Effects of Effects of light, nutrient and grass competition on growth of seedlings of four tropical tree species

The seedling stage is a sensitive and important stage in plant life. Hence, a thorough understanding of the ecology of individual species and environmental characteristics affecting seedling growth is necessary. Resources such as water, nutrient and light are the most important limiting factors that influence seedling survival and establishment. However, the effect of these environmental factors is modified by grass competition in tropical dry forests. In this study, we examined the effects of light and nutrient with and without grass on the growth of seedlings of four common dry tropical plant species, viz. Acacia catechu, Acacia nilotica ssp. indica, Ziziphus mauritiana and Terminalia arjuna. The growth parameters including height, girth, total dry weight, leaf area and number of leaves, relative growth rate in terms of height, diameter and dry weight were recorded for each species under different treatment combinations. All the species behaved differently under studied treatment combinations. Seedlings were more responsive to the nutrient addition in presence of light. Presence of grass had overall negative effect on growth of tree seedlings. Survival was found highest for A. nilotica ssp. indica and lowest for Z. mauritiana while reverse trend was observed for overall growth. We infer from the results that supplementation of nutrients have strong positive effect over the seedling survival and growth even under reduced light and presence of grass competition. Moreover, the findings also revealed that the regular weeding and nutrient supplementation under the existing forest vegetation may help in regeneration of the dry tropical vegetation by reducing seedling mortality even under dense canopy conditions

Monogalactosyl Diacylglycerol Synthase 3 (OsMGD3) affects phosphate utilization and acquisition in rice

Galactolipids are essential for compensating for the loss of phospholipids by "membrane lipid remodeling" in plants under phosphorus (P) deficiency. Monogalactosyl diacylglycerol (MGDG) synthases catalyze the synthesis of MGDG which is further converted into digalactosyl diacylglycerol (DGDG), later replacing phospholipids in the extraplastidial membranes. However, the roles of these enzymes are not well explored in rice. In this study, the rice MGDG synthase gene, OsMGD3 was identified and functionally characterized. We showed that plant phosphate (Pi) status and transcription factor OsPHR2 are involved in the transcriptional regulation of OsMGD3. CRISPR/Cas9 knockout (KO) and overexpression (OE) lines of OsMGD3 were generated to explore its potential role in rice adaptation to Pi deficiency. Compared to WT, OsMGD3 KO lines displayed a reduction while OE lines showed an enhanced, Pi acquisition and utilization. Further, OsMGD3 showed a predominant role in roots, altering lateral root growth. Our comprehensive lipidomic analysis revealed the role of OsMGD3 in membrane lipid remodeling in addition to a role in regulating diacylglycerol and phosphatidic acid levels that affected the expression of Pi transporters. Our study highlights the role of OsMGD3 in affecting both internal P utilization and P acquisition in rice