Tracheids: Normal And Reaction Wood
Gymnosperm tracheids have a relatively safe structural design compared to angiosperm vessels, as they are thick walled for good structural support and have a large number of pits with wide apertures that allow for rapid refilling via replacement of air by water , 20, and 26).94 However, they also have comparatively narrow water conduits, limiting their conductive efficiency, which can adversely affect growth rate.98,99 The large percentage of tracheids 95 and overall high wood density also reduces storage capacity, for example, of photosynthates, metabolites, and so forth, in the SW of gymnosperm trunks.98 However, because gymnosperm woods are mainly composed of tracheids, this functional redundancy can often limit deleterious effects of either injury or disease.97 Furthermore, gymnosperm tracheid structure and wood density may actually give them an advantage under water stress conditions, such as either in drought-stricken or arid environments, or with very tall trunks, in which water stress can result under conditions of very long distance transport.99
Figure 29. Artistic depictions of lignin structure as envisaged by Brunow et al.105 and monolignols 1416.
E. Pacini, in, 2015
Propagation Of Cloned Lines
Based on the early work of Steward on carrot, plants can now routinely be produced through somatic embryogenesis. Table 1 indicates a list of species where this technique has been successfully applied. Woody as well as nonwoody plants can be propagated from somatic material giving rise to clones of selected genotypes of high economical value. The superiority of this in vitro propagation technique over others such as microcuttings, bud culture, or organogenesis is its efficiency, associated with the high conformity of the produced clones respective to the donor parent. This conformity is due to the unicellular origin of the somatic embryo in contrast to the pluricellular origin of organogenic buds, which arise from the structural reorganization of dedifferentiated somatic cells into meristems, which thereafter develop into shoots.
Table 1. A nonexhaustive list of species successfully regenerated into entire plants by somatic embryogenesis
Multiple somatic embryos coming from one immature embryo can be produced from subsequent production runs, then pooled together and stored until sufficient numbers have been produced. Culture batches can be set continuously throughout the year.
The cryopreserved embryos can be recovered when necessary and can be made to germinate synchronously to provide plants of uniform age and size during the suitable growing season.
Bharti Sharma, Elena M. Kramer, in, 2018
What Are The Characteristics Of Gymnosperms
As vascular plants, gymnosperms have two types of vascular tissues: xylem and phloem. The xylem transports water, while the phloem transports sugars and other organic nutrients to different parts of the plant.
In angiosperms, xylem tissues consist of vessel elements, parenchyma, and tracheids. Parenchyma are living cells responsible for metabolic functions, tissue damage repair, and starch storage. While vessel elements and tracheids are conducting cellsthat are dead at maturity. Conducting cells are cells that act like pipes, transporting fluids from one area to another. While vessel elements have thin walls, tracheids have thick secondary cell walls stiffened by a substance called lignin.
With the exception of gnetales , gymnosperms lack vessel elements and only have tracheids.
The bracts of a gymnosperm cone are called sporophylls. Sporophylls are arranged around a central stalk. This arrangement is called strobilus . When mature, the seeds of some species are enclosed in sporophyte tissue called integument.
Sporophylls are modified leaves that produce sporangia.
Sporangia are sac-like structures in which spores are produced.
Male pollen cones called microstrobili have small leaves called microsporophylls. Pollen sacs called microsporangia are found on the lower surface of microsporophylls. On the other hand, female ovulate cones called megastrobili have many scales called megasporophylls, each containing megasporangia.
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What Are Gymnosperms How Do They Differ From Angiosperms
Gymnosperms are a diverse group of vascular plants whose seeds are not enclosed in an ovary.
Recall that vascular plants are those with specialized tissues that transport water and nutrients to various parts of the plant. Vascular plants can be divided into higher and lower vascular plants: higher vascular plants produce seeds, while lower vascular plants do not.
Higher vascularplantscan be further divided into angiosperms and gymnosperms.
