Photosynthesis

Abstract

Cacao and chocolate production is a global industry worth around $133 billion. Full sun cultivation is a modern approach aimed at increasing yields. We evaluated six cacao clones (PS 1319, CCN 10, CCN 51, PH 16, SJ 02, and CP 49) grown under full sun conditions to assess their leaf physiology, leaf structure, yield, and yield components. Leaf physiology was measured through seven gas exchange parameters, while leaf structure was analyzed using eight measurements. For fruit and seed, we evaluated seven yield components. The clones showed differences in gas exchange. Clones PH 16 and PS 1319 had higher net photosynthetic rates per unit of leaf area (A), transpiration rates, and lower leaf internal CO2 concentrations. These A high values suggest the clones are well-acclimatized to full sun cultivation. Water availability, nutrient supply, and appropriate plant architecture also contributed to this acclimatization. Under high light intensity, the potential quantum yield of photosystem II indicated no photoinhibition, and adaptations in the photosynthetic apparatus were observed, such as lower pigment concentration in clone PH 16. Clones differed in specific leaf area (SLA) and stomatal density (SD). CCN 51 had a higher SLA, while SJ 02 had a higher SD. A significant negative correlation (-0.89) was found between dry bean yield and leaf-to-air water vapor pressure deficit (VpdL), suggesting that VpdL is a crucial parameter for selecting high-performance clones for fertigated full sun cultivation. Yields ranged from 1,220 kg/ha (CCN 10) to 2,900 kg/ha (CCN 51). Full sun cacao farms have high yield potential due to a combination of cloning, management practices, and adequate water and nutrient availability.

I love varigated plants and have a ton of them. I'm continually amazed at what leaves manage to survive if they're not completely white, and sometimes those white leaves just hang on longer than they should. Please ELI5, someone how these zombie creatures survive and flourish?

This is a book that I strongly to anyone with a reasonable biochemistry/chemistry background. Reading this book inspired me to create a community dedicated to photosynthesis, because I want to follow the work in this field more closely.

Photosynthesis is a topic introduced early during our education. We are taught that light consists of bundles of energy, and that plants use the energy from carried by sunlight to build carbohydrates from water and CO2.

Around high school and in introductory college level classes many of us also learn that plants are green because of the chlorophyll molecules, which absorb the blue and the red regions of the spectrum and leave enough green behind to be reflected. The absorbed light is used to kick-out an electron from a magnesium ion that is held at the center of the chlorophyll molecules, and this electron begins a sequence of redox reactions that eventually leads to the production of metabolic energy and carbohydrates.

This simplified description provides one with the the overall picture of the process, and it is more than sufficient for most people. But my gripe with this description is that many students may leave photosynthesis class without realizing just how spectacular and complex the system actually is.

The photosynthetic machinery is by far the most advanced light-harvesting system that we know of. It uses a combination of many multiple physical principles - efficient energy transfer processes to move energy from light harvesting antennas into reaction centers, the ability to selectively funnel energy into non-radiative and non-photochemical quenching channels as a photoprotective mechanism, it utilizes as-of-today poorly understood 'superexchange' electron transfer mechanisms, and many more things that you can learn about in the recommended book.

There is also the added complexity that photosynthesis is extremely diverse, with different organisms having evolved very different solutions to meet their specific needs. Here is a figure from the text in which the photosynthetic assemblies from different types of organisms are compared:

Maybe this post can inspire someone to take a look at this book. And, if so, hopefully they will also find a lot of value in it!

The actual paper is:

Wang, Dihao, et al. "Elucidating interprotein energy transfer dynamics within the antenna network from purple bacteria." Proceedings of the National Academy of Sciences of the United States of America 120.28 (2023): e2220477120.