The efficiency of nanoparticles covered with type A gel and loaded with KH₂PO₄, as a source of P, was evaluated on growth, phosphorus concentration and accumulation, and photosynthesis-related parameters in rice plants (Oryza sativa L. ssp. indica) cv. Morelos A-2010, under greenhouse conditions. Plants were treated for 14 days with P concentrations equivalent to 50 and 100% of those established in the Yoshida nutrient solution. Sources of P were KH₂PO₄, nano-KH₂PO₄, and nano-KH₂PO₄ with trypsin; control treatments were distilled water and nanoparticles with type A gel. The solutions were renewed every 7 d. Rice plants exhibited differential P absorption in function of the P source tested. P supplied by KH₂PO₄ had a higher uptake rate than P supplied by nano-KH₂PO₄, alone or with trypsin. Nevertheless, nano-KH₂PO₄ promoted higher physiological efficiency for P in both roots and shoots, which consequently induced higher biomass accumulation in these organs. P concentration in shoots, as well as P accumulation in shoots and roots, were positively correlated with the photosynthetic rate. Also, nano-KH₂PO₄ increased instant water use efficiency in rice plants.

Lanthanum (La) is considered a beneficial element, capable of inducing hormesis. Hormesis is a dose-response relationship phenomenon characterized by low-dose stimulation and high-dose inhibition. Herein we tested the effect of 0 and 10 µM La on growth and biomolecule concentrations of seedlings of four sweet bell pepper (Capsicum annuum L.) varieties, namely Sven, Sympathy, Yolo Wonder and Zidenka. Seedling evaluations were performed 15 and 30 days after treatment applications (dat) under hydroponic greenhouse conditions. Seedling height was significantly increased by La, growing 20% taller in Yolo Wonder plants, in comparison to the control. Similarly, La significantly enhanced shoot diameter, with increases of 9 and 9.8% in measurements performed 15 and 30 dat, respectively, as compared to the control. Likewise, La-treated seedlings had a higher number of flower buds than the control. An increase in the number of leaves because of La application was observed in Yolo Wonder seedlings, both 15 and 30 dat, while leaf area was augmented in this variety only 30 dat. Nevertheless, La did not affect dry biomass accumulation. La effects on biomolecule concentration were differential over time. In all varieties, La stimulated the biosynthesis of chlorophyll a, b and total 15 dat, though 30 dat only the varieties Sympathy and Yolo Wonder showed enhanced concentrations of these molecules because of La. Total soluble sugars increased in La-treated seedlings 30 dat. Interestingly, while most varieties exposed to La showed a reduction in amino acid concentration 15 dat, the opposite trend was observed 30 dat. Importantly, in all varieties evaluated, La stimulated soluble protein concentration 30 dat. It is important to note that while chlorophyll concentrations increased in all varieties exposed to La, both 15 and 30 dat, those of soluble sugars and proteins consistently increased only 30 dat, but not 15 dat. Our results confirm that La may improve seedling quality by enhancing some growth parameters and biomolecule concentrations, depending on the genotype and time of exposure.

The rare earth element (REE) cerium (Ce) can act as a biostimulant in diverse crop plants. The effects of 0, 5, 10, and 15 µM Ce (supplied as CeCl₃ 7H₂O) on seed germination and the initial growth of tomato (Solanum lycopersicum L.) cv. Vengador were evaluated. After a 12 h imbibition, the weight of the seeds treated with 15 µM Ce was 37.5% greater than that observed in the control. The germination index of the seeds treated with 5 µM Ce was greater than 100% (101.93%), though when applying 10 µM Ce this index was 17.53% lower than the control seeds. Nevertheless, Ce treatments did not significantly affect the coefficient of velocity of germination, relative seed germination, germination index, radicle length, dry biomass, or relative growth. Interestingly, shoot length increased significantly in the treatments with 5, 10, and 15 µM Ce. This tendency was also observed in the dry biomass weight and relative growth of the shoots. Hence, Ce has a stimulating effect on germination and initial growth in tomato cv. Vengador shoots. In particular, there was a priming effect of Ce on seeds, reflected in a higher weight gain in Ce-treated seeds, which indicated greater water absorption. Therefore, Ce can be an alternative to accelerate the production time of tomato seedlings in seedbeds.

It is possible to have a higher efficient use of water in a greenhouse because there is a better control of environmental conditions for crop production (^{Costa et al., 2018}), including tomato as one of the most cultivated vegetables due to its profitability and its consumption (^{Krause et al., 2017}).

The chilhuacle chili (Capsicum annuumL.) is a Mexican native variety whose production has been highly valuable because it is the main ingredient of the Oaxacan black mole, a typical Mexican dish. It is basically grown in the Cañada Region of the State of Oaxaca, Mexico, within the Tehuacán-Cuicatlán Biosphere Reserve. Importantly, it is cultivated under traditional agricultural systems, where a range of agronomic constraints associated with the production process and the incidence and severity of pests and diseases represent significant impediments that hinder the yield potential. Additionally, the genetic basis of the crop is highly restricted. Under such environmental and production conditions, the mean crop yield of chilhuacle chili can reach 1 t ha⁻¹of dehydrated fruits, which can be used in the food, chemical, and pharmaceutical industries. In this review we summarize the current progress on chilhuacle chili cultivation and outline some crucial guidelines to improve production, as well as other research topics that need to be further addressed.