Pioneering research on C₄ leaf anatomical, physiological, and agronomic characteristics of tropical monocot and dicot plant species: Implications for crop water relations and productivity in comparison to C₃ cropping systems

Abstract

The review is done to summarise the history of the discoveries of the many anatomical, agronomical, and physiological aspects of C 4 photosynthesis (where the first chemical products of CO 2 fixation in illuminated leaves are four-carbon dicarboxylic acids) and to document correctly the scientists at the University of Arizona and the University of California, Davis, who made these early discoveries. The findings were milestones in plant science that occurred shortly after the biochemical pathway of C 3 photosynthesis in green algae (where the first chemical product is a three-carbon compound) was elucidated at the University of California, Berkeley, and earned a Nobel Prize in chemistry. These remarkable achievements were the result of ground-breaking pioneering research efforts carried out by many agronomists, plant physiologists and biochemists in several laboratories, particularly in the USA. Numerous reviews and books written in the past four decades on the history of C 4 photosynthesis have focused on the biochemical aspects and give an unbalanced history of the multidisciplinary/multinstitutional nature of the achievements made by agronomists, who published much of their work in Crop Science. Most notable among the characteristics of the C 4 species that differentiated them from the C 3 ones are: (I) high optimum temperature and high irradiance saturation for maximum leaf photosynthetic rates; (II) apparent lack of CO 2 release in a rapid stream of CO 2 -free air in illuminated leaves in varying temperatures and high irradiances; (III) a very low CO 2 compensation point; (IV) lower mesophyll resistances to CO 2 diffusion coupled with higher stomatal resistances, and, hence, higher instantaneous leaf water use efficiency; (V) the existence of the so-called "Kranz leaf anatomy" and the higher internal exposed mesophyll surface area per cell volume; and (VI) the ability to recycle respiratory CO 2 by illuminated leaves. PhD in crop physiology, The University of Arizona, Tucson, 1965]. For more than four decades, he has contributed to research in field crop production, breeding, and physiology of cotton, cereal crops and the root tropical crop cassava. He took a leading role in establishing a faculty of agriculture, Tripoli University, Libyan Arab Republic, and participated in the pioneering agricultural development projects under irrigation in the semiarid and arid ecosystems of North Africa and the Sahara. Abbreviations: C i − intercellular CO 2 concentration; DM − dry mass; NAD-ME − NAD-dependent malic enzyme; NADP-ME − NADP-dependent malic enzyme; PAR − photosynthetically active radiation; PCK − phosphoenolpyruvate carboxykinase; PCRC − photosynthetic carbon reduction cycle − PEPC − phosphoenolpyruvate carboxylase; PGA − 3-phosphoglycerate; PNUE − photosynthetic nitrogen use efficiency; PPDK − pyruvate orthophosphate dikinase; P N − leaf net photosynthetic rate; r m − mesophyll resistances to CO 2 diffusion; r k − intracellular resistances to CO 2 diffusion; Rubisco − ribulose-1,5-bisphosphate carboxylase/ ...

Rooting for cassava: insights into photosynthesis and associated physiology as a route to improve yield potential

“…Some studies on these cultivars have suggested that cassava uses a C 3 –C 4 intermediate form of photosynthesis on account of high leaf photosynthetic rates, low apparent rates of photorespiration, a chlorenchymatous bundle sheath and a high photosynthetic nitrogen (N) use efficiency (El‐Sharkawy & Cock, ; El‐Sharkawy, , ). Parallel work feeding 14 CO 2 to leaves of cassava showed an apparent intermediate pattern of initial C 4 and C 3 products (Cock et al ., ).…”

Large Root Cortical Cell Size Improves Drought Tolerance in Maize

“…However, the relationship between cell size and photosynthesis remains unresolved, as illustrated by the contradictory hypotheses put forward by several authors. A negative correlation between photosynthesis and mesophyll cell size in several species was reported (El-Sharkawy and Hesketh, 1965;Wilson and Cooper, 1970;El-Sharkawy, 2009), attributed to the increase in cell surface area per volume with reduced cell size, but Dornhoff and Shibles (1976) observed no correlation between photosynthesis and cell size in soybean (Glycine max). In contrast, others (Warner et al, 1987;Edwards, 1988, 1989) argued that large cells have greater photosynthetic capacity than smaller cells.…”

Stereology, an Unbiased Methodological Approach to Study Plant Anatomy and Cytology: Past, Present and Future

“…This approach is precise and more efficient (especially the fakir method in combination with confocal microscopy as shown by Albrechtová et al, 2007) than model-based methods. Its advantages have been acknowledged by other authors (El-Sharkawy, 2009). …”