Role of cotton sticks biochar in immobilization of nickel under induced toxicity condition and growth indices of Trigonella corniculata L.

Among various heavy metals, nickel (Ni) is a potential pollutant that accumulates in broad-leaf vegetables and is reported to be carcinogenic. Biochar (BC) is a nutrient-rich and effective organic amendment for immobilization of Ni in soil. Fenugreek (Trigonella corniculata L.), a broad-leaf vegetable, is commonly cultivated due to its all-inclusive composition of nutrients such as calcium and iron and ß-carotene and vitamins. Therefore, a field-pot study was conducted to examine the effectiveness of cotton-sticks-waste biochar (BC) for soil immobilization of Ni in fenugreek crop cultivated between early-October to end-November 2015. Fenugreek was grown in a sandy-loam soil experimentally contaminated with various Ni levels (0, 25, 50, and 100 mg Ni kg-1 soil) under three BC levels (0, 3, and 5%; w/w). Overall, results showed increasing plant lipid peroxidation (assessed via malondialdehyde) and ascorbic-acid concentration with increasing Ni toxicity level without BC application (p ≤ 0.05). Application of 3% BC increased the chlorophyll a (20.0%), chlorophyll b (49.1%), total chlorophyll (27.6%), carotenoids (21.6%), anthocyanin (27.2%), photosynthetic rate (112%), transpiration rate (45.0%), and sub-stomatal CO2 concentration (19.9%) in fenugreek as compared to control (0% BC) under 50 mg Ni kg-1 soil. Higher BC application rate (5%) was more effective in increasing the chlorophyll a (33.6%), chlorophyll b (81.1%), total chlorophyll (43.9%), carotenoids (71.7%), anthocyanin (77.8%), photosynthetic rate (127%), transpiration rate (42.2%), and sub-stomatal CO2 concentration (23.5) over control under 100 mg Ni kg-1 soil. We suggest that the consistent increases in dry mass, carbon flux rate and, protein, amino acids, and sugar contents of fenugreek (cultivated in a soil toxified with Ni and amended with 5% BC) seems to be caused by the reduction in the mobility of Ni in the presence of BC in a sandy-loam soil.

Pollination biology of Albizia lebbeck (L.) Benth. (Fabaceae: Mimosoideae) with reference to insect floral visitors.

Indian siris, Albizia lebbeck (L.) Benth. (Fabaceae: Mimosoideae) has significant importance to human beings for its multipurpose use. Insects play a crucial role in the pollination biology of flowering plants. In the current study, we studied the pollination biology of A. lebbeck with special reference to insect floral visitors. The effectiveness of floral visitors was investigated in term of visitation frequency, visitation rate and pollen load during 2012 and 2013. In the second experiment, effect of pollinators on yield of A. lebbeck was studied in open and cage pollination experiments. Floral visitor fauna of A. lebbeck included eight-bees, two wasps, two flies, and two butterflies species. Among them, Apis dorsata, Apis florea, Amegilla cingulata, and Nomia oxybeloides had maximum abundance ranging from 349-492, 339-428, 291-342 and 235-255 numbers of individuals, respectively during two flowering seasons. A. dorsata had the highest visitation frequency (6.44 ±â€¯0.49-8.78 ±â€¯0.48 visits/flower/5min) followed by Amegilla cingulata (6.03 ±â€¯0.43-7.99 ±â€¯0.33 visits/flower/5min) and A. florea (3.61 ±â€¯0.31-4.44 ±â€¯0.18 visits/flower/5min). A. dorsata, N. oxybeloides, and Amegilla cingulata had the highest visitation rates (18.904 ±â€¯1.53-11.43 ±â€¯1.17 flower visited/min) and pollen load (15333 ±â€¯336.22-19243 ±â€¯648.45 pollen grains). The open pollinated flowers had significantly higher capsule weight (4.97 ±â€¯0.21 g), seed weight (1.04 ±â€¯0.05 g), seed numbers per pod (9.80 ±â€¯0.34) and seed germination percentage (84.0 ±â€¯1.78%) as compared to caged flowers. The results suggested bees especially A. dorsata, N. oxybeloides and Amegilla cingulata could be effective pollinators of A. lebbeck.

Biochar enhances the cadmium tolerance in spinach (Spinacia oleracea) through modification of Cd uptake and physiological and biochemical attributes.

Cadmium (Cd) has no known role in plant biology and is toxic to plants and animals. The Cd mainly accumulated in agricultural soils through anthropogenic activities, such as sewage water irrigation and phosphorus fertilization. Biochar (BC) has been proposed as an amendment to reduce metal toxicity in plants. The objective of this study was to evaluate the role of BC (cotton stick at a rate of 0, 3, and 5 %) on Cd uptake and the photosynthetic, physiological, and biochemical responses of spinach (Spinacia oleracea) grown in Cd-spiked soil (0, 25, 50, 75, and 100 mg Cd kg-1 soil). The results showed that Cd toxicity decreased growth, photosynthetic pigments, gas exchange characteristics, and amino acid and protein contents in 52-day-old spinach seedlings. The Cd treatments increased the concentrations of Cd, sugar, ascorbic acid, and malondialdehyde (MDA) in plants. The application of BC ameliorated the harmful effects of Cd in spinach plants. Under Cd stress, BC application increased the growth, photosynthesis, and protein contents and decreased Cd concentrations and MDA contents in plants. The maximum BC-mediated increase in dry biomass was about 25 % with 5 % BC application in control plants. It is concluded that BC could ameliorate Cd toxic effects in spinach through changing the physiological and biochemical attributes under Cd stress.