Tip Growth in Plant Cells Flashcards
How do most plant cells grow
Most plant cells grow across their entire surface through the coordinated actions of turgor pressure, cytoskeletal organization, and the cell secretory system
What determines the direction of plant cell expansion
The orientation of cellulose microfibrils in the cell wall, which is directed by the underlying cytoskeleton, particularly microtubules
What roles do turgor pressure and the secretory system play in cell growth
Turgor pressure provides the force for expansion, while the secretory system delivers cell wall materials to areas of growth
What is tip growth in plant cells
Tip growth is a form of highly polarised cell expansion, restricted to the apical tip of the cell, seen in pollen tubes and root hairs
How does tip growth differ from diffuse growth
Unlike diffuse growth (all-over expansion), tip growth is localised and faster, requiring tight regulation of cytoskeleton, vesicle delivery, and wall softening
What is the structure of a mature pollen grain
It contains a vegetative nucleus and either one generative cell or two sperm cells, depending on the species
What is the role of the vegetative nucleus in pollen
It regulates pollen tube growth and maintains cellular functions, but does not contribute DNA to the zygote
What happens to the generative cell during pollen tube growth
If only one generative cell is present, it divides mitotically during pollen tube growth to form two sperm cells
What is the function of the pollen tube
It transports male gametes (sperm) from the pollen grain to the egg within the ovule by growing through the pistil
How is the pollen tube initiated
Upon reaching the stigmatic surface, the pollen grain hydrates and germinates a tube from an aperture in the pollen wall
How does the pollen tube navigate through the pistil
It grows between cells of the transmitting tissue, guided by chemical and mechanical cues, toward the embryo sac
What happens when the pollen tube reaches the ovule
The tube bursts, releasing two sperm cells: one fertilises the egg, the other fuses with central cell nuclei to form the endosperm
What are colchicine and cytochalasin D used for in the experiment
Colchicine: inhibits microtubules
Cytochalasin D: inhibits microfilaments (actin)
What does DAPI stain and what is its purpose
DAPI binds to DNA, allowing visualisation of nuclei, such as the vegetative and generative/sperm nuclei in the pollen tube
What does aniline blue stain and what does it detect
Aniline blue stains callose, a β-1,3-glucan found in the walls of growing pollen tubes. detecting pollen tube growth
What would be the effect of cytochalasin D on pollen tube growth
Likely severe inhibition or cessation of tip growth due to blocked vesicle trafficking and impaired nucleus movement
What would be the effect of colchicine on pollen tube growth
Likely disruption in nuclear movement and orientation, with possibly milder effects on growth compared to actin inhibition
Why is tip growth considered a highly regulated process
Because it requires precise coordination of vesicle delivery, cytoskeleton dynamics, turgor control, and wall assembly to achieve rapid, directional growth
What experimental observations would indicate the involvement of the cytoskeleton in nucleus transport
Disrupted or delayed movement of vegetative or generative nuclei when either microtubules or microfilaments are inhibited
