Models Analyses for Allelopathic Effects of Chicory at Equivalent Coupling of Nitrogen Supply and pH Level on F. arundinacea, T. repens and M. sativa

Alllelopathic potential of chicory was investigated by evaluating its effect on seed germination, soluble sugar, malondialdehyde (MDA) and the chlorophyll content of three target plants species (Festuca arundinacea, Trifolium repens and Medicago sativa). The secretion of allelochemicals was regulated by keeping the donor plant (chicory) separate from the three target plant species and using different pH and nitrogen levels. Leachates from donor pots with different pH levels and nitrogen concentrations continuously irrigated the target pots containing the seedlings. The allelopathic effects of the chicory at equivalent coupling of nitrogen supply and pH level on the three target plants species were explored via models analyses. The results suggested a positive effect of nitrogen supply and pH level on allelochemical secretion from chicory plants. The nitrogen supply and pH level were located at a rectangular area defined by 149 to 168 mg/l nitrogen supply combining 4.95 to 7.0 pH value and point located at nitrogen supply 177 mg/l, pH 6.33 when they were in equivalent coupling effects; whereas the inhibitory effects of equivalent coupling nitrogen supply and pH level were located at rectangular area defined by 125 to 131 mg/l nitrogen supply combining 6.71 to 6.88 pH value and two points respectively located at nitrogen supply 180 mg/l with pH 6.38 and nitrogen supply 166 mg/l with pH 7.59. Aqueous extracts of chicory fleshy roots and leaves accompanied by treatment at different sand pH values and nitrogen concentrations influenced germination, seedling growth, soluble sugar, MDA and chlorophyll of F. arundinacea, T. repens and M. sativa. Additionally, we determined the phenolics contents of root and leaf aqueous extracts, which were 0.104% and 0.044% on average, respectively

Hydrogels Based on Starch from Various Natural Sources: Synthesis and Characterization

Hydrogels based on a graft copolymer of acrylic acid (AA) and acrylamide (AAm) on a backbone of starch, obtained from different natural sources, have been prepared and characterized for potential agricultural use, as soil moisture regulators and nutrient sources for plant nutrition. Five types of starch are used: corn, waxy corn, wheat, potato, and rice starch. Hydrogels are prepared by a solution polymerization method, in the presence of ammonium persulphate (PSA) as initiator and N,N'-methylene-bis-acrylamide (MBA) as a cross-linking agent. Thermal and physico-chemical properties, such as thermogravimetry analysis and differential scanning calorimetry data and swelling properties of hydrogels, are observed. The influences of the cross-linking agent on the swelling ratio (SR) and solubility of prepared hydrogels are studied and optimized. The highest SR observed in water corresponded to non-cross-linked hydrogels prepared with waxy corn starch (780 g water per g dry matter), and the SR of these hydrogels in ammonium sulfate and calcium nitrate solutions are 9.6 and 1.2 g per g dry matter, respectively. Higher thermal stability is observed with cross-linked starch-g-(AA-AAm) hydrogels. The non-cross-linked hydrogels have a higher SR, but also have significant solubility in water.Byly připraveny hydrogely na bázi roubovaného kopolymeru škrobu z různých přírodních zdrojů, kyseliny akrylové a akryl amidu. Připravené hydrogely byly charakterizovány pro agrochemické účely, jako regulátor vlhkosti nebo jako nosič živin pro výživu rostlin. Pro syntézu bylo použito pět různých škrobů: kukuřičný, voskový kukuřičný, pšeničný, bramborový a rýžový. Hydrogely byly polymerizovány v roztoku v přítomnosti persíranu amonného (iniciátor) a N,N'-methylen-bis-akrylamidu (síťovací činidlo). U hydrogelů byly stanoveny tepelné a fyzikálně-chemické vlastnosti za použití termogravimetrické analýzy a diferenciální skenovací kalorimetrie. Dále byl studován a optimalizován vlivy síťovacího činidla na bobtnací poměr (SR) a rozpustnost připravených hydrogelů. Nejvyšší SR byl stanoven ve vodě u nezesítěného hydrogelu připraveného s voskovým kukuřičným škrobem (780 g vody na g sušiny) a SR tohoto hydrogelu v roztocích síranu amonného byl 9,6 g na g sušiny a dusičnanu vápenatého byl 1,2 g na g sušiny. Vyšší tepelná stabilita je pozorována u zesítěných hydrogelů a naopak nezesíťované hydrogely měly sice vyšší SR, ale také větší rozpustnost ve vodě