ANALISIS DE FACTORES HISTÓRICO-CULTURALES Y SU INCIDENCIA SOBRE EL EMPODERAMIENTO SOCIAL
3.1 DE LA HISTORIA Y SU HERENCIA
3.2.10 La adulación hacia los poderosos
Characteristics of Flowering Plant - Differences between Gymnosperms and Angiosperms 87
3.3 Differences Between Gymnosperms And Angiosperms
Gymnosperms Angiosperms
- Do not have well developed flowers Have well developed flowers.
- Flowers lack calyx and corolla, they are called strobili Flower have perianth, calyx and corolla. No strobi
- Have naked seeds Have covered seeds
- All seeds have endosperms, no cotyledons Have both endospermous and cotyledonous seeds.
- Xylem tissues have tracheids only, no vessels Xylem tissues have vessels, no tracheids - They are terrestrial in habitat eg. whistling pine, cycas They are terrestrial but few are aquatic
- They have cones where naked seeds are formed. Seeds and fruits are produced after fertilisation
Fruits are not formed .
- The leaves are green in colour, small, scaly and Well developed true roots, stems and leaves
needle-like are present
- Seed endosperm is haploid Seed endosperm is triploid
- Phloem tissue has no companion cells Phloem tissue has companion cells
In tabular form, list six differences between Gymnosperms and Angiosperms 3.4 Advancement Of Flowering Plants Over Ferns
Flowering Plants Ferns
Plant body differentiated into distinct root and shoot system
Wscular bundles well developed comprising xylem and phloem.
Form pollen grains and pollen tubes that carry male gametes to the ovum.
Produce seeds with cotyledons or endosperms Have megasporangium that is protected by a coat at maturity
Have cambium that leads to secondary thickening
Plant body not divided into root and shoot system Nascular bundles less developed consists of tracheids
.
No pollen grains and pollen tube, male gametes consist of motile antherozoids
No seeds, have sori
Megasporangium absent, instead, archegonium present Cambium is absent, no secondary growth.
The possession of seeds, well developed vascular bundle, root, shoot and presence of cambium among
v. The seed of flowering plants is the new sporophyte and it depends on the parent plant vi. Seed plants are classified into Gymnosperms and Angiosperms
vii. Gymnosperms has naked seeds while Angiosperms have covered seeds
viii. Gymnosperms seeds has endosperms and no cotyledons while Angiosperms seeds have both endosperms and cotyledons.
1. In tabular form, list five reasons why flowering plants are more advanced than ferns.
(10 marks)
2. List five differences between Gymnosperms and Angiosperms (5 marks)
Idodo - Umeh (1996) College Biology
Sarojini T. Ramalingam (1993) Modern Biology.
0
Flowering Plants
1.0 2.0 3.0 3.1
.
3.2
Page
Introduction 90
Objectives 90
Dicotyledons and Monocotyledons 90
Morphology ofAngiospenns 92
Root System 92
3.1 Characteristics of Roots 1 93
3.4 Functions of Roots 93
3.5 Modification of Roots 94
3.5.1 Root Tubers 94
3.5:2 Climbing Roots 94
3.5.3 Breathing Roots 95
3.5.4 Prop Roots • 96
3.5.5 Stilt Roots 96
3.5.6 Buttress Roots 97
3.5.7 Epiphytic Roots 97
3.5.8 Sucking Roots 97 •
3.6 Internal Structure of the Root 98
4.0 Conclusion 99
5.0 Summary 99 .
6.0 Tutor MarkedAssignment 100
7.0 Further Reading and other Resources 100
•
89
In its earliest usage, when coined in 1960, the term
angiospermhad not its correct modern taxonomic significance. In 1827, Robert Brown gave it its present taxonomic distinction of meaning from gymnosperms, when he established the truly naked characters of the seeds of cycads and conifers. Even then, there was no plant classification which separated the gymnosperms from the angiosperms on this characteristics. This was because the life cycle of neither the cryptogams nor seed-bearing plants had the nature of a seed. When Hofineister correctly interpret( I the life history of Fern and in 1851 discovered the nature of the occurences in seed formation, he was able o see that the two series of events paralleled one another and to establish the significance of the origin and form of the seed as a criterion in classification. From that time gymnosperms were clearly separated from angiosperms, whereas they had previously been grouped together as dicotyledonous plants to distinguish them from the monocotyledonous plants. The term angiosperm now includes all the flowering plants other than gymnosperms and comprises therefore all the monocotyledonous as well as the dicotyledonous higher flowering plants.
In this text, we will discuss the differences between monocotyledonous and dicotyledonous plants, root system of angiosperms.
By the end of this unit, you should be able to;
i. list at least six differences between dicotyledonous and monocotyledonous plants list at least five characteristics of roots
iii list at least four functions of roots.
Do you remember that living organisms have features that are peculiar to them? Dicotyledons and monocotyledons do have theirs. The different features possessed by dicotyledonous and monocotyledonous plants.
Dicotyledons:
These are the more primitive angiosperms. They may be trees, shrubs or herbs. Most large trees with spreading branches are dicotyledons.
Dicotyledons have these features:
• They bear seeds which have two seed leaves or
cotyledonseach
• The vascular bundles of their stems and roots are arranged in a regular pattern
• They have a tap root system
• Dicotyledons usually undergo secondary growth; because of the presence of cambium cell.
