Plant Physiology

Chapter Overview

Plant Physiology provides an exhaustive exploration of the vital physiological mechanisms enabling tracheophytes to thrive, nourish, transport solutes, and respond to their environment. The chapter starts with plant nutrition, distinguishing between essential macronutrients and micronutrients, detailing deficiency symptoms, and examining carnivorous adaptations in insectivorous plants like Pitcher Plant, Sundew, and Venus Flytrap living in nitrogen-deficient bogs.

It thoroughly analyzes internal transport and gas exchange dynamics. Students explore stomatal opening and closing driven by the starch-sugar interconversion hypothesis and proton-potassium ion influx mechanisms, mechanical support provided by parenchyma, collenchyma, and lignified sclerenchyma fibers, and water potential components (solute and pressure potential). Transport of water and minerals is illuminated through root uptake pathways (apoplast, symplast, vacuolar) and the cohesion-tension theory of sap ascent in xylem vessels, coupled with Ernst Münch's pressure-flow hypothesis for source-to-sink sucrose translocation in phloem sieve tubes.

The concluding units explore plant growth, regulation, and environmental adaptation. The chapter reviews apical, lateral, and intercalary meristems, details primary versus secondary growth, and analyzes major plant growth regulators (auxins, gibberellins, cytokinins, abscisic acid, and ethylene). Additionally, it evaluates osmoregulatory adaptations across hydrophytes, mesophytes, xerophytes, and halophytes, thermoregulation, tropic and nastic plant movements, phytochrome-mediated photoperiodism (short-day, long-day, and day-neutral plants), and the chilling induction of vernalisation.