XI Chap 15 Plant Growth Development Flashcards
Plant development is the sum of 2 processes: _______ and ________
growth and differentiation
The first step in plant growth is ____________
seed germination
_______ is regarded as one of the most fundamental and conspicuous characteristics of a living being
growth
Define growth
irreversible permanent increase in size of an organ / organ parts / individual cell
Growth is accompanied by _________ processes that occur at the expense of energy
metabolic (anabolic and catabolic)
Why is plant growth unique?
retain the capacity for unlimited growth throughout their life due to presence of meristems
Plant form of growth wherein new cells are always being added by activity of the meristem is called ___________
open form of growth
In ________________, the lateral meristems, vascular cambium and cork-cambium appear later in life.
dicotyledonous plants and gymnosperms
What are the meristems that cause increase in girth of organs?
lateral meristems, vascular cambium, cork-cambium
What is secondary growth of plant?
increase in girth of organs, later in life
Growth at cellular level is consequence of increase in amount of _________
cytoplasm
Increase in protoplasm is easy to measure directly. T or F?
False
Growth can be measured by increase in ? (6)
fresh weight, dry weight, length, area, volume, cell number
A single maize root apical meristem can give rise to _____ new cells per hour
17,500
Cells in watermelon may increase in size by upto ____________ times per hour
3,50,000
Growth of pollen tube is measured in terms of its ___________
length
What measure indicates growth in a dorsiventral leaf?
increase in surface area
Plant growth is divided into how many phases? What are they?
3
meristematic, elongation and maturation
The constantly dividing cells at the root and shoot apex represent the ________ phase of growth
meristematic
The cells in the meristematic region are rich in _______ and possess ______ nuclei
cytoplasm, large conspicuous
Describe cell walls of meristematic region cells
primary in nature,
thin,
cellulosic,
abundant plasmodesmatal connections
Cells next to the meristematic zone, away from the tip represent the phase of __________
elongation
What are characteristics of cells in elongation phase?
- increase vacuolation
- cell enlargement
- new cell wall deposition
Furthest away from the apex are the cells undergoing phase of __________
maturation
Cells of maturation zone attain their maximal size in terms of _____ and _______
wall thickening, protoplasmic modifications
What is growth rate?
increased growth per unit time,
What are the 2 types of growth rates?
arithmetic or geometrical
Arithmetic vs. geometric growth
Arithmetic - only one daughter cell of mitosis divides, other differentiates and matures; linear curve; Lt = L0 + rt
Geometric - both daughter cells continue to divide; starts with lag phase and eventually leads to a stationary phase due to limited nutrients; sigmoid/S-curve; W1 = W0 * e^rt
Relative growth rate is represented by the letter ____
r
Relative growth rate is the measure of the ability of the plant to ______
produce new plant material
Relative growth rate is aka ________
efficiency index
Final size of W1 depends on W0 wrt plant growth. T or F?
True
Quantitative comparisons between growth of living systems can be made in 2 ways:
absolute and relative
Plant cells grow in size by cell enlargement which in turn requires _______
water
_________ of cells helps in extension growth
Turgidity
Water also provides the medium for enzymatic activities needed for plant growth. T or F?
True
How do oxygen and nutrients help in plant growth?
Oxygen - releasing metabolic energy
Nutrients - synthesis of protoplasm and source of energy
Environmental signals such as light and gravity can affect plant growth. T or F?
True
Differentiation, dedifferentiation vs. redifferentiation
Differentiation - structural changes to cell wall and protoplasm
Dedifferentiation - cell that have lost ability to differentiate can regain it
Redifferentiation - dedifferentiated cells can once again lose the capacity to divide to perform other specific functions
To form a tracheary element, how do cells differentiate?
lose their protoplasm
develop strong, elastic, lignocellulosic secondary cell walls
Formation of meristems from fully differentiated parenchyma cells is an example of __________
dedifferentiation
Differentiation in plants, like growth, is open. T or F?
True, because cells/tissues arising out of meristem have different structures
Final structure at maturity of a cell/tissue is partly determined by the location of the cell within. T or F?
True
Cells positioned away from root apical meristems differentiate as __________ while those pushed to the periphery mature as _______
root-cap cells, epidermis
_________ includes all changes that an organism goes through during its life cycle from germination of the seed to senescence.
