Problem 126 - Objective Biology for NEET

Question

Assertion: Plant shows open growth. Reason: Plant contains meristmetic tissues.

Step-by-Step Solution

Answer

Both the assertion and the reason are correct, and the reason is the correct explanation for the assertion.

Step 1: Understanding Concepts

Meristematic tissues in plants are responsible for plant growth. 'Open growth' refers to the ability of plants to continually produce new leaves, stems, and roots during their lifetime.

Step 2: Connecting Concepts

Meristematic tissues can differentiate into all types of plant tissues. Their continuous division allows the plant to exhibit open growth, that is, to continuously produce new organs.

Step 3: Drawing Conclusion

Therefore, the assertion is correct that a plant shows open growth, and the reason is also correct, which states that a plant contains meristematic tissues that contribute to this open growth.

Key Concepts

Open Growth in Plants

Open growth in plants refers to their remarkable ability to grow throughout their lifespan. Unlike animals, many plants do not have a predetermined size or shape; they can continue to expand and produce new structures as long as they live. This perpetual growth occurs thanks to specialized tissues known as meristematic tissues.

What makes meristematic tissue unique is its possession of undifferentiated cells – akin to stem cells in animals – which divide and contribute to the formation of various plant organs such as leaves, stems, roots, and flowers. The process is akin to adding new building blocks to the structure of a plant over time. This characteristic is vital for plant adaptation and survival, as it allows plants to replace damaged parts, grow towards light sources, or spread roots in search of nutrients and water.

Another fascinating aspect of open growth in plants is the presence of apical meristems. These are located at the tips of roots and shoots and are key players in lengthening these parts, enabling a plant to push its boundaries into new spaces and explore different environmental niches.

Plant Growth

Plant growth involves both an increase in size and an increase in the number of cells, which occur through cell division and enlargement. Understanding how plants grow involves delving into the various stages of the plant lifecycle, from a dormant seed to a fully mature plant that undergoes flowering and fruiting.

Three primary factors contribute to plant growth: genetic factors, environmental influences, and the availability of nutrients. Genetically, plants have predetermined patterns of growth that dictate the arrangement of leaves and the shape of the plant. But it is the environmental factors such as light, water, temperature, and soil quality that heavily impact how well a plant can express its genetic potential.

Moreover, plants exhibit different types of growth. Primary growth allows a plant to extend its roots and shoots, giving it increased access to above and below ground resources. Secondary growth, on the other hand, results in increased girth of the plant, particularly noticeable in the thickening of tree trunks.

Differentiation of Plant Tissues

Differentiation of plant tissues is a pivotal process where previously undifferentiated cells of the meristematic tissues become specialized in structure and function to form distinct types of plant tissues. This occurs once the plant cells have ceased division and begin changing to fulfill specific roles.

Key types of differentiated tissues include dermal tissue for protection, vascular tissue for transport, and ground tissue for metabolism and support. The specialization of these cells leads to the creation of organs such as leaves for photosynthesis, stems for support and transport, roots for nutrient and water absorption, and reproductive structures like flowers and fruits.

Phrase differentiation evokes the idea of cells taking on a new identity, much like students choosing different career paths after graduation. This is essential for plants as it brings about the organization within the plant body and allows for efficient functioning of the plant's biological systems. As cells differentiate, they contribute to the plant's overall growth and ability to respond dynamically to environmental challenges.