🧬 Endosperm culture

This lesson explains the core ideas, methods, and exam-relevant applications for this topic in plant biotechnology. Focus on definitions, process steps, and practical uses for revision.

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In angiosperms the endosperm is the main nutritive tissue for the embryo. The

endosperm is the product of double fertilization during which out of the two male gametes, one

fertilizes the egg to form zygote and other fuses with secondary nuclei to form triploid

endosperm. Hence, triploid nature of endosperm is the characteristic feature of angiosperms.

Both mature and immature endosperm can be used for culture initiation. A key factor for the

induction of cell divisions in mature endosperm cultures is the initial association of embryo but

immature endosperms proliferate independent of embryo. The endosperm tissue often shows a

high degree of chromosomal variations and polyploidy. Mitotic irregularities, chromosome

bridges and laggards are the other important characteristics of endosperm tissues. Triploids are

usually seed sterile and is undesirable for plants where seeds are commercially useful.

However, in cases where seedlessness is employed to improve the quality of fruits as in

banana, apple, citrus, grapes, papaya etc. the induction of triploid plants would be of immense

use. Triploid plants have more vigorous vegetative growth than their diploid counterparts.

Hence, in plants where the vegetative parts are economically useful, triploids are of good use.

The endosperm is a homogenous mass of parenchymatous tissue lacking in vascular elements.

Since the endosperm tissue lacks in differentiation into specialised tissue and vascular element

their utility in the study of experimental morphogenesis is well appreciated. Attempts to grow

endosperm under in vitro condition dates back to 1930 by the scientist Lampe and Mills. The

young corn endosperm was cultured on the extract of potato or young corn by the above

scientist and slight proliferation of tissue was noticed from the tissues surrounding the embryo.

In 1947, LaRue, successfully cultured the corn endosperm and obtained plantlets with root

shoot axis and miniature leaves. Several investigators, since then, have cultured the endosperm

tissue but invariably have failed to induce organogenesis. However, successfully organogenesis

was achieved from endosperm callus tissue of Ricinus communis, Oryza sativa and Pyrus

malus .

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Corn endosperm

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Callus induction from endosperm

During the early period of endosperm culture, there was difficulty in establishing callus induction

from mature endosperm. Of late successfully regeneration of triploid plantlets are being

achieved. The process of regeneration may be direct from the endosperm or via callus stage.

Callus tissue is induced from the endosperm explant in usual manner as with other explant. The

endosperm tissue is homogenous in nature surrounded by a single peripheral layer of

meristematic cells. These meristematic cells undergo repeated periclinal and anticlinal divisions

resulting in increased girth of endosperm tissues and in turn producing callus with nodular

structures on the surfaces or just below the outer most layer. The plants, which have so far

responded favourably, belong to the families of Euphorbiaceae, Loranthatceae and

Santalaceae . With respect to members of first two families the embryo has to be maintained

intact along with endosperm in culture, to induce the callus from the endosperm. In these cases,

immediately after the callus induction from the endosperm the embryo should be removed under

aseptic conditions to avoid the formation of embryo-endosperms callus mixtures. The essentially

of the initial association of the embryo endosperm for inducing proliferation is that during

germination of the embryo, it releases gibberellin - like substances which turn in help in de novo

synthesis of other enzymes responsible for the endosperm proliferation. These substances are

otherwise called `embryo factors'.

The age of endosperm is critical factor influencing proliferation of endosperm tissue. Endosperm

cultured immediately after pollination normally do not proliferate. In crops like rice, maize,

endosperm proliferates 7 to 8 days respectively after pollination. In many cases, endosperm of

cellular nature proliferates more easily than nuclear endosperm or coenocytic endosperm. In

some species the culture of endosperm with their embryo produced favourable condition for the

proliferation of endosperm whereas in species like Taxillus verstitus, culture of endosperm after

cutting it into two species produced better results. In endosperm culture, the proliferation thus

induced occurs at different duration and it is a genotype dependent phenomenon. For example,

the endosperm of Ricinus communis proliferated 10 days after culture whereas the endosperm

of Pyrus malus and Santalum took 15 to 21 days respectively for proliferation.

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Morphogenesis of endosperm callus

Straus (1954) stated that the endosperm tissue has passed through approximately 95

transfers and has produced an estimated 15 kilograms of tissue. Not a single example of

complex differentiation was observed during the period. However, both organogenesis and

somatic embryogenesis were observed, in other cases. The first convincing evidence of organ

formation was from Exocarpus cupriformis . The incidence of organogenesis from the above

species was noticed in the form of shoot buds all over the surface of the endosperm. Apart from

the direct organogenesis in the form of buds, the organogenesis may also follow the pathway

via the callus stage. The formation of shoot buds increased with increase in cytokinin

concentration and decrease in auxin concentration. In general, endosperms of all the plant

species showed increased bud formation with response to higher concentration of cytokinin.

