Growth, photosynthate partitioning and fructan accumulation in plants of Vernonia herbacea (Vell.) Rusby under two nitrogen levels

Abstract

The effect of two nitrogen concentrations on fructan accumulation and plant growth was analysed in plants of Vernonia herbacea during a year period. Plants of this species accumulate inulin-type fructans in the underground reserve organs (rhizophores). The plants were cultivated in glasshouse conditions and received weekly nutrient solutions containing 1.3 mmol.L -1 NO 3 -(Nlimited) or 10.7 mmol.L -1 NO 3 -(N-sufficient). Plants treated with N-sufficient solution presented an increase in total growth with higher biomass, more but smaller leaves resulting in higher total leaf area, higher net assimilation rate, specific leaf mass and higher biomass allocation to aerial organs. In addition, these plants presented higher contents of reducing sugars and lower fructan contents. In contrast, N-limited plants showed reduced total growth with lower biomass, higher biomass allocation to underground organs and higher fructan contents. Therefore, although N-limited plants presented a higher fructan concentration, the amount of fructan produced per plant was similar in both N treatments. Key words: Asteraceae, cerrado, fructans, underground reserve organs.Crescimento, partição de fotossintatos e acúmulo de frutanos em plantas de Vernonia herbacea (Vell.) Rusby tratadas com dois níveis de nitrogênio. O efeito de duas concentrações de nitrogênio sobre o acúmulo de frutanos e seu crescimento foi analisado durante um ano em plantas de Vernonia herbacea. As plantas foram cultivadas em casa de vegetação e receberam semanalmente solução nutritiva contendo 1,3 mmol.L -1 NO 3 -(N-limitado) ou 10,7 mmol.L -1 NO 3 -(N-suficiente). As plantas tratadas com a solução N-suficiente apresentaram maior crescimento, com maior biomassa, número maior de folhas, porém com menor área, resultando em área foliar total mais elevada, taxa de assimilação líquida e massa foliar específica mais altas, maior alocação de biomassa para os órgãos aéreos. Além disso, revelaram teores mais altos de açúcares redutores e mais baixos de frutanos. Já as plantas que receberam solução N-limitada apresentaram menor crescimento com menor biomassa, maior alocação de biomassa para os órgãos subterrâneos e maior conteúdo de frutanos. Portanto, embora as plantas sob Nlimitado tenham apresentado maior concentração de frutanos, sua produção por planta foi semelhante nos dois tratamentos de nitrogênio. Palavras-chave: Asteraceae, cerrado, frutanos, órgãos subterrâneos de reserva.

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

“…A long term study on growth of V. herbacea under both sufficient and limited nitrogen supply (Cuzzuol et al 2005b) showed that these plants present a low RGR potential, similar to plants native to poor soils (Lambers & Poorter 1992, Paulilo & Felippe 1995, Sassaki & Felippe 1998). According to their response to nutrient levels, the authors characterized V. herbacea as a Type I species, following the classification of Chapin (1980,1988) for wild species.…”

“…Rusby (Herbarium number: SP169567) were obtained and cultivated as described by Cuzzuol et al (2005b). Plants received, weekly, 100 mL of a specific nutrient solution containing 10.7 mmol L -1 N-NO 3 -, elaborated to supply adequate nitrogen required by V. herbacea as previously determined by Cuzzuol et al (2005a).…”

“…Therefore, the use of this N-limited concentration satisfies the criteria established for the study of a specific stress factor. A later study by Cuzzuol et al (2005b) reported that plants growing during one year under N-limited supply presented higher fructan contents in spite of a final reduced growth and lower rhizophore biomass, when compared to N-sufficient plants. Nevertheless, fructan production was very similar in both N-treatments at the end of the experimental period, due to the lower rhizophore biomass in the N-limited plants.…”

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

“…Volumes of 50 ml of nutrient solutions were applied, weekly, interspersed with distilled water as needed, to prevent desiccation of the plants. Every month, the substrates were watered with distilled water at a volume above saturation to promote the leaching of salts, thus avoiding salinization as described by Cuzzuol et al (2005a;.…”

“…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).…”