Development
Describe the sequence of developmental processes in plant cell/tissue/organ
meristematic cell
-> plasmatic growth -> differentiation
-> expansion/elongation -> maturation
=> mature cell -> senescence -> death
some cells in plasmatic growth phase divide again to join back meristematic cell
What is plasticity? Examples
ability of plants to follow different pathways in response to environment/phases of life to form different kinds of structures
e.g. heterophylly in cotton, corianer and larkspur
In __________ plant, different shapes of leaves in terrestrial vs aquatic habitats is an example of ____________ development
buttercup
heterophyllous
Plant growth regulators (PGR) are ______ molecules of _______ chemical composition
small, simple
diverse
Plant regulators could be?
indole compounds adenine derivative derivatives of carotenoids terpenes or gases
PGRs can be divided into 2 groups based on _______. The groups are?
functions;
promoters and inhibitors
Specify if these are promoters or inhibitors: auxins abscisic acid gibberellins cytokinins ethylene
auxins - promoter abscisic acid - inhibitor gibberellins - promoter cytokinins - promoter ethylene - can be either, mostly inhibitor
________ types of PGRs play an important role in plant responses to wounds and biotic/abiotic stresses.
Inhibitors
Pattern formation, seed formation and dormancy are growth promoting activities in plants. T or F?
False, first two are correct but dormancy is growth inhibiting
Discovery of each of the five PGRs were the result of years of concerted efforts of scientists across the world. T or F?
False, accidental discoveries
Charles Darwin and his son Francis Darwin observed that ____________ responded to unilateral illumination by growing towards the light source aka _____________
coleoptiles of canary grass, phototropism
______ of the coleoptile is the site of transmittable influence causing the bending of the plant.
Tip
Auxin was isolated by ____________ from tips of coleoptiles of _________
F. W. Went,
oat seedlings
The bakanae (foolish seedling) disease of rice seedlings was caused by _______ type of pathogen ___________ (scientific name)
fungal, Gibberella fujikuroi
_________ reported the symptoms of bakanae disease when treated with sterile filtrates of fungus Gibberella fujikuroi in the year ______
E. Kurosawa, 1926
The active substance in the pathogen causing bakanae is _________
gibberelic acid
___________ observed that from internodal segments of tobacco stems, the _______ proliferated only if in addition to auxins the nutrient medium was supplemented with one of the following:
F Skoog et al;
callus;
extracts of vascular tissues, yeast extract, coconut milk or DNA
___________ observed that from internodal segments of tobacco stems, the _______ proliferated only if in addition to auxins the nutrient medium was supplemented with one of the following:
F Skoog et al;
callus;
extracts of vascular tissues, yeast extract, coconut milk or DNA
In the year _____, ___________ identified the cytokinesis promoting active substance observed by F Skoog et al, and termed it __________
1965, Miller et al, kinetin
During mid-19__s, three independent researches reported purification and chemical characterisation of 3 inhibitors: ______
1960s;
inhibitor-B, abscission II and dormin
_____________ (3) are all chemically identical and are named abscisic acid (ABA)
Inhibitor-B, abscission II and dormin
In 1910, _________ confirmed release of volatile substance from ripened _______ that hastened the ripening of stored bananas. Later this substance was identified as ________
H. H. Cousins,
oranges,
ethylene
What are the five categories of PGRs?
- Auxins
- Gibberellins
- Cytokinins
- Ethylene
- Abscisic acid (ABA)
Auxins comes from Greek meaning _____
to grow
Auxin was first isolated from _________
human urine
The term auxin is applied to _______ acid and other compounds having growth regulating properties.
indole-3-acetic acid (IAA)
Auxins are generally produced by _______ in plants
growing apices of stem and roots
Auxins like ____ and ____ have been isolated from plants
Indole-3-acetic acid (IAA)
indole butyric acid (IBA)
_______ and _____ are synthetic auxins
Naphthalene acetic acid (NAA) and 2,4-dichlorophenoxyacetic (2,4-D)
Auxins help in what plant processes?
- initiate rooting in stem cuttings
- promote flowering (e.g. pineapple)
- prevent fruit and leaf drop at early stage
- promote abscission of older mature leaves and fruits
- induce parthenocarpy (e.g. tomatoes)
- controls xylem differentiation
- cell division
What is apical dominance?
The growing apical bud inhibits growth of lateral axillary buds
___________ usually results in the growth of lateral buds
Decapitation, removal of shoot tips
________ is used to prepare a weed-free lawn by gardeners
Auxin
Auxins are also widely used as herbicides. T or F?
True
2,4-D is widely used to kill _________ as it does not affect ___________
weeds, mature monocot plants
Gibberellins is a promotory or inhibitory PGR?
promotory
There are more than _________ gibberellins reported from ____ and _______
100, fungi, higher plants
_________ was one of the first gibberellins to be discovered and is the most intensively studied form.
GA3
All GAs are alkaline. T or F?
False, acidic
What roles do gibberellins play in plants?
- increase length of axis (e.g. grape stalks, sugarcane)
- cause fruits to elongate and improve shape (e.g. apple)
- delay senescence (fruits left longer on tree, extended market period)
- early seed production (by hastening the maturity period e.g. juvenile conifers)
- promotes bolting i.e. internode elongation prior to flowering (e.g. beet, cabbages and rosette plants)
In the brewing industry, GA3 is used to ________
speed up the malting process
Spraying sugarcane crop with ___________ can increase yield by as much as _______ per acre
gibberellins,
20 tonnes
Cytokinins were discovered as a kinetin (modified form of _____) from the _________
adenine, autoclaved herring sperm DNA
Kinetin is naturally occurring in fungi and higher plants. T or F?
