| 珍稀濒危植物蒜头果种子萌发特征与幼苗类型的研究 |
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| 引用本文：普 甜，栗宏林，王 娟，潘 悦，张平芳，陈婉东.珍稀濒危植物蒜头果种子萌发特征与幼苗类型的研究[J].西北植物学报,2023,43(2):242~254 |
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| 基金项目:国家自然科学基金(32160008)；云南省重大基础专项-生物资源数字化开发应用(202002AA100007)；云南省万人计划“云岭产业技术领军人才”专项(云发改［2018］ 212号)；云南省千人计划“高端外国专家”专项 |
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| 中文摘要:以去除果皮后阴干的珍稀濒危植物蒜头果种子为材料，在温室大棚沙池内进行层积处理，从层积处理开始至子叶出土的不同萌发阶段，考察蒜头果种子发育形态、贮藏物质积累、酶活性以及幼苗类型等变化特征，初步探讨其种子休眠形成原因。结果显示：(1)蒜头果种子从解除休眠开始至萌发形成幼苗的过程约需195 d，其中幼胚的形态发育后熟约需75 d，随后30 d内是种子集中萌发的时期，其发芽率达到最高(53.33%)；依据种胚发育形态的标志特征将此过程划分为7个阶段(S1~S7阶段)：S1阶段种子未萌发，S2阶段种胚“露白”，S3阶段胚根突破种皮长超过1 cm，S4阶段下胚轴与胚根连接处形成弯钩结构，S5阶段“S”型胚形成及胚根前端膨大，S6阶段种子不仅具有膨大的胚根且已有侧根的分化，S7阶段子叶脱落，胚芽出土，真叶出现。(2)蒜头果种子在湿沙层积过程中，种胚胚长和胚率从S1阶段的(5.49±1.57)mm和(19.48±5.72)%分别增加至S6阶段的(67.92±2.94)mm和(240.75±15.29)%，胚率平均增加了12.4倍，显示蒜头果种子的胚需要经历后熟过程才能萌发，属于胚后熟型种子。(3)从种子生理指标看，随着湿沙层积时间的增加，种胚内可溶性蛋白含量、淀粉含量先降后升，可溶性糖和丙二醛(MDA)含量以及超氧化物歧化酶(SOD)及过氧化物酶(POD)活性总体呈先升后降的趋势，而同期胚乳的大小和形态没有明显变化，但其淀粉、可溶性糖、可溶性蛋白等含量以及SOD和POD活性总体呈下降的趋势。(4)种子胚率、萌发率与胚乳内可溶性蛋白含量、淀粉含量均呈极显著负相关关系(P＜ 0.01)，与可溶性糖含量呈极显著正相关关系。研究发现，蒜头果种子从解除休眠至萌发前内部发生了一系列的生理生化变化，包括胚乳中贮藏营养物质可溶性蛋白等大分子物质的降解和酶活性不断下降，为种胚完成后熟解除休眠进入萌发提供了物质和能量；生理指标的变化过程与种胚的形态发育过程相互配合共同完成蒜头果种子的萌发；蒜头果种子完成萌发形成原始的、紫玉盘型的、子叶留土的幼苗类型，子叶仅具有吸收营养成分的功能，而不具有同化功能。 |
| 中文关键词:蒜头果 种子萌发 种子后熟 种胚形态 生理变化 幼苗类型 |
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| Seed Germination Characteristics and Seedling Types of Malania oleifera, a Rare and Endangered Plant |
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| Abstract:Rare and endangered M.oleifera seeds dried in shade after peel removal are used as materials, stratification treatment in greenhouse sand pond, different germination stages from stratification treatment to cotyledon excavation, we investigated the change characteristics of seed development morphology, storage material accumulation, enzyme activity and seedling type of M.oleifera, to understand the causes of seed dormancy. The results showed that: (1) it takes about 195 days for M. oleifera seed to germinate and form seedlings from the beginning of dormancy release. It takes about 75 days for the morphological development of young embryo to ripen, and then 30 days later is the period when the seeds germinate intensively, with the highest germination rate. This process can be divided into 7 stages (S1-S7 stages) according to the characteristics of the developmental morphology of the embryo: The seeds do not germinate at S1 stage; S2 stage seed embryo “exposed”; At S3 stage, the radicle breaks through the seed coat more than 1 cm long; At S4 stage, the junction between hypocotyl and radicle forms a hooked structure; The formation of “S” type embryo and the enlargement of the front end of radicle at S5 stage; At S6 stage, the seeds not only have enlarged radicles, but also have lateral roots; At S7 stage, cotyledons fall off, germ unearthed and true leaves appear. (2) M.oleifera seeds in the process of wet sand stratification, seed embryos length and embryo rate increased from (5.49±1.57) mm and (19.48±5.72)% during stratification at S1 stage to (67.92±2.94) mm and (240.75±15.29)% at S6 stage, the embryo rate increased by 12.4 times on average. It shows that the embryo of M. oleifera seeds needs to go through the post-ripening process to germinate, which belongs to the post-embryonic type seeds. (3) From the perspective of seed physiological indicators, with the increase of wet sand stratification time, soluble protein content and starch content in seed embryo decreased first and then increased, while the contents of soluble sugar and malondialdehyde (MDA), and the activities of superoxide dismutase (SOD) and peroxidase (POD) increased first and then decreased; However, the size and shape of endosperm did not change significantly at the same time, the contents of starch, soluble sugar, soluble protein, and the activities of SOD and POD showed a general downward trend. (4) The percentage of embryo and germination of seeds were negatively correlated with the contents of soluble protein and starch in endosperm, there was a very significant positive correlation with soluble sugar content (P<0.01). The study found that, M. oleifera seed undergoes a series of physiological and biochemical changes from dormancy release to germination, degradation and enzymatic activity of macromolecules including soluble proteins in the endosperm where nutrients are stored. It provides material and energy for the completion of post-ripening of seed embryos, releasing dormancy and entering germination. The physiological change process and the morphological development process of seed embryos cooperate with each other to complete the germination of M. oleifera seeds. Seedlings have completed germination to form original cotyledon-shaped seedlings, the cotyledons only have the function of absorbing nutrients but not assimilating. |
| keywords:Malania oleifera seed germination seed post-ripening seed embryo morphology physiological changes seedling types |
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