The Life Cycle And Reproduction Of Gymnosperms
An alternation of generations characterizes the life cycle of gymnosperms: haploid and diploid generations alternately produce each other .
Diploid means having two sets of chromosomes , while haploid means having a single set of chromosomes. The diploid nonsexual phase of a plant is called sporophyte, while the haploid sexual phase of the plant is called a gametophyte.
The sporophyte generation of the gymnosperm is more dominant than its gametophyte generation.
Diploid cells within the microsporangia undergo meiosis to produce haploid microspores. The microspore eventually germinates within the microsporangium, forming the male gametophyte . At this stage, the plant sheds pollen, which is then transported by wind or insects.
Similarly, a diploid cell within each megasporangium undergoes meiosis, resulting in four haploid megaspores, three of which degenerate, while the remaining one undergoes mitosis to form the female gametophyte. This prepares the ovule for fertilization.
Before fertilization, the pollen must first be transported to the female gametophyte in a process called pollination.
In the female megasporangium of many gymnosperms, a small pore exudes a sticky “pollination droplet” that traps pollen grains. The droplet is reabsorbed into the megasporangium for fertilization. In other species, pollen grains settle and grow on the surface of the megasporangium.
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Structure Growth And Development
Most of the solid material in a plant is taken from the . Through the process of , most plants use the energy in to convert from the atmosphere, plus , into simple . These sugars are then used as building blocks and form the main structural component of the plant. , a green-colored, -containing is essential to this process it is generally present in plant , and often in other plant parts as well. , on the other hand, use the resources of their host to provide the materials needed for metabolism and growth.
Plants usually rely on soil primarily for support and water , but they also obtain of , , , magnesium and other elemental from the soil. and plants depend on air and nearby debris for nutrients, and supplement their nutrient requirements, particularly for nitrogen and phosphorus, with insect prey that they capture. For the majority of plants to grow successfully they also require in the atmosphere and around their roots for . Plants use oxygen and to provide energy. Some plants grow as submerged aquatics, using oxygen dissolved in the surrounding water, and a few specialized vascular plants, such as and reed , can grow with their roots in conditions.
Life Cycle Of A Conifer
Pine trees are conifers and carry both male and female sporophylls on the same mature sporophyte. Therefore, they are monoecious plants. Like all gymnosperms, pines are heterosporous and generate two different types of spores: male microspores and female megaspores. In the male cones, or staminate cones, the microsporocytes give rise to pollen grains by meiosis. In the spring, large amounts of yellow pollen are released and carried by the wind. Some gametophytes will land on a female cone. Pollination is defined as the initiation of pollen tube growth. The pollen tube develops slowly, and the generative cell in the pollen grain divides into two haploid sperm cells by mitosis. At fertilization, one of the sperm cells will finally unite its haploid nucleus with the haploid nucleus of a haploid egg cell.
Figure 1 illustrates the life cycle of a conifer. The sporophyte phase is the longest phase in the life of a gymnosperm. The gametophytes microspores and megasporesare reduced in size. It may take more than year between pollination and fertilization while the pollen tube grows towards the megasporocyte , which undergoes meiosis into megaspores. The megaspores will mature into eggs .
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What Is Example Of Gymnosperm
Gymnosperms are vascular plants of the subkingdom Embyophyta and include conifers, cycads, ginkgoes, and gnetophytes. Some of the most recognizable examples of these woody shrubs and trees include pines, spruces, firs, and ginkgoes.
Is a flower an angiosperm?
Angiosperms, which are flowering plants, are the largest and most diverse group within the kingdom Plantae. With around 300,000 species, they represent approximately 80 percent of all the known green plants now living.
Which is the best definition of an angiosperm?
Angiosperm : any of the flower-producing plant. Angiosperms make up the division Magnoliophyta belonging to Subkingdom Embryophyta of the Kingdom Plantae. Etymology: from Greek angeîon, meaning receptacle + spérma, meaning seed.
