Differential response of the photosynthetic machinery to dehydration in older and younger resurrection plants

Abstract

A group of vascular plants called homoiochlorophyllous resurrection plants evolved unique capabilities to protect their photosynthetic machinery against desiccation-induced damage. This study examined whether the ontogenetic status of the resurrection plant Craterostigma pumilum has an impact on how the plant responds to dehydration at the thylakoid membrane level to prepare cells for the desiccated state. Thus, younger plants (<four months) were compared with their older (>six months) counterparts. Ultrastructural analysis provided evidence that younger plants suppressed senescence-like programs that are realized in older plants. During dehydration, older plants degrade specific subunits of the photosynthetic apparatus like the D1 subunit of photosystem II and subunits of the cytochrome b6f complex. The latter leads to a controlled downregulation of linear electron transport. In contrast, younger plants increased photoprotective high-energy quenching mechanisms and maintained a high capability to replace damaged D1 subunits. It follows that depending on the ontogenetic state, either more degradation-based or more photoprotective mechanisms are employed during dehydration of Craterostigma pumilum.

Hurry Up and Wait: Managing the Inherent Mismatches in Time Scales in Natural and Artificial Photosynthetic Systems

“…Provision of buffering elements where reagents (electrons, protons, and molecular intermediates) can be stored temporarily would provide a very useful way to avoid idle catalytic centers and improve efficiency. Natural systems such as PSII do this by including channels that can control the flow of protons and water, and have mechanisms to dissipate excess electrons through cyclic electron transport . Accumulation of photogenerated electrons and holes in oxide semiconductors has been reported with the caveat that an increase in their concentration may increase losses through recombination.…”

“…To regulate the stoichiometry of ATP/NADPH, 96 an additional electron transport pathway exists that recycles electrons around PSI, called cyclic electron transport (CET) (Figure 10). 97 Unlike LET, CET is driven only by PSI, through the redirection of the electron flow from ferredoxin (Fd) to plastoquinone (PQ). This results in the production of ATP only without net NADPH synthesis, thus, increasing the ATP/NADPH ratio.…”

“…Natural systems such as PSII do this by including channels that can control the flow of protons and water, 121 and have mechanisms to dissipate excess electrons through cyclic electron transport. 97 Accumulation of photogenerated electrons 122 and holes 123 in oxide semiconductors has been reported with the caveat that an increase in their concentration may increase losses through recombination. Cross-surface electron transfer to accumulate redox equivalents in molecular catalyst-dye mixtures has been proposed.…”

Integrating leaf spectral and water status information to effectively track chlorophyll a fluorescence parameters during dehydration

“…Consistently, a drought experiment conducted byWu and Chen (2018) on Camphor tree species corroborated our findings, demonstrating an increase in heat dissipation capacity with an escalating drought gradient. The rapid increase of NPQ and ΦN during the early stages of dehydration can be attributed to a swift adjustment of the photoprotective mechanism to prevent damage to the photosynthetic apparatus(Oung et al 2022). Another possible reason is that C. sinensis and C. camphora, as typical evergreen species, have a higher heat dissipation capacity to compensate for water loss during dehydration.Ishida et al (…”