(Download PDF) Orchid Propagation From Laboratories To Greenhouses Methods and Protocols Yung I Lee Online Ebook All Chapter PDF
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Yung-I Lee
Edward Chee-Tak Yeung Editors
Orchid Propagation:
From Laboratories
to Greenhouses—
Methods and Protocols
Springer Protocols Handbooks
Edited by
Yung-I Lee
Biology Department, National Museum of Natural Science, Taichung, Taiwan, Republic of China
This Humana press imprint is published by the registered company Springer Science+Business Media, LLC
part of Springer Nature.
The registered company address is: 233 Spring Street, New York, NY 10013, U.S.A.
Preface
The orchid family is one of the largest families of flowering plants known for their beauty
and economic importance. Orchids are especially vital to the horticulture and florist indus-
tries. In addition, the potential of using orchids as a source for the pharmaceutical and
fragrance industries is currently being explored, resulting in a steady increase in scholarly
publications related to orchid biology research. When looking at the literature available, it
is surprising to find that there is no comprehensive integration of key areas of research that
are important to both scientists and commercial growers alike.
The main purpose of this publication is (1) to provide key practical areas of research (i.e.
germination, micropropagation, traditional and current techniques related to plant improve-
ment) and (2) to document methods that ensure survival of plants from laboratories to green-
houses. The topics highlighted in this work is by no means complete but is meant to draw
attention to the many techniques available that can be beneficial to one’s work on orchid research
and development. We hope that this publication can promote cross-talks between scientists and
growers. Both groups have different knowledge bases and when combined will ensure successful
growth of orchids in their natural habitats or commercial greenhouses. Laymen that are inter-
ested in orchid growing will also benefit from having this handy scientific reference.
In this work, we emphasize both the theoretical understanding of methods and practi-
cal details. A proper theoretical understanding is essential to the success of a protocol.
Hence several overview chapters have been included amongst the protocol chapters. We
first emphasize propagation methods using seeds and related techniques that are important
to plant conservation and improvement (Part I). Successes in asymbiotic and symbiotic
seed germination are keys to orchid conservation and their propagation. Part II summa-
rizes micropropagation methods, common media, and newer methods of micropropaga-
tion such as the bioreactor culture procedures. This is followed by a special technique
section (Part III) focusing on techniques related to the manipulation of explants in an
in vitro environment. Some cell biological methods and transformation techniques are
included in Part IV. Plant improvements through transformation are now common and can
also be applied to orchid species with some successes; however, transformation protocols
can apply only to a limited number of orchid species. The methods and protocols detailed
serve to encourage further improvements in this area of research. Successes in a laboratory
setting do not guarantee plant survival and propagation in greenhouses and in the natural
environment. Hence, in Part V, we focus on greenhouse propagation techniques that are
essential to the survival of plants generated from a laboratory setting. A final part is to
showcase recent successes on orchid propagation by documenting sample publications and
how to present orchids in an artistic fashion for one’s enjoyment.
We would like to thank Mr. Colin Chan for his help in editing the figures and graphics
and to Professor C.C. Chinnappa for proofreading manuscripts. Finally, we are grateful to
all authors for their contributions to this book and their patience and cooperation during
the course of preparation and editing.
v
Contents
Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
vii
viii Contents
Index��������������������������������������������������������������������������������������������������������������������������������� 521
Contributors
ix
x Contributors
Abstract
In this overview, the development of orchid seed and protocorm is summarized. Although the structural
organization of seed and protocorm appears simple, information is presented indicating that they have
developmental programs similar to and as complex as other flowering plants. The varied suspensor
morphologies, the presence of cuticular material covering the surface of the embryo, and the delicate seed
coat structure ensure embryo survival, albeit unusual. The embryo is programmed to form a protocorm.
The protocorm cells are destined to form a shoot apical meristem at the apical (chalazal) end and to house
the symbiont at the basal (micropylar) end of a protocorm. Changes in protocorms during asymbiotic and
symbiotic seed germination are discussed.
Key words Embryo, Suspensor, Symbiotic seed germination, Asymbiotic seed germination,
Endosperm, Seed storage proteins and lipids, Phytohormones, Mycorrhizal fungi, Seed coat,
Carapace, Protocorm, Shoot apical meristem
1 Introduction
Yung-I Lee and Edward Chee-Tak Yeung (eds.), Orchid Propagation: From Laboratories to Greenhouses—Methods
and Protocols, Springer Protocols Handbooks, https://doi.org/10.1007/978-1-4939-7771-0_1,
© Springer Science+Business Media, LLC, part of Springer Nature 2018
3
4 Edward C. Yeung et al.
2.1 The Embryo In orchids, after a successful pollination and fertilization event,
numerous seeds develop within a single capsule. Seeds are very
small and embryos have no obvious histodifferentiation into distinct
tissues, such as the root and shoot apical meristem, primary meri-
stems, and organ, i.e., cotyledon. An extensive review by Yam et al.
[12] documents embryo features from various groups of orchids
and this information will not be repeated here; instead, essential
developmental characteristics are featured below.