Current Definitions Of Plantae
When the name Plantae or plant is applied to a specific group of organisms or , it usually refers to one of four concepts. From least to most inclusive, these four groupings are:
|Plants in the strictest sense include the , , , and , as well as fossil plants similar to these surviving groups (e.g., Metaphyta Whittaker, 1969|
|Plantae||Plants in a strict sense include the , and land plants that emerged within them, including . The relationships between plant groups are still being worked out, and the names given to them vary considerably. The Viridiplantae encompasses a group of organisms that have in their , possess a and b and have bound by only two membranes that are capable of photosynthesis and of storing starch. This clade is the main subject of this article (e.g., Plantae|
|Plantae||Plants in a broad sense comprise the green plants listed above plus the red algae and the glaucophyte algae that store outside the plastids, in the cytoplasm. This clade includes all of the organisms that eons ago acquired their directly by engulfing (e.g., Plantae Cavalier-Smith, 1981|
|Plants in the widest sense refers to older, obsolete classifications that placed diverse algae, fungi or bacteria in Plantae .|
|Archaeplastida + cryptista|
The way in which the groups of green algae are combined and named varies considerably between authors.
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Boron Transporters In Gymnosperms
Gymnosperms are a group of nonflowering plants. There are studies which suggest the essentiality of B in these plants. However, a few research groups have worked on B transport in gymnosperms. For instance, in Pinus bankisiana, the seedlings were treated with excess B and it was seen that B accumulated in the needles, causing necrosis and also in roots. Further, it was observed that accumulation in needles was higher than in roots. Therefore, it can be predicted that some B exporter may be present in roots and shoots . In another study, B uptake mechanism was studied in Betula pendula, which is found in association with ectomycorrhiza Paxillus involutus . The B was reported to be taken up by the fungal partner by passive mechanism and was transported to the plant through its mycelium. Within the plant, the B was found to be translocated as B-mannitol association . This group of plants lacks the information and studies regarding the presence of B channels and B efflux transporters. The literature suggests the possibility of the presence of BOR transporters in gymnosperms, and thus it should be explored by various research groups.
Alok Sharma, … Santosh Kumar Upadhyay, in, 2021
Plant Body Of Gymnosperms
The plant body of gymnosperms is differentiated into well-defined roots, shoots and leaves. They are woody perennials which include medium-sized trees or tall trees and shrubs.
Fig: Some common gymnosperms
The main plant body of gymnosperms is a diploid sporophyte and is heterosporous in nature, that is, it produces two different types of spores – male microspores and female megaspores.
The spores are borne on chambers known as sporangia that are present on modified leaves known as sporophylls.
The haploid gametophytes are inconspicuous and depend on the sporophyte for nutrition and survival. The microspores develop into the male gametophyte known as pollen grain. The megaspore develops into a multicellular female gametophyte that bears two or more female sex organs or archegonia.
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Difference Between Angiosperms And Gymnosperms
Angiosperms and gymnosperms are the two main categories of the plants. Both are seed-bearing plants having few similarities. This is because of the fact that gymnosperms were present for more than 200 million years before the angiosperms evolved. The main difference between these two is their diversity. Angiosperms are more diverse in comparison to the gymnosperms. The higher diversity of angiosperms is due to their wide adaptability in terrestrial ecosystems. Angiosperms, are also known as flowering plants and having seeds enclosed within their fruit. Whereas gymnosperms have no flowers or fruits and have naked seeds on the surface of their leaves. Gymnosperm seeds are configured as the cones. Some other main characteristics which differentiate both are based on flowers, fruits, and seeds. In this article, we will deal with the detailed difference between Angiosperms and Gymnosperms in the tabular form for easy understanding.
Table of content
View Prepared Slides Of Gymnosperms
Figure 6.1: Young Zamia ovule.
