Seed Development and Embryo Culture of Endangered Abies beshanzuensis

doi:10.11983/CBB21096

Abstract

Abstract:

The seed germination rate of Abies beshanzuensis is low, and the characteristics of seed development are elusive, which severely limit the natural regeneration of the population in situ. To illustrate the developmental characteris-tics of seeds and identify the main factors affecting seed development, this article aimed to study the number, weight, and microstructural characteristics of the embryo and endosperm of the seed in the female cones at different development stages, as well as the primary metabolites of the endosperm in the critical period of seed development. The results showed that July was a critical period for seed development of A. beshanzuensis. During this period, the endosperm weight increased rapidly and the carbohydrate metabolism in the endosperm was active. Anatomical and morphological analysis of the female cones showed that a large number of abnormally developed seeds appeared in cones in late July. Analysis of the primary metabolites of endosperm during the critical period showed that the content of trehalose-6-phosp-hate in the endosperm of abnormally developed seeds was significantly decreased. It was speculated that during the critical period of seed development, the decrease of trehalose-6-phosphate in the endosperm may be an important cause of abnormal seed development. Based on the characteristics of A. beshanzuensis seed development, we established the embryo culture technology for A. beshanzuensis, and generated test-tube plantlet.

Key words: Abies beshanzuensis, seed, embryo, endosperm, endangered mechanism, embryo culture

Ke Liu, Bin Liu, Lu Yuan, Hui Shuai, Yang Yang, Tingjin Wang, Deliang Chen, Xiaorong Chen, Kaibin Yang, Xiaofeng Jin, Liping Chen. Seed Development and Embryo Culture of Endangered Abies beshanzuensis[J]. Chinese Bulletin of Botany, 2021, 56(5): 573-583.

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URL: https://www.chinbullbotany.com/EN/10.11983/CBB21096

https://www.chinbullbotany.com/EN/Y2021/V56/I5/573

Figures/Tables 7

Figure 1 Diagram of the sampling of the cones and seeds of Abies beshanzuensis

Figure 2 Morphological changes of the micropylar funnel and pollen transfer during the pollination stage of Abies beshanzuensis (A) The integument develops a stigmatic micropylar funnel (arrow); (B) The pollen (arrow) attaches to the edge of micropylar funnel; (C) The integument folds inward and the micropylar funnel is closed (arrow); (D) The pollen (arrow) enters the pollen chamber. MF: Micropylar funnel; Po: Pollen; Poc: Pollen chamber. (A)-(C) Bars=100 μm; (D) Bar=500 μm

Figure 3 The endosperm rate and embryo rate of Abies beshanzuensis cones at different developmental stages in 2019 and 2020 (A) Changes of endosperm rate of A. beshanzuensis seeds with time; (B) Changes of embryo rate of A. beshanzuensis seeds with time. Different lowercase letters indicate significant differences at 0.05 level.

Figure 4 Changes in seed, embryo and endosperm weight of Abies beshanzuensis seeds at different developmental stages in 2019 and 2020 (A) Changes in the weight of seed with time in 2019 and 2020; (B) Changes in the weight of embryo and endosperm with time in 2019; (C) Changes in the weight of embryo and endosperm with time in 2020. Different lowercase letters indicate significant differences at 0.05 level.

Figure 5 Morphology of Abies beshanzuensis seed and its embryo and endosperm during development (A) The ovule on May 25th; (B) The embryo and endosperm of type I seeds on June 25th; (C) The endosperm of type II seeds on June 25th; (D) The paraffin section of the ovule on May 25th, the pollen (top) and archegonium (bottom) are in the red box; (E) The paraffin section of type I seeds on June 25th, the embryo in the red box; (F) The paraffin section of type II seeds on June 25th; (G) The embryo and endosperm of type I seeds on July 25th; (H) The endosperm of type II seeds on July 25th; (I) The shriveled tissue of endosperm or/and embryo within type III seeds on July 25th; (J) The paraffin section of type I seeds on July 25th, the embryo in the red box; (K) The paraffin section of type II seeds on July 25th; (L) The paraffin section of type III seeds on July 25th; (M) The embryo and endosperm of type I seeds on August 25th; (N) Type III seeds on August 25th; (O) The embryo and endosperm of type I seeds on September 25th. Bars=1 000 μm. MF: Micropylar funnel; In: Integument; Em: Embryo; Es: Endosperm; Po: Pollen; FG: Female gametophyte; Re: Resinocyst; Ext: Exotesta; Ent: Endotesta; Cy: Cotyledon; Hy: Hypocotyl; Su: Suspensor system; ST: Shriveled tissue; ER: Embryo root; CC: Corrosion cavity

Figure 6 Changes of primary metabolites in endosperm of Abies beshanzuensis in June and July (A) Differential metabolites of normal endosperm in June and July; (B) The proportion of key difference metabolites in the first, fourth, and fifth models in the same change pattern in all metabolites and the proportion of the same metabolites tested in all samples; (C) Relative content of melibiose, trehalose-6-phosphate and methylmaleic acid in endosperm of A. beshanzuensis seeds in June and July. 6_NE: Normal endosperm in June; 7_NE: Normal endosperm in July; 7_AE: Abnormal endosperm in July. Different lowercase letters indicate significant differences at 0.05 level. FC: Fold change; LPC: Lysophosphatidylcholine; LPE: Lysopnosphatidylethanolamine; PC: Phosphatidylcholine

Figure 7 Changes in germination rate of embryo of Abies beshanzuensis seeds at different developmental stages (A) Embryo germination (bar=200 μm); (B) Seedlings obtained by embryo culture (bar=2 cm); (C) Changes in germination rate of embryo of A. beshanzuensis seeds at different developmental stages. Different lowercase letters indicate significant differences at 0.05 level.

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