Module: | Embryo, Seed, Fruit & Apomixis
Q95: Consider the following statements regarding the in vitro chemical gradients required for pollen tube growth:
1. Successful pollen tube germination and sustained growth in an artificial medium heavily rely on the presence of sucrose, boron, and calcium.
2. Intracellularly, a steep, tip-focused calcium ion gradient directly orchestrates the continuous fusion of Golgi vesicles at the growing apex.
3. Potassium ions are the primary biological polymers secreted by these vesicles to construct the rigid outer wall of the mature pollen tube.
Which of the above statements is/are correct?
2. Intracellularly, a steep, tip-focused calcium ion gradient directly orchestrates the continuous fusion of Golgi vesicles at the growing apex.
3. Potassium ions are the primary biological polymers secreted by these vesicles to construct the rigid outer wall of the mature pollen tube.
Which of the above statements is/are correct?
✅ Correct Answer: A
The correct option is A. Statements 1 and 2 are correct, whereas Statement 3 is a structural falsehood.
To study pollen physiology in vitro (e.g., in a hanging drop slide), botanists must simulate the stigmatic environment.
The nutrient broth requires sucrose (for osmotic balance and energy metabolism) and the trace elements boron and calcium.
Causally, within the extremely rapid-growing pollen tube, calcium ions (Ca2+) form an intense concentration gradient perfectly localized at the extreme tip.
This calcium spike acts as the molecular trigger, commanding millions of secretory vesicles to fuse with the apical plasma membrane, thereby driving forward elongation.
Statement 3 is completely incorrect.
Potassium is an ion, not a polymer.
The vesicles guided by the calcium gradient actually secrete complex polysaccharides, specifically pectin and cellulose precursors, which are essential for building the physical cell wall of the extending tube.
To study pollen physiology in vitro (e.g., in a hanging drop slide), botanists must simulate the stigmatic environment.
The nutrient broth requires sucrose (for osmotic balance and energy metabolism) and the trace elements boron and calcium.
Causally, within the extremely rapid-growing pollen tube, calcium ions (Ca2+) form an intense concentration gradient perfectly localized at the extreme tip.
This calcium spike acts as the molecular trigger, commanding millions of secretory vesicles to fuse with the apical plasma membrane, thereby driving forward elongation.
Statement 3 is completely incorrect.
Potassium is an ion, not a polymer.
The vesicles guided by the calcium gradient actually secrete complex polysaccharides, specifically pectin and cellulose precursors, which are essential for building the physical cell wall of the extending tube.