Figure 6.2: Pine ovule
Figure 6.3: Pine young ovulate cone.
Figure 6.4: Pine staminate cone.
Figure 6.5: Pine pollen.
Figure 6.6: Pine needle.
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What Is The Evolutionary History Of Gymnosperms
The earliest group of gymnosperms are seed ferns called Pteridospermophyta, which are now extinct and are only known from fossil evidence .
These seed ferns bore seeds directly on their leaves or branches without being contained in specialized structures, like cones or fruits. Then, later in evolutionary history, the exposed ovules and cones characteristic of gymnosperms emerged.
For around 200 million years prior to the emergence of flowering plants, gymnosperms dominated the world. However, extreme climatic changes led to the extinction of many gymnosperm species. This accounts for the relatively low diversity among extant gymnosperm species.
Scientific And Cultural Uses
Basic biological research has often been done with plants. In , the breeding of pea plants allowed to derive the basic laws governing inheritance, and examination of in maize allowed to demonstrate their connection to inherited traits. The plant is used in laboratories as a to understand how control the growth and development of plant structures. predicts that space stations or space colonies will one day rely on plants for .
Ancient trees are revered and many are . themselves are an important method of dating in archeology, and serve as a record of past climates.
Plants figure prominently in , religion and . They are used as and state emblems, including and . Plants are often used as memorials, gifts and to mark special occasions such as births, deaths, weddings and holidays. The arrangement of flowers may be used to send hidden .
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Gymnosperms: Definition Examples And Reproduction
Gymnosperms which are also referred to as Acro Gymnospermae are a group of flowerless plants that produce seeds and cones. The term gymnosperm literally translates to “naked seed” as they are flowerless. This is due to the fact that gymnosperm seeds are not encapsulated within the ovaries. Instead, they are exposed on the surface of leaf-like structures where they sit and are called bracts. Gymnosperms are vascular plants belonging to Embryophyta which is a subkingdom and it includes a vast variety such as cycads, gnetophytes, conifers, and ginkgoes. There are other recognizable examples of these trees and shrubs which include spruces, pines, ginkgoes, and firs. These classes of gymnosperms are readily available in biomes such as temperate forests and boreal forests. The species thrive in moist or dry weather conditions. As mentioned earlier, gymnosperms do not contain the ability to produce any fruits or flowers, which is unlike angiosperms. According to biologists, gymnosperms are believed to be the very first vascular plants. They started to appear and inhabit the lands in the Triassic Period, which is estimated to be around 208-245 million years ago. The vascular system allows for the transportation of water throughout the plant which in turn made it possible for the colonization of gymnosperm land.
Gymnosperms: Classification And Main Orders
Let us learn about Gymnosperms. After reading this article you will learn about: 1. Classification of Gymnosperms 2. Main Orders of Modern Gymnosperms.
Classification of Gymnosperms:
It was generally accepted, and expressed in schemes of classification, that the Gymnospermae formed a group coordinated with the Angiospermae. From time to time suggestions have been made for splitting the Gymnospermae into a number of major groups taxonomically equivalent one to another and to the angiosperms.
Coulter and Chamberlain divided the gymnosperms into seven orders. Some of the orders are quite extinct and not found in present day.
These orders are as follows:
3. Cycadales-Mesozoic to present day
5. Ginkgoales-Palaeozoic to present day
6. Coniferales-Palaeozoic to present day
Chamberlain however, divided the gymnosperms into two large groups A. Cycadophyta and B. Coniferophyta.
In the Cycadophyta, sporophylls are in cones.
They include three orders:
The Coniferophyta is divided into four orders:
Ginkgoales-Palaeozoic to present day.
Coniferales-Palaeozoic to present day
Prof. B. Sahni divided the gymnosperms into two large groups and gave them theterms:
1. Phyllospermae and
They comprise of the Pteridosperms and the Cycadophyta . The seeds are being inserted on the modified leaves.
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