The studies on the role of auxin (IAA) and cytokinin (kinetin) revealed that cytokinin alone was

more effective in combination with auxin: there was no differentiation in the absence of

cytokinin, but cytokinin is not always necessary to induce bud formation from normal tissue. But

for endosperm tissues to produce buds cytokinin is required. Presence of organic additives like

tomato juice, coconut milk, casein hydrolysate, yeast extract in the culture medium enhanced

endosperm proliferation and regeneration.

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Application of endosperm culture

The cultured endosperm forms an excellent experimental system for physiological and

morphogenetic studies. This system shows great promise in the study of metabolism and

differentiation. The triploidy can be exploited in the crops viz . apple, banana, mulberry,

sugarbeet, tea and watermelon where seeds are not of commercial importance. In some plants

especially in clonally propagated ones triploids are superior to the diploids giving better pulp

woods. Since these plants can be propagated vegetatively seed sterility is not a severe setback.

In the case of conventional method of triploid production, crosses are made between auto

tetraploids and diploids. Sometimes, these crosses may not be successful causing difficulty in

triploid production.

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Nature of impairments in embryo development and causes

Causes	Source	Example
Normal initial rate of growth followed by retardation in later stage	Embryo	Oenothera biennis x O. muricta O. biennis x_O.lamarkiana_
Paucity of cell organelles due to lower synthetic capacity of hybrid genome, necrosis and dumping	Embryo	Hibiscus costatus x H. aculeatus H. costatus x_H. furcellatus_
Hybrid failure due to pollen incompatibility	Pollen incompatibility	Pinus pence x_P. cembra_ P. strobus x_P. flexilis_
Disintegration of endosperm soon after fertilization	Endosperm	Oenothera and_Gossypium_
Vacuolation in endosperm cells at chalazal and not followed by further cell division	Endosperm	Lycopersicon pimpinellifolium x L. peruvianum
Abnormal behaviour of antipodals and preventing nutrient supply to embryos	Endosperm	Citrus (2x) / Citrus (4x) Gossypium hirsutum x _G. _ arboreum
Intrusive growth of somatic tissue causing somatoplastic sterility	Nucellus	Nicotiana rustica x N. tabacum N. rustica x_N.glutinosa_
Non-differentiation of integumentary cells into connective tissues to connect main vascular bundle with chalazal tissue	Integuments	Nicotiana hybrids

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Examples of wide crosses

Wide crosses	Purpose
Corchorus capsularis x_C. olitorius_	Hybrids had fibres with quality of_C. capsularis mand strength of_C. olitorius
Hordeum vulgare x_H. bulbosum_	The hybrids possessed winter hardines and mildew resistance like_H. bulbosum_
Lycopersicon esculentum x_L. peruvianum_	The hybrids possessed resistance to viruses,molds and nematodes along with good fruit set like_L. peruvianum_
Melilotus officianalis x_M. alba_	Hybrids resembling M. officinalis in agronomic characters and low coumarin content like_M. alba_
Nicotiana tabacum x_N. resophilia_	To get plants with resistance to black shank
Oryza sativa x_O. officinalis_	To transfer pest resistance
Trifolium pratense x_T. sarosiense_	To impart perennial plant habit to red clover

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Questions

1. Endosperm is …………… in nature

a). Triploid b). Tetraploid c). Monoploid d). Diploid

2. Endosperm is product of …………… fertilization

a). Double b). Single c). Triple d). None of the above

3. Triploid nature of endosperm is the characteristic feature of

a). Angiosperms b). Gymnosperm c). Pine d). None of the above

4. The important characteristics of endosperm tissues are …….…..

a). Chromosomal variations b). Polyploidy

c). Chromosome bridges and laggards d). All the above

5. Successfull organogenesis was achieved from endosperm callus tissue of …….…..

a). Ricinus communis b). Oryza sativa

c). Pyrus malus d). All the above

6. Endosperm culture is successful in …….…..

a). Euphorbiaceae b). Santalaceae

c). Loranthatceae d). All the above

7. Triploidy is exploited in ………….

a). Apple b). Banana

c). Watermelon d). All the above

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Additional sources

http://www.youtube.com/watch?v=Gq8NWh98wQs&feature=related - video

http://www.tutorvista.com/content/biology/biology-iii/angiosperm-morphology/fertilization.php

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Summary Cheat Sheet

Quick Recall Points

• Define key terms in one line and revise their use in plant biotechnology.
• Memorize major steps, methods, and applications covered in this lesson.
• Practice exam-style distinctions between related concepts and techniques.

Exam Traps

• Do not confuse similar terms without checking context and biological level.
• Revise process order carefully; sequence-based questions are common.
• Link each method with its most likely application question.

References

1 source • [1]

[1]

Standard BSc Agriculture Plant Biotechnology notes

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