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A review of the seed biology of Paeonia species (Paeoniaceae), with particular reference to dormancy and germination

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Main conclusion Most Paeonia species have epicotyl dormancy. Germination of peony seeds requires warm stratification for embryo growth and radicle protrusion followed by cold stratification for epicotyl growth. The genus Paeonia (Paeoniaceae) includes many popular ornamentals, has colorful flowers and contains several Chinese medicinal species. The germination protocol for seeds of Paeonia species is complex and impedes the breeding of new cultivars and contributes to the rarity and high cost of the plants. Although numerous reports on seed dormancy/germination in peonies are scattered throughout the literature, most of them are in Chinese. The primary aims of this paper are to provide a general overview of the available information on seed dormancy/germination in peonies and to make some suggestions regarding propagation for the peony industry and breeders. Most Paeonia species have epicotyl dormancy. The embryo is differentiated into organs, but it is underdeveloped (small) and must grow inside the seed before the radicle can emerge. Germination of peony seeds requires warm stratification for embryo growth and radicle protrusion followed by cold stratification for epicotyl growth. In addition, the epicotyl is sensitive to cold stratification only after the root has grown to a certain length. GA3 treatment enhances embryo growth and subsequent germination percentages. Further investigations on the physiology, genetics and proteomics would contribute to a better understanding of seed dormancy in Paeonia.
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Vol.:(0123456789)
1 3
Planta (2019) 249:291–303
https://doi.org/10.1007/s00425-018-3017-4
REVIEW
A review oftheseed biology ofPaeonia species (Paeoniaceae),
withparticular reference todormancy andgermination
KeliangZhang1· LinjunYao1· YinZhang1· JerryM.Baskin2· CarolC.Baskin2,3· ZuomingXiong1,4· JunTao1
Received: 11 June 2018 / Accepted: 23 September 2018 / Published online: 1 October 2018
© Springer-Verlag GmbH Germany, part of Springer Nature 2018
Abstract
Main conclusion Most Paeonia species have epicotyl dormancy. Germination of peony seeds requires warm stratifica-
tion for embryo growth and radicle protrusion followed by cold stratification for epicotyl growth.
The genus Paeonia (Paeoniaceae) includes many popular ornamentals, has colorful flowers and contains several Chinese
medicinal species. The germination protocol for seeds of Paeonia species is complex and impedes the breeding of new cul-
tivars and contributes to the rarity and high cost of the plants. Although numerous reports on seed dormancy/germination in
peonies are scattered throughout the literature, most of them are in Chinese. The primary aims of this paper are to provide
a general overview of the available information on seed dormancy/germination in peonies and to make some suggestions
regarding propagation for the peony industry and breeders. Most Paeonia species have epicotyl dormancy. The embryo is
differentiated into organs, but it is underdeveloped (small) and must grow inside the seed before the radicle can emerge. Ger-
mination of peony seeds requires warm stratification for embryo growth and radicle protrusion followed by cold stratification
for epicotyl growth. In addition, the epicotyl is sensitive to cold stratification only after the root has grown to a certain length.
GA3 treatment enhances embryo growth and subsequent germination percentages. Further investigations on the physiology,
genetics and proteomics would contribute to a better understanding of seed dormancy in Paeonia.
Keywords Cold stratification· Endogenous plant hormones· Epicotyl morphophysiological dormancy· Paeonia· Seed
dormancy/germination· Warm stratification
Introduction
Paeonia, the only genus of the Paeoniaceae and previously
included in the Ranunculaceae, has been cultivated in China
since the Han dynasty, for more than 2000years (Liu etal.
1987; Sang etal. 1997; Hong etal. 2017). It is among the
most popular garden plants in temperate regions and has been
named the “king of flowers” and “flowers of richness and
honor” in China (Liu etal. 1987; Sang etal. 1997). The genus
is taxonomically complex, consisting of 25–33 species (15
in China including 10 endemic species) (Rogers 1995; Hong
etal. 2001) and more than 3000 cultivars (Fig.1) (Liu etal.
1987). Three sections are recognized within Paeonia (Stern
1946): section Oneapia, two herbaceous species endemic to
Pacific North America; section Moutan, six shrub species in
central and western China; and section Paeonia, about 27 her-
baceous species distributed disjunctly in eastern Asia, central
Asia, the western Himalayas and the Mediterranean region
(Sang etal. 1997). Sections Oneapia and Moutan contain only
diploid species, while one-third of the species in section Paeo-
nia are tetraploids (Stern 1946). Hong etal. (2017) reviewed
the status of wild peony species in section Moutan based on
the history of field surveys and investigations. They found
that P. cathayana and P. ostii each survive as only one indi-
vidual; P. decomposita, P. qiui, P. rockii and P. rotundiloba are
endangered; and P. jishanensis and P. ludlowii are vulnerable.
* Jun Tao
taojun@yzu.edu.cn
1 Jiangsu Key Laboratory ofCrop Genetics andPhysiology,
College ofHorticulture andPlant Protection, Yangzhou
University, Yangzhou225009, People’sRepublicofChina
2 Department ofBiology, University ofKentucky, Lexington,
KY40506, USA
3 Department ofPlant andSoil Sciences, University
ofKentucky, Lexington, KY40546, USA
4 Guangling College, Yangzhou University, Yangzhou225009,
People’sRepublicofChina
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
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