Effects of elevated CO₂ concentration and water deficit on fructan metabolism in Viguiera discolor Baker

Abstract

Elevated [CO2 ] is suggested to mitigate the negative effects of water stress in plants; however responses vary among species. Fructans are recognised as protective compounds against drought and other stresses, as well as having a role as reserve carbohydrates. We analysed the combined effects of elevated [CO2 ] and water deficit on fructan metabolism in the Cerrado species Viguiera discolor Baker. Plants were cultivated for 18 days in open-top chambers (OTC) under ambient (∼380 ppm), and high (∼760 ppm) [CO2 ]. In each OTC, plants were submitted to three treatments: (i) daily watering (control), (ii) withholding water (WS) for 18 days and (iii) re-watering (RW) on day 11. Analyses were performed at time 0 and days 5, 8, 11, 15 and 18. High [CO2 ] increased photosynthesis in control plants and increased water use efficiency in WS plants. The decline in soil water content was more distinct in WS 760 (WS under 760 ppm), although the leaf and tuberous root water status was similar to WS 380 plants (WS under 380 ppm). Regarding fructan active enzymes, 1-SST activity decreased in WS plants in both CO2 concentrations, a result consistent with the decline in photosynthesis and, consequently, in substrate availability. Under WS and both [CO2 ] treatments, 1-FFT and 1-FEH seemed to act in combination to generate osmotically active compounds and thus overcome water deficit. The proportion of hexoses to sucrose, 1-kestose and nystose (SKN) was higher in WS plants. In WS 760, this increase was higher than in WS 380, and was not accompanied by decreases in SKN at the beginning of the treatment, as observed in WS 380 plants. These results suggest that the higher [CO2 ] in the atmosphere contributed to maintain, for a longer period, the pool of hexoses and of low DP fructans, favouring the maintenance of the water status and plant survival under drought.

Influência da alta concentração atmosférica de CO2(↑[CO2]atm) × disponibilidade hídrica nas relações hídricas, trocas gasosas e acúmulo de carboidratos em Coffea arabica L.

“…As medições confirmam que a proporção de CO 2 , dentre os gases atmosféricos, aumentou globalmente de 280 ppm na era pré-industrial para 379 ppm em 2005 e, atualmente, já está em média 400 ppm (NOAA 2017). Este fato, associado ao potencial que as plantas possuem de assimilar carbono atmosférico por meio da fotossíntese e da produção de compostos de carbono, faz com que estudos sobre o crescimento, desenvolvimento e metabolismo de plantas sob elevadas concentrações de CO 2 recebam ampla atenção (Long & Bernarcchi 2003, Braga et al 2006, Kretzschmar et al 2009, Oliveira et al 2013.…”

Atmospheric CO2enrichment markedly increases photosynthesis and growth in a woody tropical bamboo from the Brazilian Atlantic Forest

“…Our data corroborate the results obtained by Gratani et al (2008), who showed that bamboo species have a high capacity to adjust their photosynthetic rates under severe environmental conditions. Current knowledge indicates that most tropical plants grow best under CO 2 enrichment (Aidar et al 2002;Souza et al 2008;Krorner 2009;Oliveira et al 2010Oliveira et al , 2012.…”

Fructan dynamics in the underground organs of Chresta exsucca (Asteraceae), a dry season flowering species

“…In general, water content of the sampled underground organs was lower than that reported for other species. For example, rhizophores of irrigated C. obovata plants had 85 % water content (Garcia et al 2011), while the tuberous roots of irrigated A. discolor had 80 % (Oliveira et al 2013). Dimorphic thickened roots of field-grown I. terminalis plants had 61-85 %, with the highest values being during the rainy season (Almeida et al 2017).…”