Fructan production in Vernonia herbacea (Vell.) Rusby is related to adequate nitrogen supply and period of cultivation

Abstract

-(Fructan production in Vernonia herbacea (Vell.) Rusby is related to adequate nitrogen supply and period of cultivation). Previous studies showed that plants of Vernonia herbacea grown for one year under a limited nitrogen supply presented reduced growth and higher fructan content than plants treated with sufficient nitrogen supply. However, the total fructan production was similar in both plant groups due to the higher biomass of the underground reserve organ in nitrogensufficient (N-sufficient) plants. In the present study we aimed to evaluate if a stress growing condition under nitrogenlimited (N-limited) supply, following cultivation under N-sufficient supply would have a positive effect on fructan production. Plants cultivated during one year under N-sufficient supply (10.7 mmol L -1 N-NO 3 -) were separated in two groups. During the following six months, one group continued to receive the same treatment (control) while the other received an N-limited supply (1.3 mmol L -1 N-NO 3 -). Growth, photosynthesis and soluble carbohydrates were measured at days 0, 30, 60, 90 and 180. At day 30, plants transferred to N-limited supply showed a significant increase in growth and a decrease in fructan concentration, as a response to the stressing condition. However, in the following period growth was reduced and fructan concentration was increased, confirming the inverse relationship between nitrogen concentration and fructan content. After 180 days, although the fructan concentration in N-limited was significantly higher, with a fructan production of 6.0 g plant -1, the higher gain in rhizophore biomass after 18 months of cultivation in N-sufficient solution led to a fructan production of 8.3 g plant -1 , thus surpassing the higher fructan concentration of N-limited plants.Key words -"cerrado" vegetation, inulin, nutritional stress, plant growth, underground reserve organ RESUMO -(A produção de frutanos em Vernonia herbacea (Vell.) Rusby está relacionada com o suprimento adequado de nitrogênio e o tempo de cultivo). Estudos realizados anteriormente mostraram que plantas de Vernonia herbacea cultivadas durante um ano sob uma condição limitante de nitrogênio tiveram seu crescimento reduzido e apresentaram maiores teores de frutanos em comparação a plantas que receberam suprimento adequado de nitrogênio. Entretanto, a produção total de frutanos foi similar nos dois grupos de plantas devido à maior biomassa dos órgãos subterrâneos de reserva das plantas N-suficientes. O objetivo do presente estudo foi avaliar se o cultivo sob uma condição adequada de nitrogênio, que promove o crescimento das plantas, seguido de uma condição estressante de crescimento imposta por suprimento limitante de nitrogênio, promoveria a produção de frutanos. As plantas receberam durante um ano solução N-suficiente (10,7 mmol L -1 N-NO 3 -). Nos seis meses subseqüentes, metade das plantas passou a receber solução N-limitante (1,3 mmol L -1 N-NO 3 -), permanecendo as demais no tratamento N-suficiente. O crescimento, a fotossíntese e os carb...

Effects that nutritional and saline gradients have on the growth of Passiflora mucronata Lam. and Canavalia rosea (Sw.) DC. found in the restinga of Brazil

“…Some symptoms of nutritional and saline stress are quite similar. Such symptoms include a reduction in biomass and in the percentage of survival of the plants (Benlloch-González et al 2005), as well as lower growth rates (Chen et al 2003;Cuzzuol et al 2005a), low foliar succulence, higher root/shoot ratio (R:SR, Garg & Singla 2004;Cambraia 2005) and a reduction in photosynthetic activity (Lee et al 2004;Cuzzuol et al 2008).…”