Plant Physio Exam Sources

(Lee and Lopez-Molina, 2012)

“Control of seed germination in the shade”; explores how seeds detect and respond to shade through phytochromes that sense a low red-to-far-red light ratio. Shade inhibits germination by altering hormonal pathways, increasing abscisic acid (ABA) and decreasing gibberellins (GA), which together promote dormancy. Molecular regulators, like PIL5, integrate light and hormonal signals to optimize germination timing. These mechanisms ensure seeds germinate only in conditions favourable for seedling survival.

(Peterhansel et al., 2010)

“Photorespiration”; examines the process by which plants metabolize 2-phosphoglycolate, a byproduct of Rubisco's oxygenation activity during photosynthesis. Photorespiration is an energy-intensive pathway involving multiple organelles (chloroplasts, peroxisomes, and mitochondria) to recycle this byproduct into usable molecules. While often viewed as wasteful, the authors highlight its roles in protecting plants from photoinhibition, maintaining redox balance, and recycling nitrogen and carbon. The paper also discusses genetic and metabolic approaches to reduce photorespiratory losses to improve crop productivity.

(Piovesan and Biondi, 2021)

“On tree longevity” ; discuss genetic, physiological, and ecological mechanisms that promote longevity, including robust defense systems, effective stress responses, and modular growth patterns. They highlight the role of environmental stability, minimal disturbances, and resource availability in fostering long lifespans. The study also emphasizes the importance of long-lived trees for ecosystems, carbon storage, and biodiversity, while addressing threats like climate change and human activities that challenge tree longevity.

(Webb and Mansfield, 1992)

“How do stomata work?”; Stomatal movements are controlled by changes in the turgor pressure of guard cells, driven by ion transport, osmotic adjustments, and water flow. Key factors influencing these processes include light, carbon dioxide concentration, humidity, and abscisic acid (ABA), particularly during stress conditions like drought. The paper highlights the integration of environmental signals and internal pathways that optimize stomatal function for water conservation and efficient photosynthesis.

(Loulakakis et al., 2009)

“Advancements in Nitrogen Metabolism in Grapevine” ; importance of nitrogen uptake, assimilation, and storage processes mediated by enzymes like nitrate reductase and glutamine synthetase. They discuss how nitrogen availability affects grapevine yield and the synthesis of compounds critical for wine production, such as amino acids and secondary metabolites.

(Dixon and Joly, 1894)

Cohesion-tension theory; proposed that water is pulled upward in xylem due to cohesion between water molecules and adhesion to vessel walls

(Willmer and Fricker, 1996)

ABA and stomatal closure

Redfield and Hutchinson (1950s)

nitrogen fixation in legumes by interaction with Rhizobium bacteria

(Borthwick et al., 1952)

Phytochrome discovery and its role in light-mediated seed germination and photomorphogenesis