False, does not occur naturally in plants
Search for natural substances with cytokinin-like activities led to isolation of _____ from _____
zeatin;
corn-kernels and coconut milk
Natural cytokinins are synthesised in regions where ___________
rapid cell division occurs
Cytokinins help plants in what ways?
- produce new leaves
- produce chloroplasts in leaves
- lateral shoot growth
- adventitious shoot formation
- overcome apical dominance
- nutrient mobilisation => delay of leaf senescence
__________ is a gaseous PGR
Ethylene
Ethylene is synthesised in large amounts by _______
tissues undergoing senescence and ripening fruits
Influence of ethylene on plants?
- horizontal growth of seedlings
- swelling of axis
- apical hook formation in dicot seedlings
- senescence and abscission of plant organs (esp. leaves and flowers)
- fruit ripening (enhances respiration rate)
- flowering and synchronising fruit-set (pineapples and mango)
- breaks seed and bud dormancy i.e. initiates germination (e.g. peanut seeds, potato tubers)
- rapid internode/petiole elongation (e.g. deep water rice plants)
- helps leaves / upper shoot to reman above water
- promote root growth and root hair formation => increased SA for absorption
___________ is one of the most widely used PGRs and ____ is the most widely used source of it.
ethylene, ethephon
Ethephon in an aqueous solution is readily absorbed and transported within the plants and releases ethylene rapidly. T or F?
False, releases slowly, everything else is correct.
Ethephon effects on plants?
- fruit ripening in tomatoes / apples
- abscission in flower and fruits (cotton, cherry, walnut - thinning)
- female flowers in cucumber => higher yield
____________ was discovered for its role in regulating abscission and dormancy
Abscisic acid - ABA
Effects of ABA on plants:
- general plant growth inhibitor
- inhibits metabolism
- inhibits seed germination
- stimulates closure of stomata
- increases tolerance to stresses
- withstand seed desiccation
What is respiratory climactic?
rise in rate of respiration during ripening of fruits as a result of ethylene
________ PGR is also called the stress hormone
ABA
In most situations, ABAs act as an antagonist to ____________
GAs
______ PGR plays an important role in seed development, maturation and dormancy.
ABA
PGR roles could be complimentary or __________, individualistic or ___________
antagonistic, synergistic
The role of PGR is of only one kind of intrinsic control. T or F?
True
Many extrinsic factors control plant growth and development via PGRs during events like vernalisation or plant movements. T or F?
True
Long day, short day vs. day neutral plants?
LD - for a period exceeding a critical duration
SD - for a period less than critical duration
Day-neutral - no correlation between light exposure duration and flowering response
What is photoperiodism?
response of plants to periods of day and night
Not only duration of light but also duration of dark is of equal importance to plant growth. T or F?
True
Shoot apices (the precursor to flowering apices) can perceive photoperiods just like flowering apices. T or F?
False, they cannot
It has been experimentally shown that a hormonal substance is responsible for flowering; it migrates from leaves to shoot apices to induce flowering after exposure to necessary photoperiod. T or F?
False, it’s a hypothesis (not proven) but described accurately
What is vernalisation?
When plant flowering is quantitatively or qualitatively dependent on exposure to low temperature
What is the function of vernalisation?
- prevents precocious reproductive development late into growing season
- enables plant to have sufficient time to reach maturity
What are the 2 varieties related to vernalisation?
Winter - planted in autumn, germinate, small seedlings in winter, resume growth in spring, harvested around mid-summer
spring - planted in spring, flower and produce grain by summer
Some examples of food plants that have winter and spring varieties?
wheat, barley, rye
What are biennial plants?
biennial = monocarpic plants that normally flower and die in second season
Examples of biennial plants?
Sugarbeet, cabbages and carrots
How is vernalisation seen in biennial plants?
subjecting growth to a cold treatment => subsequent photoperiodic flowering response
What happens in a seed which fails to germinate even when external conditions are favourable?
period of dormancy under endogenous control (not controlled by external factors)
What are some reasons for seed dormancy?
- impermeable and hard seed coat
- presence of chemical inhibitors (e.g. ABA, phenolic acids, para-ascorbic acid)
- immature embryos
Seed dormancy can be overcome through natural and man-made measures. T or F?
True
Root and shoot apical meristems sometimes along with __________ contribute to the elongation growth of plant axes.
Intercalary meristem
General principles for differentiation for cell, tissues and organs are similar. T or F?
True
Intercellular intrinsic factors are the chemical substances called PGRs. T or F?
True
Any PGR has diverse physiological effects on plants. T or F?
True
Diverse PGRs manifest uniquely different effects. T or F?
False, can be similar effects
