Research Projects

From simple algal forms to the most advanced angiosperms, calcium oxalate (CaOx) crystals exhibit their occurrence in nearly all taxonomic echelons of photosynthetic organisms. This biomineralization is not a simple or random event, instead, a genetically regulated coordination between calcium uptake, oxalate synthesis, and environmental stresses [1]. The CaOx crystals are regarded as the dynamic storage systems which can supply both calcium as well as oxalate— mobilized to release CO2 as an internal carbon source— to perform vital functions. Though speculative, a suit of important utilities are ascribed to the CaOx crystals. A vital aspect of these biominerals is their ability to reflect/scatter light to avoid photodamage [2], and to perform Alarm photosynthesis (AP) [3-6]. Latter is supposed to utilize the reservoir of CaOx crystals as a dynamic internal carbon source thereby affording to prevent water loss through stomatal pores. AP is thought to provide a base level of activity during times of reduced stomatal conductance by promoting the stability and avoidance of photoinhibition of photosystem II [7]. So, understanding the mechanism of this phenomenon could provide a potential platform to address the future climate change-associated food security issues concomitant with the yield of non-crystal accumulating crops under stress; drought, for instance. Certainly, we can prevent the lethal and drought-driven carbon limitations to dream of developing drought-resistant plant cultivars while utilizing the dynamic abilities of CaOx crystal-bearing plants. In this context, while assessing certain parameters, we hypothesize CaOx crystals as anticipated sources of supplemental carbon for photosynthesis in environments where the atmospheric supply of CO2 is unfavorable. In light of our decade-long association with rhubarb [8-16], pertinently, and compared to the literature records, we have found much abundance (36% of plant dry weight) of CaOx crystals in R. tibeticum from the whole gamut of five Rheum species growing in the northwest Indian Himalayas. The species, with grounded and leather-textured leaves, was found to grow in sandy soil or rock cliffs at an elevation of 2900-4200 m asl having extremely xerophytic conditions with higher incoming solar radiation. Our preliminary investigations (*Pandith et al., 2023; 1 Manuscript, 1 Review, and 1 PATENT) have raised a number of interesting questions as follows: (i) Under harsh environmental conditions (limited water and supposedly reduced mesophyll conductance due to high light intensities), how the species efforts to maintain normal growth with heavy loads of CaOx crystals? (ii) Does the species synthesize and accumulate these crystals as calcium (for its mobilization), and carbon reservoirs to drive the subsidiary mode of photosynthesis? (iii) If yes, how far the expression pattern of the CaOx regulation genes matches our speculations? To address these questions, the following objectives are chosen: