Question

Select the correct statement from the following: (a) Mineral nutrients taken up by the roots and transported upward into stem, leaves and growing region. (b) When a plant part undergoes senescence, the nutrient always remain in the senescence part and gets lost from the plant. (c) In flowering plant the complex traffic of compound in unorderly manner moving in different direction. (d) All hormones shows polarised movement.

Short answer

Statement A, which states 'Mineral nutrients taken up by the roots and transported upward into stem, leaves, and growing region.' is correct as it correctly describes the process of nutrient transportation in plants.

Step-by-step solution

Analysis of Statement A

Statement A suggests that mineral nutrients are absorbed by the roots of plants and transported upwards to the stem, leaves, and growing areas. This statement is consistent with the understanding of how mineral nutrients are absorbed and distributed in plants. The process of nutrient transportation in plants is primarily upward from roots to different parts of the plant.

Analysis of Statement B

It's mentioned that during plant senescence, nutrients remain in the senescent part and are lost from the plant. But this is incorrect, as during plant senescence, a plant reabsorbs valuable nutrients from its leaves and recycles them to the younger parts before they fall off.

Analysis of Statement C

Statement C implies that the flow of compounds in flowering plants is chaotic or unorderly. However, this is incorrect. The movement of compounds in plants follows a specific order, generally from the site of synthesis to the site of utilisation or storage through the vascular system.

Analysis of Statement D

Statement D states that all hormones show polarised movement. Nonetheless, not all hormones in plants do so. Auxin is a hormone which shows polar movement but other hormones don't necessarily have a polarised direction of movement.

Key concepts

Mineral Nutrient Transport

Plants are remarkable organisms that perform complex transport functions essential for their growth and survival. Mineral nutrient transport occurs mainly from the roots to the above-ground parts of the plant, such as the stem and leaves. This process is commonly driven through the vascular system, consisting of the xylem and phloem.

• Xylem: This tissue primarily conducts water and dissolved minerals from the roots upwards to the rest of the plant through a process known as transpiration. Water evaporates from the leaves, creating a negative pressure that pulls the water column upward.
• Phloem: Unlike xylem, phloem can transport nutrients in multiple directions, depending on the plant's needs. It is responsible for the distribution of sugars and other metabolic products from sources like leaves to sinks such as roots and fruits.

Nutrient transport is crucial for various plant functions, including photosynthesis, respiration, and growth. The effective movement of nutrients ensures that all parts of the plant receive the resources they need to thrive.

Senescence in Plants

Senescence is a natural part of a plant's lifecycle where there is a gradual aging process of a plant or its organs. While it might seem like a plant is wasting away during senescence, it's actually an opportunity for resource conservation and redistribution. During senescence, plants actively recycle nutrients from the older, senescing parts to younger growing areas. Essential elements such as nitrogen and phosphorus are reabsorbed from the leaves before they are shed. This efficient recycling mechanism allows the plant to retain valuable nutrients that would otherwise be lost. The process of senescence is regulated by a balance of plant hormones, including ethylene and abscisic acid, which signal the plant to start reabsorbing nutrients and prepare for tissue breakdown. Consequently, senescence is not just decay but a highly regulated, strategic phase for nutrient conservation.

Movement of Plant Hormones

Plant hormones, also known as phytohormones, play essential roles in regulating a plant's growth, development, and responses to environmental stimuli. Hormones like auxins, gibberellins, cytokinins, ethylene, and abscisic acid are pivotal in these processes, and each hormone has its unique movement patterns within the plant.

• Polar movement: Auxin is a well-known hormone exhibiting polar transport. It moves in a single direction from the tip of shoots and roots towards the base, significantly influencing growth patterns.
• Non-polar movement: Other hormones, such as cytokinin and gibberellins, do not exhibit strict directional movement. They can move to various parts of the plant as needed for processes like cell division and elongation.

The movement and interaction of these hormones are crucial for coordinating developmental processes, allowing plants to adapt to changes in their environment effectively.

Nutrient Recycling in Plants

Plants have evolved sophisticated systems to recycle nutrients, ensuring optimal utilization and minimizing waste. Nutrient recycling is a vital process that allows plants to adapt to nutrient-poor conditions and seasonal changes. Key elements like nitrogen, phosphorus, and potassium are often recycled from older leaves and tissues to new growth areas. This recycling supports critical functions such as new leaf development and root growth. By breaking down complex organic compounds in older tissues, plants remobilize these nutrients through processes involving enzymes. This recycling process is essential, especially during stress conditions or in nutrient-poor soils. It ensures that the plant conserves its resources and maintains healthy growth even when external nutrient sources are scarce. By continuously cycling nutrients, plants play a crucial role in maintaining ecosystem stability and productivity.