2.1.1 Suspensor In flowering plants, the zygote usually divides unequally, giving rise
to a larger basal cell and a smaller terminal cell. The basal cell gives
rise to a short-lived embryonic organ, known as the suspensor, and
the smaller terminal cell divides and gives rise to the embryo proper
[23]. One of the most notable features in orchid embryos is the
varied morphologies of the suspensor found in different groups of
orchids [1]. The number of suspensor cells when present tends to be
limited, ranging from 1 to over 30 [10]. Depending on the species,
the suspensor can appear as a single enlarged cell or as a multicellular
structure with varied forms [1] (Fig. 1). However, it is important to
note that not all orchid species have a distinct suspensor. For exam-
ple, many species in the genus Spiranthes are considered to be sus-
pensorless, as the basal cell fails to enlarge and divide further and
resembles an embryo proper cell [1, 10, 12] (Fig. 1a). Although the
structure of the suspensor appears simple, such as the single suspen-
sor cell of the nun orchid, Phaius tankervilleae, dramatic changes in
Fig. 1 Varied suspensor morphologies. (a) Spiranthes sinensis embryos without a suspensor. Scale bar = 60 μm.
(b) A Phaius tankervilleae embryo showing a single, enlarged suspensor cell. Scale bar = 80 μm. (c) A Cypripedium
debile embryo with a single, small suspensor cell. Scale bar = 60 μm. (d) A Bletilla formosana embryo showing
filamentous extensions originating from an enlarged basal suspensor cell. Scale bar = 120 μm. (e) The suspensor
of Calypso bulbosa embryo consists of an enlarged cell and a 4-celled filamentous region. The basal suspensor
cell extends toward the embryo proper resulting in the formation of a U-shaped embryo. Scale bar = 60 μm. (f)
Cymbidium sinense embryo showing multidirectional growth of suspensor cells. Scale bar = 200 μm. (g) An
Epidendrum ibaguense embryo showing the long multicellular suspensor. Scale bar = 120 μm
6 Edward C. Yeung et al.
size and shape can occur during its course of development (Fig. 1b).
The morphogenetic changes involve coordinated rearrangement in
cell cytoskeleton [24]. Changes in the microtubules have also been
found during the course of suspensor and proembryo formation in
Cymbidium sinense [25]. At present, few detailed cellular and ultra-
structural studies of orchid embryos are available in the literature.
Additional studies are needed in order to obtain insight into how the
varied suspensor forms are generated. It is likely that the cytoskeletal
elements, i.e., microtubules and actin filaments, are involved in the
morphogenesis of suspensors.
The varied morphologies of the suspensor and the haustoria-
like behavior indicate that they can play a role in nutrient uptake.
In Paphiopedilum delenatii, when the suspensor cells are examined
using an electron microscope, the cells have a transfer cell mor-
phology with wall ingrowths present [26]. The increase in surface
area through the formation of convoluted wall ingrowths enables
an increased capacity for nutrient uptake. It is generally accepted
that cells with wall ingrowths are highly specialized [27] and func-
tion in short distance transport [28, 29].
Based on histochemical staining using toluidine blue O [30],
lipidic polymers, i.e., cutin and suberin, and phenolic substances,
such as lignin, are absent from the suspensor cell wall. In the
absence of these deposits, the primary wall of the suspensor cells
remains “porous” and permits the transfer of nutrients from the
maternal seed coat to the suspensor. For species without any obvi-
ous structural specialization in the suspensor, such as the nun
orchid, the plasmolysis and tracer uptake studies by Lee and Yeung
[31] clearly demonstrated that the suspensor has unique physio-
logical properties. It was determined that the osmotic potential of
the suspensor cell in nun orchid is more negative than surrounding
cells. The differences in osmotic potentials can direct a preferential
flow of water into the suspensor. When introducing a fluorescent
tracer 6-carboxyfluorescein diacetate (CFD) to developing seeds,
the fluorescence signal carboxyfluorescein, a hydrolyzed product
of CFD, is first detected in the suspensor cytoplasm prior to its
appearance in the embryo proper [31]. These results clearly indi-
cate that the suspensor is the uptake site for the developing embryo.
Not all orchid species have a distinct suspensor [3, 10].
Although the nutrient uptake pathway by the suspensorless embryo
is not known, it is logical to speculate that the entire surface of the
embryo proper must be able to absorb nutrients from surrounding
maternal tissues. In Cyrtosia javanica, the seed coat is multilayered
and remains intact until seed maturation [32]. Dense cytoplasmic
accessory and antipodal cells are present, locating at the chalazal
end of developing seeds [32]. It is interesting to note that although
a cuticle is present, it has a patchy appearance and it is initially
absent from the wall of the embryo at the chalazal end [32]. The
pattern of cuticle deposition suggests that the entire surface of the
Understanding Seed and Protocorm Development in Orchids 7
2.1.2 Embryo Proper In a majority of flowering plants, the embryo proper undergoes
distinct phases of development. After establishing the apical-basal
polar axis, histodifferentiation of major tissues takes place, fol-
lowed by storage product deposition, preparation of germination
programs, and final changes leading to developmental arrest [33,
34]. The histodifferentiation phase in flowering plants is responsi-
ble for laying down the future body plan of the sporophyte, ready
for germination. Distinct primary meristems, i.e., protoderm,
ground meristem, and procambium, and the root and shoot apical
meristems are clearly delineated at the end of the histodifferentia-
tion phase. Upon germination, a seedling forms quickly due to the
activities of the “pre-formed” apical meristems. Orchid embryo is
minute in size, with no obvious tissues and organ. Casual examina-
tion would lead to the conclusion that a histodifferentiation phase
does not exist in orchid embryos.
