The response of Stevia (Stevia rebaudiana Bertoni) to nitrogen supply under greenhouse condition

Stevia (Stevia rebaudiana Bertoni) is a perennial plant producing some natural sweeteners. Stevia is considered as a new crop in some countries. This study was conducted to find the stevia response to nitrogen fertilizer supply. Different levels of nitrogen (0, 30, 60, 90, 120, and 150 kg/ha from urea source) were used in a greenhouse condition and then the stevia growth and metabolites were assessed under different availability of nitrogen. Results showed that the optimum growth of stevia was obtained by 60 kg/ha nitrogen and more nitrogen supply did not enhance the stevia growth. It was observed that the total steviol glycosides (SVglys) content of Stevia was significantly increased by nitrogen fertilizer application just up to 30 kg/ha, while it decreased by more rates of nitrogen fertilizer. Our result clearly showed that SVglys yield reached to maximum value by application of 60 kg/ha of nitrogen fertilizer. Since the variation of SVglys content and shoot growth of the stevia were compromised by 60 kg/ha nitrogen, it can be concluded that 60 kg/ha of nitrogen fertilizer could be considered as an optimum rate of nitrogen for stevia and could also be recommended for greenhouse conditions.     

Zinc influence and salt stress on photosynthesis,water relations,and carbonic anhydrase activity in pistachio

A greenhouse study was conducted to evaluate the ameliorative effects of zinc (0, 5, 10 and 20 mg Zn kg⁻¹ soil) under saline (800, 1600, 2400 and 3200 mg NaCl kg⁻¹ soil) conditions on pistachio (Pistacia vera L. cv. Badami) seedlings’ photosynthetic parameters, carbonic anhydrase activity, protein and chlorophyll contents, and water relations. Zn deficiency resulted in a reduction of net photosynthetic rate and stomatal conductance. The quantum yield of photosystem II was reduced at zinc deficiency and salt stress. Zinc improved plant growth under salt-affected soil conditions. Increasing salinity in soil under Zn-deficient conditions, generally decreased carbonic anhydrase activity, protein, chlorophyll a and b contents. However, these adverse effects of salinity alleviated by increasing Zn levels up to 10 mg kg⁻¹ soil. Under increasing salinity, chlorophyll a/b ratio significantly increased. Zinc treatment influenced the relationship between relative water content and stomatal conductance, and between leaf water potential and stomatal conductance. It concluded that Zn may act as a scavenger of ROS for mitigating the injury on biomembranes under salt stress. Adequate Zn also prevents uptake and accumulation of Na in shoot, by increasing membrane integrity of root cells.     

Evaluation of Physico-Chemical Properties and Bioactive Compounds of Some Iranian Pomegranate Cultivars

Persia is one of the main origin centers of pomegranate; hence, a diverse germplasm has evolved in the area over the past centuries. This study was conducted to evaluate the physico-chemical properties of fruits of ten Persian pomegranate cultivars. The plants used for this experiment had been collected from different parts of Iran and were established in a repository. Wide variations in the main properties of the ripe fruits of the cultivars were observed. The size, weight, skin thickness and weight, and juice content of the fruits were within the range of 55.14–71.76 mm, 98.55–199.40 g, 1.07–3.93 mm, 28.96–66.95 g, and 2.00–89.33 ml, respectively. Seed weight, Aril numbers, fresh and dry weight of 100 arils were 33.80–72.90 g, 170.70–570.30, 23.16–42.82 g, and 17.22–33.87%, respectively. The levels of total anthocyanin, total soluble solids (TSS), titrable acidity (TA), ascorbic acid, total phenolics, electrical conductivity, and TSS/TA ratio were ranged between 5.91–180.70 mg/100 g, 9.35–13.93 °Brix, 0.16–2.28%, 7.15–1061 mg/100 ml, 3578–5108 mg/100 g, 2.51–4.93 dS/m, and 4.09–80.34, respectively. The results emphasized on the role of plant genotype on fruit taste parameters, bioactive compounds, and yield. The variations in the fruits indicated differences in nutritive quality, which may satisfy diverse consumer acceptance in different areas. Moreover, it provides great opportunities for improving crop yield and quality.