Silica is deposited extra- and intracellularly in plants in solid form, as phytoliths. Phytoliths have emerged as accepted taxonomic tools and proxies for reconstructing ancient flora, agricultural economies, environment, and climate. The discovery of silicon transporter genes has aided in the understanding of the mechanism of silicon transport and deposition within the plant body and reconstructing plant phylogeny that is based on the ability of plants to accumulate silica. However, a precise understanding of the process of silica deposition and the formation of phytoliths is still an enigma and the information regarding the proteins that are involved in plant biosilicification is still scarce. With the observation of various shapes and morphologies of phytoliths, it is essential to understand which factors control this mechanism. During the last two decades, significant research has been done in this regard and silicon research has expanded as an Earth-life science superdiscipline. We review and integrate the recent knowledge and concepts on the uptake and transport of silica and its deposition as phytoliths in plants. We also discuss how different factors define the shape, size, and chemistry of the phytoliths and how biosilicification evolved in plants. The role of channel-type and efflux silicon transporters, proline-rich proteins, and siliplant1 protein in transport and deposition of silica is presented. The role of phytoliths against biotic and abiotic stress, as mechanical barriers, and their use as taxonomic tools and proxies, is highlighted.

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In the halophytic species Mesembryanthemum crystallinum, the induction of crassulacean acid metabolism (CAM) by salinity requires a substantial investment of resources in storage carbohydrates to provide substrate for nocturnal CO2 uptake. Acclimation to salinity also requires the synthesis and accumulation of cyclitols as compatible solutes, maintenance of root respiration, and nitrate assimilation. This study assessed the hierarchy and coordination of sinks for carbohydrate in leaves and roots during acclimation to salinity in M. crystallinum. By comparing wild type and a CAM-/starch-deficient mutant of this species, it was sought to determine if other metabolic sinks could compensate for a curtailment in CAM and enable acclimation to salinity. Under salinity, CAM deficiency reduced 24 h photosynthetic carbon gain by >50%. Cyclitols were accumulated to comparable levels in leaves and roots of both the wild type and mutant, but represented only 5% of 24 h carbon balance. Dark respiration of leaves and roots was a stronger sink for carbohydrate in the mutant compared with the wild type and implied higher maintenance costs for the metabolic processes underpinning acclimation to salinity when CAM was curtailed. CAM required the nocturnal mobilization of >70% of primary carbohydrate in the wild type and >85% of carbohydrate in the mutant. The substantial allocation of carbohydrate to CAM limited the export of sugars to roots, and the root:shoot ratio declined under salinity. The data suggest a key role for the vacuole in regulating the supply and demand for carbohydrate over the day/night cycle in the starch-/CAM-deficient mutant.

In this paper, a crude methanolic extract from the stem bark of Prosopis cineraria, a plant native of Pakistan, was tested for its possible presence of spasmolytic, bronchodilator, and vasodilator activities in an attempt to validate some of its folkloric uses. Moreover, attempts were made to provide plausible explanations of the observed biological activities. The extract caused relaxation of the spontaneous as well as K+ (80 mM)-induced contractions at tissue bath concentrations of 3–10 mg/mL in isolated rabbit jejunum preparations, probably mediated through blockade of Ca+2 channels. This finding was further confirmed by the shifting of the Ca+2 concentration response curves to the rightward in a manner similar to verapamil used as a standard Ca+2 channel blocker. The extract also exhibited nonspecific relaxant effect on carbachol (1 μM)- and K+ (80 mM)-induced contractions in isolated rabbit tracheal preparations. The same effect was recorded for phenylephrine (11 μM) and K+ (80 mM)-induced contractions in isolated rabbit aortic preparations in a manner similar to verapamil. These observations confirm that observed bronchodilator and vasodilator activities were possibly mediated through blockade of Ca+2 channels. The above-mentioned observations validate the traditional use of the plant in the treatment of respiratory and gastrointestinal ailments.

Zinc (Zn) is an essential element for humans, animals and plants, however, its deficiency has been widely reported around the world especially in flooded rice. Adequate amount of Zn is considered essential for optimum growth and development of rice. We hypothesised that management practices like Zn-mineral fertiliser, -compost, and -solubilising bacteria would improve Zn availability and uptake in flooded rice. A series of studies were conducted to find out the comparative efficacy of Zn-enriched composts (Zn-ECs) with Zn solubilising bacteria (ZnSB) vs. ZnSO4 for improved growth, yield and Zn accumulation in rice. There were six treatments viz. control, ZnSB, ZnO (80% Zn), ZnSO4 (33% Zn), Zn-EC80:20 and Zn-EC60:40. In all the treatments, Zn was applied at the rate of 5 kg ha–1 except the control. The treatment Zn-EC60:40 resulted in the maximum Zn release in soil as compared to ZnSO4 and all other treatments during incubation study. The treatment Zn-EC60:40 significantly improved root dry weight, grain yield and 100-grain weight of rice by 15, 22 and 28%, respectively as compared to ZnSO4. The same treatment resulted in the maximum increase in photosynthetic rate (11%), transpiration rate (21%), stomatal conductance (17%), chlorophyll contents (8%) and carbonic anhydrase activity (10%) while a decrease of 27% in electrolyte leakage was observed in comparison with ZnSO4 application. Moreover, the maximum increase in grain quality parameters and Zn bioaccumulation was observed with the application of Zn-EC60:40 in comparison with ZnSO4 application and all other treatments. We conclude that Zn-EC60:40 are not only an effective strategy to improve growth, physiology and yield parameters of rice, but also to improve the grain quality and Zn-bioaccumulation in rice compared to ZnSO4.