Not having an easily recognizable tissue pattern an orchid
embryo does not necessarily suggest that it is less specialized when
compared to other flowering plants. The following observation
indicates that histodifferentiation has indeed occurred during early
embryogenesis in orchid. In examining the structural organization
of the embryo proper, a gradient of cell size is often present with
smaller cells located at the future shoot pole (Fig. 2a). The gradi-
ent indicates that physiological differences exist among embryo
cells in an apical-basal manner. This is demonstrated by the fact
that upon germination, the smaller cells at the apical (chalazal) end
are destined to form the meristematic zone and the large cells at
the basal (micropylar) end will enlarge and destined to house the
symbiont. In orchids, the surface layer of the embryo is specialized,
taking on an epidermal cell characteristic. A surface cuticle layer
has been reported in other flowering plant embryos [35, 36] and
similar cuticular depositions can also be found in orchids (Fig. 2b).
In Phalaenopsis amabilis [37] and Cyrtosia javanica [32], a cuticle
is present but it takes on a patchy appearance. In Cymbidium
sinense, the surface cuticle layer is very distinct covering the entire
surface of the embryo proper [38]. The ability to synthesize cutic-
ular materials is an epidermal cell characteristic, a specialized fea-
ture of a protoderm. Finally, the structural organization of an
orchid embryo mirrors the structure of a protocorm at the time of
germination. In orchid, immature seeds can germinate asymbioti-
cally to form protocorms, once they reach approximately half way
into seed maturation prior to storage product synthesis. The ability
to germinate precociously indicates that the protocorm body plan
8 Edward C. Yeung et al.
Fig. 2 Some structural characteristics of embryo proper. (a) Embryo proper of Epidendrum ibaguense showing
a gradient of cell size with small cells occupying the future shoot pole (*). Scale bar = 100 μm. (b) The embryo
proper of Cyrtosia javanica showing the presence of a distinct cuticle (arrowhead) on its surface. Scale
bar = 100 μm. (c) The nun orchid, Phaius tankervilleae, at the time of maturation. The embryo cells have an
abundant lipid deposits (arrowhead). Scale bar = 40 μm. (d) A section of Vanilla planifolia seed, showing the
unusual thick seed coat (*). Scale bar = 0.3 mm. (e) A Cypripedium plectrochilum seed showing a thick layer
of carapace (arrowhead) that wraps around the embryo. Scale bar = 100 μm. (f) Phenolic deposits can be
present in the carapace and these deposits are readily detected using a fluorescence microscope. Scale
bar = 100 μm
20 Edward C. Yeung et al.
4 Future Perspectives
JASKA. Ei, ei! Minä vaan, että onko se oikein ulkomaaa verkaa?
EPRA. Ja rahakirstu!
EPRA. Ha, oli sanonut, oli sanonut… Kyllä minä sen asian
paremmin tiedän. Hölmölän vanhat ihmiset tietävät kertoa, että
minun taatani taata sen omisti.
JASKA. Ja minun isääni harmitti se, että sinun isäsi kuoli ennen,
siitä harmista otti ja kuoli.
JASKA. Kultasapeli.
EPRA. Ja rahakirstu.
JASKA. Mikäs tuo korea mies on, jolla on kukon pyrstö päässä.
EPRA. Kyllä Akianteri on yhtä hyvä kuin joku muukin, pysy sinä
Amalia säädyssäsi.
EPRA. Maa-asiasta?
EPRA. Niin, kun minä sitä asiaa tuumailen, niin suostun minäkin
siihen.
JASKA. Sanokaahan minulle kahden kesken, onkos tässä
aarretta?
EPRA. Johorimuikkus!
JASKA. Johorimuikkus!
MAAILMAN-MATTI. Se on hepreiskaa!
EPRA. Hää!
EPRA. Niin, nyt tuli talooni makian leivän päivät. En minä enään
viitsi makkaratikkuja veistellä.
AKIANTERI.
Esirippu.
TOINEN NÄYTÖS.
JASKA. Mutta sepäs oli sukkela temppu, minä teen heti saman
tempun, minulla on vielä pönttöössä kultamaalia, jolla minä maalasin
"keisarin saunapiippuni". — En minä viitsi maalata taloani mutta
posliinipiippuni pitää aina olla kullattu, se on paras piippu koko
Hölmölässä, ja Epran käy sitä niin kateeksi, ai, niin kateeksi — Mutta
sanokaas, minkästähden te niin komiasta kodosta läksitten?