35 Plant Structure, Growth and Development Flashcards
What is a tissue?
A group of cells consisting of one or more type of cell.
What are the main systems of a plant?
The shoot system and the root system.
What is the major terminology that describes the shoot system?
The main shoot is called the stem. It has ‘vegetative shoots’ that grow of. They are joined to the stem by ’nodes’. The region between the nodes is called the ‘internode’
At the top of the stem and at the end of each vegetative shoot is an ‘apical bud’. (end of vegetative shoot may be leaf) Along the stem there may be ‘auxillary buds’
Besides ‘vegetative shoots’, ‘reproductive shoots’ also branch of from the stem and terminate in flowers.
What are the two most basic patterns of root systems?
’Taproot systems’ and ‘’fibrous root systems’
Describe a ’taproot system’?
A single vertical ’tap root’ is a thick root that is an extension of the stem.
Along its length ‘lateral (branch roots)’ branch of it more-or-less horizontally.
Describe a ‘fibrous root system’
A mat of thin roots spread out under the soil.
How do ’taproots’ and ‘fibrous roots systems’ differ in their adaption to specific climates?
Fibrous roots systems do not usually penetrated as far and are thus best adapted to shallow soils or regions where rainfall is light do does not moisten the soil far below ground level.
Tap roots often anchor the plant better. The fibrous roots are could at holding the topsoil in place hence why grasses prevent erosion.
In what plants are taproots typically seen?
Most eudicots and gymnosperms
In what plants are fibrous roots systems typically seen?
Monocots such as grasses.
What adaptation is found on many roots to increase the rate at which they can absorb nutrients?
Fine projections called ‘root hairs’
What are some specific forms of roots with evolutionary advantages?
Prop roots, storage roots, ’Strangling aerial roots’ buttress roots and pneumatophores
What are prop roots?
Roots that extend from the lower trunk of a tree.
This helps support the tree such as the Hala trees that live in unstable sand soils in the South Pacific.
What are storage roots?
Roots that can store water and nutrients underground, often by swelling.
These include potatoes.
What are ’Strangling’ aerial roots?
The seeds of these species germinate in the branches of tall trees of other species and send many aerial roots to the ground. These snakelike roots gradually wrap around the host tree and kill it by blocking its light
What are buttress roots?
Like prop roots they extend from the trunk although buttress roots often start lower.
Unlike prop roots which a are normal sticks the area under the ‘buttress root’ is filled so that they are ◢
What are ‘penumatophores’?
Roots that stick out of the ground i.e. the ones mangroves have.
They are important for roots to obtain oxygen which is lacking the thick, waterlogged roots.
What types of roots do mangroves have?
‘Pneumatophores’
What does ’node’ refer to on a plant?
Where the leaf joins the stem
What does ‘internode’ refer to on a platns?
The stem segment between nodes.
What are the shoots that branch of the plant called?
Lateral shoots or more often ‘branches’
What is a bud composed of?
Developing leaves and a compact series of nodes and internodes
What is found at the top of the stem and of each lateral shoot?
Apical buds aka ’terminal buds’
What are buds on the sides of the stem called?
Auxillary buds.
What determines which bud develops?
Generally speaking the growth is concentrated at the ‘apical bud’ as it exerts ‘apical dominance’ that suppresses the growth of the auxiliary buds.
If the apical bud becomes shaded its will lessen this suppression. This allows the auxiliary buds to develop into a ’lateral shoot’ (branch) to allow the plant to get light.
What are the basic structures plants have to perform asexual reproduction?
Rhizomes, bulbs, stolons and tubers.
What asexual reproduction structure is a root?
None: they are all technically stems event if they are underground.
What are ‘rhizomes’?
An underground asexual structure that consist of a shoot that grows just under the soil surface.
Along the rhizomes are auxiliary buds that can develop into vertical stems and thus new plants.
What are ‘bulbs’?
Vertical underground shoots that consist of the enlarged bases of leaves that store food.
The individual leaves, called ’storage leaves’ explain the many layers of an onion: each layer is a leaf.
What are stolons?
Horizontal shoots that grow along the surface.
They allow asexual reproduction as ‘plant lets’ form at nodes along each ‘runner’ (stolon)
What are tubers?
