parts on seedling and root growth was as follows: seed coat > kernel. The result showed that the inhibitive substances mainly existed in the seed coat instead of seed kernel. 5) The methanol extract from seed coat of pond cypress was separated and bioassayed by systematic separation method. The result showed that the methanol extracts from seed coat inhibited the growth of Brassica chinensis seedlings at different degrees. When the concentration of each separation phase was 1 g ·mL-1, the inhibition intensity of Brassica chinensis seedling height was petroleum ether phase > ethyl acetate phase > ether phase > methanol phase > aqueous phase, and the inhibition intensity of Brassica chinensis root length was petroleum ether phase > methanol phase > water phase > ethyl acetate phase > ether phase. Petroleum ether phase and methanol phase are the main phases with inhibitory effect. Conclusion: The water permeability of seed coat of pond cypress may not be the main factor causing seed dormancy, but the mechanical restraint of seed coat may lead to slow seed germination. The inhibitory substances in seed coat of pond cypress are mainly concentrated in petroleum ether phase, whose components are characterized with smaller polarity molecules. Therefore, the structure of seed coat and endogenous inhibitors are the main causes of seed dormancy. The seed of pond cypress may take on a comprehensive dormancy (combinational dormancy, PY+PD) with both physical and physiological dormancy traits. Table and Figures | Reference | Related Articles | Metrics Select Seed Germination and Emergence Characteristics and Physiological and Biochemical Changes of Quercus variabilis Na Wang,Jiaxi Wang,Guolei Li,Qing Li,Lin Zhu,Tian Li,Wen Liu Scientia Silvae Sinicae    2022, 58 (4): 1-10.   DOI: 10.11707/j.1001-7488.20220401 Abstract （413）   HTML （22）    PDF （1832KB）（271）       Knowledge map    Save Objective: Under natural conditions, Quercus variabilis seeds have uneven emergence. This study monitored the characteristics of seed germination and emergence of Q. variabilis day by day, explored the characteristics of seed germination and emergence of Q. variabilis and its own physiological and biochemical change process, analyzed the mechanism of irregular emergence, and provided theoretical support for accurate regulation of seedling quality. Method: Through the dynamic observation of the germination and emergence process of Q. variabilis seeds, according to the characteristics of seed morphological changes and emergence statistics during the germination and emergence process of Q. variabilis seeds, the germination and emergence process of Q. variabilis seeds was divided into stages and periods, and the physiological and biochemical changes of Q. variabilis seeds germinated and emerged at different stages and periods were measured, The activities of peroxidase (POD) and superoxide dismutase (SOD) were determined by plant physiological method, the contents of gibberellin (GA3), indoleacetic acid (IAA) and abscisic acid (ABA) were determined by high performance liquid chromatography, and the contents of soluble sugar and starch were determined by anthrone colorimetry, α- amylase and β- amylase was determined by 3, 5-dinitrosalicylic acid colorimetry. Result: 1) Q. variabilis seeds began to germinate on the 6th day after sowing, and ended on the 33rd day. The germination cycle was 27 days, and the cumulative germination rate was 73.6%, of which the median germination was 14 days. Q. variabilis seeds began to emerge on the 21st day after sowing and ended on the 60th day. The emergence cycle was 40 days, and the cumulative emergence rate was 66.6%, of which the median emergence was 29 days. The emergence process of Q. variabilis seeds can be divided into three periods. When the average daily emergence rate of Q. variabilis seeds exceeds 3%, it is the emergence peak (25-30 days after sowing), which accounts for 10% of the whole emergence cycle. During this period, the number of seedlings accounts for 44% of the total number of seedlings; Before this period, the emergence stage is the rising stage (1-24 days after sowing), accounting for 40% of the whole emergence cycle, and the number of emerging seeds accounts for 11% of the total number of seedlings; The peak period is followed by the emergence decline period (31-60 days after sowing), accounting for 50% of the whole emergence cycle, and the number of emergence seeds accounts for 45% of the total number of emergence. 2) In the process of Q. variabilis seed germination, the POD activity in the first germinated Q. variabilis seed is higher. In the process of Q. variabilis seed emergence, the pod and SOD activities in the seed are higher when the number of seeds is large. 3) Compared with germinating seeds, GA3 increased by 64%, ABA decreased by 30.3%, soluble sugar content decreased by 51% and starch content decreased by 24.1%, α-amylase activity decreased by 45%, while β- amylase activity increased by 67.7%. Conclusion: The germination and emergence of Q. variabilis seeds are two independent processes, and some seeds have germinated but not emerged in the end. The long period from seed germination to seedling emergence and large individual differences are the main factors leading to uneven seedling emergence of Q. variabilis while seed dormancy of Q. variabilis is different among individuals, and the seed germination cycle is long, which is also one of the reasons for the uneven emergence of Q. variabilis seeds; POD and SOD mainly affected the germination stage of Q. variabilis seeds; GA3 and IAA promoted the emergence of Q. variabilis seeds. The higher the content, the faster the emergence rate; ABA inhibited the emergence of Q. variabilis seeds. Table and Figures | Reference | Related Articles | Metrics