Plant Transport and Physiology

Cholodny-Went Theory explains phototropism (bending toward light) through unequal auxin distribution - more auxin accumulates on the shaded side causing cells to elongate more. Photomorphogenesis is light-mediated development, photoperiodism is response to day length, and photorespiration is a wasteful process in C3 plants.

Little leaf disease is a physiological disorder caused by zinc deficiency, where new leaves are extremely small and chlorotic. Zinc is essential for the synthesis of auxin (IAA), and its deficiency leads to stunted growth with characteristic small leaves. Copper, boron, and iron deficiencies cause different symptoms like wilting, corky lesions, or interveinal chlorosis respectively.

Walls that form small bundles of durable layers of tissue in most plants is called sclereid.

Boron deficiency leads to the loss of geotropic response.

Symptoms of sulphur deficiency include yellowing of leaves and stunted growth.

RNA interference is an important innate defence against viruses.

When all tissues except xylem are removed, the root will die first. This is because roots depend on energy (ATP) from photosynthesis occurring in leaves, which requires phloem for sugar transport. Without phloem, roots cannot receive the organic nutrients needed to sustain cellular respiration and growth. Leaves and stem may survive temporarily on stored nutrients, but roots are most distant from these reserves.

The increase in respiration rate during fruit ripening in climacteric fruits like bananas is called the climacteric (or climacteric rise). This burst of respiration (with ethylene production) marks the transition to ripening. Anthesis is flower opening, climax is an ecological term, and photorespiration is a light-dependent process in plants that consumes oxygen and releases CO2.

The movement of water and minerals in a plant involves passage through a root, then in the xylem (especially the vessels) and finally through the leaves.

When the plant is an embryo, vascular tissue emerges from procambium tissue.

Water moves up through xylem vessels and tracheids during ascent of sap - a process driven by transpiration pull, root pressure, and capillary action. Cambium is meristematic tissue, phloem transports food, and endodermis is a root cortex layer.

While plants require oxygen for cellular respiration, this process occurs continuously and oxygen is readily available from the atmosphere. Photosynthesis depends on carbon dioxide concentration, which is typically the limiting factor in plant growth. Nitrogen is obtained through soil, but plants don't directly use atmospheric nitrogen in significant quantities. Sulphur dioxide is not essential for plant life. Plant productivity is primarily limited by CO2 availability for photosynthesis.

Stomata are microscopic pores found primarily on leaf surfaces. They are often referred to as stomas or fine pores in botany. Lenticels are raised pores on stems for gas exchange, hydathodes secrete water, and bark is protective tissue.

Capillary water is the water held in soil pores against gravity by surface tension, and it is the main source of water available to plant roots. Gravitational water drains away quickly, hygroscopic water is tightly bound to soil particles, and chemically bound water is unavailable to plants.

Many grass species roll or curl their leaves during drought to reduce surface area exposed to sun and wind, minimizing water loss through transpiration. Hibiscus, lotus, and ferns do not exhibit this specific drought adaptation. Grasses have evolved specialized structures for this response.