Enlarged ends of rhizomes or stolons that are specialised for storing food in the form of starch.
What is the basic structure of a leaf?
It is connected to a ‘node’ by a ‘petiole’.
The actual leaf may con of a ‘main rib’ (eudicot only?) and a series of smaller veins to transport nutrients to and from the leaf cells.
The actual leaf blade is called the lamina?
How does leaf structure differs between plant species?
In Monocots there are typically veins that pun in parallel from the petiole. for example the flax leaves
In Eudicot leaves there is typically a ’net like web’ of veins.
What are the fundamental ways in which leaves are structured ?
Simple leaf, compound leaf and ‘doubly compound leaaves’
What are ’simple leaves’?
When the leaf has a simple undivided lamina and is to only one that extends from the petiole.
What compound leaves?
In a compound leaf, the blade consists of multiple leaflets. A leaflet has no axillary bud at its base.
Each leaflet connects to the petiole not the stem.
What are double compound leaves?
Each leaflet is divided into smaller leaflets.
Therefore ‘compound leaves’ branch of from the petiole.
What are some advantages to compound leaves?
Since each leaflet is smaller than a normal leaf this prevents it from catching in the wind and falling off easily.
Pathogens might only infect one small leaflet, not the entire leaf.
What are some special adaptions of leaves?
Tendrils, Spines, Storage leaves, reproductive leaves and Bracts.
What are tendrils?
Modified leaves that that cling onto neighbouring plants etc. and thus support the plant.
(note that tendrils are often leaves but can be stems in some species)
What are spines?
The spines of cacti are actually leaves; photosynthesis is carried out by the fleshy green stems which constitute to main body of the cactus.
What are storage leaves?
Swollen leaves that many succulents have to store water
What are reproductive leaves?
Leaves that aid in asexual reproduction.
For example Kalanchoë daigremontiana, produce adventitious plantlets, which fall off the leaf and take root in the soil.
What does ‘adventitious’ refer to?
A plant organ that grows in an unusual location, such as roots arising from stems or leaves.
What is the word that means growing from an unusual place i.e. roots from the stem?
‘Adventitious’
What are the basic types of plant tissue?
Dermal tissue, ground tissue and vascular tissue.
What is the ‘dermal tissue’?
The outer layer of the plant that acts as its protective coating.
What are some examples of dermal tissue?
In nonwoody plants there is tissue called the epidermis (tightly packed cells). In woody plants, protective tissues called periderm replace the epidermis in older regions of stems and roots.
In leaves and most stems, the cuticle (waxy coating on epidermis surface) helps prevent water loss.
What is an example of a specialised structure pro ducted by some plants on the dermal tissue?
Trichomes
What are trichomes and what advantage do they offer?
Hairlike outgrowths of the shoot epidermis.
In some desert species, they reduce water loss and reflect excess light,
However their primary function is to provide defense against insects by forming a barrier or by secreting sticky fluids or toxic compounds.
For instance, the trichomes on aromatic leaves such as mint secrete oils that protect the plants from herbivores and disease.
What is the purpose of the vascular tissue system?
To carry nutrients throughout the plant.
What are the main components of the vascular tissue system?
Xylem and Phloem
What is the vascular system of a root or stem collectively called?
Its ’stele’
What does ’stele’ refer to?
The collective vascular system of a root or stem.
How does the arrangement of the ’stele’ vary between plants and regions?
In angiosperms the root stele is a solid central vascular cylinder of xylem and phloem. T
he stele of stems and leaves consists of vascular bundles, separate strands containing xylem and phloem.
What does the ground tissue system consist of?
Pretty much anything that isn’t vascular or dermal.
It is divided into ‘pith’ and ‘cortex’
What is the difference between ‘pith’ and ‘cortex’ in the ground tissue system?
Ground tissue that is internal to the vascular tissue is known as pith, and ground tissue that is external to the vascular tissue is called cortex.
What is the function of the ground tissue?
It is not just a filler and thus is involved in storage, photosynthesis and support of the plant.
What are the basic types of plant cells?
Parenchyma, Collenchyma and Sclerenchyma.
What is the structure of parenchyma cells?
They have thin and flexible primary cell walls with most lacking secondary cell walls.
They typically have a large central vacuole.
