Regulation of curcuminoids, photosynthetic abilities, total soluble sugar, and rhizome yield traits in two cultivars of turmeric (Curcuma longa) using exogenous foliar paclobutrazol

Paclobutrazol (PBZ) is a member of plant growth retardants, commonly applied for growth regulation, yield improvement, and biotic and abiotic stress alleviation. However, the effects of PBZ on turmeric (Curcuma longa L.; Zingiberaceae), a rhizomatous herb, have not been well established. The objective of this investigation was to gain a better understanding of the effect of PBZ on two different varieties of turmeric plants, ‘Surat Thani’ (‘URT’; high curcuminoids >5% w/w) and ‘Pichit’ (‘PJT’; low curcuminoids <3% w/w). Pseudostem height of cv. ‘PJT’ treated by 340 µM PBZ was significantly decreased by 14.82% over control, whereas it was unchanged in cv. ‘URT’. Interestingly, leaf greenness (SPAD value), maximum quantum yield of PSII (Fv/Fm) and photon yield of PSII (ΦPSII) in cv. ‘PJT’ treated by 340 µM PBZ were significantly elevated by 1.47, 1.28 and 1.23 folds, over control respectively. Net photosynthetic rate (Pn) in cv. ‘PJT’ declined by 38.58% (340 µM PBZ) over control, as a result of low levels of total soluble sugars (TSS; 127.8 mg g-1 DW) in turmeric rhizome. A positive relation between photosynthetic abilities and aerial fresh weight was demonstrated. In addition, a negative relationship between TSS and total curcuminoids was evidently found (R2 = 0.4524). Curcuminoids yield in turmeric rhizomes significantly dropped, depending on the degree of exogenous foliar PBZ applications. In summary, cv. PJT was found to be very sensitive to PBZ application, whereas rhizome yield and growth traits and high amount of curcuminoids were retained in cv. ‘URT’. Plant growth retention in turmeric cv. ‘URT’ using 170 mM PBZ foliar spray without negative effects on rhizome biomass and total curcuminoids content was demonstrated

Matching of Nitrogen Enhancement and Photosynthetic Efficiency by Arbuscular Mycorrhiza in Maize (Zea mays L.) in Relation to Organic Fertilizer Type

In the present study, Funneliformis mosseae (FM), Claroideoglomus etunicatum (CE), and Acaulospora foveata (AF) were inoculated to hybrid maize (Zea mays L. cv. CP888®). Upregulation of nitrogen levels were dependent on the type of mycorrhiza (AMF). Photosynthetic efficiency (Fv/Fm) and water content in FM- and AF-inoculated plants were elevated, resulting in promotion of leaf area and shoot biomass. N content in the shoot and root tissues of the FM-inoculated plants increased by 21% and 30% over the control. A positive correlation between biochemical, physiological, and morphological parameters using Pearson’s coefficient was demonstrated. A decline in lipid peroxidation was noticed in the FM-inoculated plants. In addition, we investigated the potential of N fertilizer application in combination with FM inoculation in maize plants. The FM-inoculated plants with organic O_LT, a chicken manure fertilizer, increased N content in the host shoots by 73% over the control, leading to improved Fv/Fm as a physiological adaptation strategy. The FM and the O_LT on the regulation of the N enhancement and photosynthetic efficiency of the hybrid maize should further be validated in field trials in different environments for sustainability