Some examples of dicotyledons are
Hibiscus, Ipomea batatas(sweet potato),
Carica papaya(pawpaw),
Dioscorea sp.(yam), and
ligna unguiculata(cowpea).
* In dicotyledonous roots the number of xylem bundles varies from 2 to 6.
Monocotyledons:
These are the most advanced plants. They tend to be more emcient and specialised because they have fewer parts. As such they show a very high degree of adaptation to their environment.
They are generally herbs.
Monocotyledons
have these features:• Their floral parts - sepals, petals, pistils and stamens - exist in groups of four or five
• Their leaves have veins arranged in a branched network
Secondary growth
Yes No
Flowers
Parts in 4s or 5s
Leaves
Net-veined
network venation Roots
One main root (tap root system)
Vein parall
parallel
many main roots (11.4us, root system) roots are
pidermi vascular
Scattered vascular bundy Stem
Vascular
Root piliferous lay
Xylem (water phloem vascular Mud
conducting pith
xylem tissue) in
cortex
Large pith; ring of vascular tissues
Two
C
:cotyledo onet
Embryo
Differences Between Monocotyledons and Dicoodecons — Morphology ofAngiospenns — Roots System 91
* They bear seeds with one cotyledon each
* The vascular bundles of the stem are scattered
• Their floral parts exist in groups of three or multiples of three
* Their leaves have veins running parallel to one another
• They have a fibrous root system
* Monocotyledons do not undergo secondary growth because of the absence of cambium.
Some examples of monocotyledons are Zea mays (maize), Elaeis guineensis (oil palm), Axonopus compressus (carpet grass), Panicum maximum (Guinea grass) and Oryza sp. (rice).
* In monocotyledonous roots, the number of xylem bundles are numerous.
Table 2.1 Comparing Dicotyledons and Monocotyledons
DICOTYLEDON MONOCOTYLEDON
Note: All cereal plants are monocoOtledons
List at least five differences between Dicot and Monocot
branch root apical bud
flower bud
flower n de
l
internodc fruitn de cceds
leaf E
0
cc
axillary bud
main root AIR
SOIL •
O
ce
3.1 Morphology ofAngiosperms
It
will interest you to know the morphology of angiosperms.The dicot plant is made up of a single axis consisting of the root system (below the ground) and shoot system (above the ground) see fig. 2.1
Figure 2.1 Structure of a typical flowering plants.
3.2
Root System
The root system is the part of the plant growing in the soil. This excludes the underground stems which are
organs of perennation
(survival from year to year by vegetative means). There are two kinds of root systems, namely:tap root
andfibrous root system.
The root sysi: .n develops from radicle of embryo which normally stays below the ground, and because it never bears leaves or flowers is not divisible into nodes and internodes.Tap Root System:
This system is characteristic of the dicotyledonous plants. There is just one main root known as thetap root
growing deep down and giving rise to smaller branches, thelateral roots.
Tap roots are firm, if the primary radicle establishes itself to become a permanent and clearly defined organ, then together with its lateral branches it forms a tap root system and the primary radicle become the tap root.
Fibrous root systcm
stem fibrous root
lateral root
leaf
Differences Between Monocotyledons and Dicotylecons — Morphology o f Angiospenns — Roots System 93
The Fibrous Root System:
This is characteristic of monocotyledonous plants. In this system, there is a mass of roots arising from the base of the stem. The mass consists of several main roots of approximately the same size. These give off numerous branch roots which in turn give off other branch roots of smaller size. The roots are slender in appearance.
Figure 2.2. The Fibrous Root of Grass, Eleusine indica
Both the main and branch roots bear a root cap at their tips. The root cap protects the soft growing regions of the root tips. Here the cells are actively dividing to add new cells to the root.
Alittle above the root tips are some unicellular root hairs used for absorption of water and mineral salts from the soil into the plant body.
The root hairs are very numerous and tiny and should not be confused with the very small branch roots seen after an intact plant has been uprooted from the soil. One may need a microscope to observe the root hairs if they have not been damaged by uprooting . The root begins to thicken above the root hair region.
Root produced from parts other than the radicle of a seed are known
asadventitious roots.For example, the prop roots of maize which grow from the lower nodes of the stem into the soil. The roots seen in stem tubers, rhizomes, bulbs and corms are all adventitious roots.
3.3 Characteristics of Roots
The general characteristics of roots are as follows;
1. Roots grow inside the ground except for some modified aerial roots 2. Roots lack buds
3. Roots end in caps (stems end in buds)
4. Roots do not bear green pigments or chlorophyll
5. Roots possess unicellular hairs known as root hairs. (Hairs found in some stems and leaves are multicellular)
6. Nodes and intemodes are absent in roots.
3.4 Functions Of Roots
The main functions of roots are:
1. For absorption of water and dissolved mineral salts from the soil into the plant body through the root hairs.
2. For anchoring the whole plant firmly to the soil
3. Certain roots become modified to perform some special functions such as food storage, vegetative
reproduction, climbing, breathing in water
-logged soil and for extra support to the plant.
B.
swollen lateral oot
B. Cassava
adventitious root
Figure 2.3. Root Tuber Of (A) Carrot, (B) Cassava
leaf short stem
swollen tap root
lateral root
Root tuber of a car-rot
1. List at least six characteristics of roots 2. List four functions of roots
3.5 Modification of Roots
These will be summarised with reference to the particular function the modification serves. Both tap and fibrous roots may be modified for support, food storage or climbing.