Most parenchyma cells retain the ability to divide and differentiate into different plant cell types i.e. for wound repair
What functions do parenchyma cells perform?
They perform most of the metabolic functions of the plant, synthesizing and storing various organic products
For example photosynthesis occurs within the chloroplasts of parenchyma cells. Some parenchyma cells in stems and roots have colourless plastids that store starch.
Therefore parenchyma a cells are typically alive when mature
What is the fleshy tissue of most fruits mad up of?
Parenchyma cells
What is the structure of collenchyma cells?
They are elongated cells that are often found in stands. They have thicker primary cells walls than parenchyma cells but the walls are unevenly thickened.
What is the purpose of collenchyma cells?
Young stems and petioles have strands of collenchyma cells below their epidermis. to support theses structures. They are flexible so don’t restrain growth.
At maturity, these cells are living and flexible, elongating with the stems and leaves they support
What is the structure of sclerenchyma cells?
They are more rigid than collenchyma as they have thick secondary cell walls with large amounts of lignin.
Sclerenchyma cells are divided into two types: sclereids and fibres
In what organisms are sclerenchyma cells found?
All vascular plants but no bryophytes.
What is the function of sclerenchyma cells?
They can not elongate and thus support regions of the plant that have stopped growing. For example they make up a large component of wood.
Since their main function is to support the cell most produce thick secondary cell walls and then die as they mature, leaving behind a skeleton.
What are the basic types of sclerenchyma cell?
Sclereids and fibres.
How do ’sclereids’ and ‘fibres differ’
Both are forms of sclerenchyma and thus have thick lignified secondary cell walls as they function in support.
Sclereids, are boxier than fibers and irregular in shape, have very thick, lignified secondary walls.
Fibers, are usually grouped in strands and are long, slender, and tapered.
Where are sclereids found?
They are what make nutshells and seed coats hard and give pears their gritty texture.
Where are fibres (sclerenchyma) found?
They are uses for making ropes. Flax fibres are used for weaving into linen.
What is xylem composed of?
Two different types of ‘water-conducting cells’: tracheids and vessel elements.
In what plants are tracheids found in xylem?
Almost all vascular plants
In what plants are vessel elements found in xylem?
Most angiosperms, a few gymnosperms and some seedless vascular plants.
What is the structure of tracheids?
They are long, thin cells with tapered ends.
Water moves from cell to cell through ‘pits’ which are regions where the the secondary cell wall is missing and thus water has to pass only through the primary cell wall.
What is the structure of vessel elements?
Vessel elements are generally wider, shorter, thinner walled, and less tapered than the tracheids.
They are aligned end to end in a stack, forming long micropipes known as vessels.
The end walls of vessel elements have ‘perforation plates’ (the walls have lots of holes) so enable water to flow freely through the vessels.
What prevents the tracheids and vessel elements from collapsing?
They are hardened with lignin which not only prevents them from collapsing but also supports the platen.
What type of structure are the stalks of celery?
Petioles as they support the leaves.
What makes up the ’strings’ of celery?
Collenchyma cells.
Besides tracheids and ‘xylem vessels’, what structures are found in xylem?
Xylem fibres and Xylem parenchyma.
What are xylem vessels also known as?
Xylem Tracheae
What are xylem fibres?
Dead sclerenchyma fibres that found between the vessels and the tracheids that provide mechanical support.
What are xylem parenchyma?
This is the only living component in the xylem tissue and consists of parenchyma cells.
They store reserves of food.
What is xylem divided into?
Primary xylem and secondary xylem
Primary xylem is further divided into protoxylem and metaxylem
How do protoxylem and metaxylem differ?
When xylem first forms it starts as protoxylem then develops into metaxylem and eventually secondary xylem.
Protoxylem has a narrower lumen. Protoxylem undergoes ‘annular and spiral thickening’ whereas metaxylem undergoes ’sclariform, reticulate and pitted thickening’
What is phloem composed of?
Two types of ‘water conducting cells:’ Sieve tubes or sieve cells
How does the structure of phloem differ between plants?
Seedless vascular plants and gymnosperms have phloem with ’sieve cells’
Angiosperms have ’sieve tubes’ which are composed of chains of cels called ’sieve tubes elements’ (aka sieve tube members)
