Question

Which ability of gibberellins is used to increase the length of grape stalks? (a) Ability to increase apically (b) Ability to increase in length of axis (c) Ability to avoid apical dominance (d) All of these

Short answer

The correct answer is (d) All of these. Gibberellins can perform all the three mentioned functions that can help in increasing the length of grape stalks.

Step-by-step solution

Understanding terms

Firstly, each term needs to be understood accurately. Apical refers to the top or the highest point. So, an ability to increase apically means the ability of the plant to grow at the tip. Increasing in the length of axis refers to the elongation of main stem of the plant. Apical dominance is a phenomenon where the main central stem of the plant grows more strongly than the side stems. Thus, the ability to avoid apical dominance would mean that side stems are allowed to grow stronger instead of just the central stem.

Relating properties to characteristics of grape plants

Grapes grow on vines, with a long main stem and multiple side shoots carrying the fruit. Gibberellins have a role in stem elongation and also help in negating apical dominance, thereby promoting growth of side shoots.

Final Selection

On comparing the choices, we can see that gibberellins show all three abilities listed: they can help the plant to grow at the tip, they can elongate the main stem, and they can prevent apical dominance to promote side growth. Therefore, they could all be involved in increasing the length of grape stalks.

Key concepts

Stem Elongation

Stem elongation in plants is primarily influenced by plant hormones known as gibberellins. Gibberellins stimulate the elongation process by facilitating cell division and expansion in the inter-nodal regions of the stem. These inter-nodal areas are spaces between leaf nodes, and they are the central regions where growth occurs.

When gibberellins are applied to plants, they trigger cell walls to loosen, allowing cells to take in more water and nutrients, which in turn, helps the stem grow longer. This ability is particularly useful in agricultural practices, such as enhancing the growth of grape stalks for more extended and robust fruit-bearing vines.

• Gibberellins help in increasing plant height, which is a desirable trait for many fruits and crops.
• They are used to promote longer, slender plant structures, aiding in better light capture for photosynthesis.

Ultimately, stem elongation driven by gibberellins plays a vital role in a plant's ability to compete for sunlight and space in its environment.

Apical Dominance

Apical dominance is a phenomenon in plants where the central main stem grows more vigorously than the side stems or branches. This process is regulated by hormones, notably auxins that are produced in the apical or terminal bud of the plant. Apical dominance ensures that the plant focuses its resources on vertical growth rather than lateral growth.

However, gibberellins can disrupt apical dominance, enabling the side branches to grow alongside the main stem. This is particularly beneficial for plants such as grapevines, where robust side branch growth is desired.

• Breaking apical dominance allows plants to develop more branches and leaves, increasing their reproductive success.
• Gibberellins counteract the suppressive effects of auxins, promoting lateral growth.

In essence, by reducing apical dominance, gibberellins allow for a fuller and bushier plant overall, improving yield and quality of crops.

Plant Growth Hormones

Plant growth hormones are chemical signals that regulate various aspects of plant development, from seed germination to flower blooming. The main types include auxins, cytokinins, ethylene, abscisic acid, and gibberellins. Each hormone has unique functions but can also interact with others to regulate complex growth responses.

Gibberellins represent a crucial category of plant hormones, particularly known for:

• Promoting elongation of stems and leaves.
• Encouraging seed germination by breaking seed dormancy.
• Facilitating the transition from vegetative to flowering stages.
• Reducing apical dominance and encouraging lateral growth.

Through their applications, gibberellins greatly enhance agricultural productivity. Understanding and manipulating these growth hormones can lead to improved plant growth and increased crop yields, making them invaluable in modern agriculture.