The use of network analysis to uncover homeostatic responses of a drought-tolerant sugarcane cultivar under severe water deficit and phosphorus supply

Abstract

The objective of this study was to identify how changes in the photosynthetic network would be linked to the homeostasis modulation of a drought tolerant sugarcane cultivar subjected to severe water deficit. Moreover, we tested the potential effect of phosphorus supply on the plant physiological responses to drought, because such element is essential to photosynthetic processes. This study was carried out in a greenhouse, where sugarcane plants (Saccharum spp.) cv. RB 86-7515 were grown. One singlenode stalk segment was planted in plastic pots (20 L) filled with soil (red-yellow ultisol). Soil fertilization was performed according to the chemical analysis, except for the phosphorus (P) supply. Plants were subjected to the original P concentration in soil (36 mg dm -3 ) or supplied with 50 mg P2O 5 dm -3 using CaH 4 (PO 4 ) 2 . Plants were irrigated daily until the beginning of drought treatment. After 90 days of shoot emergence, the water deficit was started at the phenological phase II (tillering). Plants were irrigated with the equivalent to 100% (control) or 10% (water deficit) of daily water requirement based on the evapotranspiration. Light response curves of leaf gas exchange and other physiological and growth variables were performed in each treatment. Data were subjected to analysis of variance and the mean values were compared by Tukey's test (p \ 0.05). To assess changes in system network, we evaluated the occurrence of photosynthetic system modulation under distinct water regimes and phosphorus supplying via the concept and measurement of global connectance, C g . Set of results from coefficient of variation (CV) and C g analyses indicated adjustments in the relationships among the elements of the leaf gas exchange network that support the high drought tolerance of the sugarcane cultivar RB 86-7515 and such adjustments enabled the homeostasis of both photosynthesis and plant growth under water deficit. Moreover, P supply improved the sugarcane acclimation capacity by affecting plant characteristics related to water status and photosynthetic performance and causing network modulation under water deficit.

Effects of phosphorus application on photosynthetic carbon and nitrogen metabolism, water use efficiency and growth of dwarf bamboo ( Fargesia rufa ) subjected to water deficit

“…In our study, the curling of dwarf bamboo leaves was observed when water stress decreased the LRWC. Several studies have shown that P fertilization can directly enhance LRWC, as well as free and bound water components in water-stressed plants (Singh et al, 2006a;Sato et al, 2010). However, P application had minimal effect on LRWC of dwarf bamboo, regardless of water availability (Table 2), as also shown in previous studies of other crop species Singh et al, 2006b;Burman et al, 2009).…”

“…Statistics as in 2.72 ± 0.08 b 2.63 ± 0.06 b 3.00 ± 0.10 a 2.70 ± 0.04 a* Proline (mg g À1 DW) 0.41 ± 0.13 b 0.40 ± 0.10 b 1.88 ± 0.17 a 1.28 ± 0.10 a* confirmed in several plants (dos Santos et al, 2004;Garg et al, 2004;Burman et al, 2009;Sato et al, 2010). Meanwhile, some other reasons may have contributed to the improvement of P n after P application, including increased ATP and NADPH productions, activated enzyme activities in Calvin cycle, enhanced regeneration of sugar phosphate, higher output rate of photosynthates and cell proliferation (Rao and Terry, 1995).…”

“…Soil water deficit is the most common environmental stress factor limiting the growth, development, productivity and regeneration of plants worldwide (Liu et al, 2014). Within a certain threshold of soil water stress, most plants are able to express several stress-related genes, which lead to a series of remarkable changes in morphological and physio-biochemical traits to resist or adapt to adverse environments (Lawlor and Cornic, 2002;Sato et al, 2010). However, these changes may vary greatly depending on the plant species, stress duration and intensity, as well as soil conditions (Reddy et al, 2004).…”

Biomass and bioenergy partitioning of sugarcane plants under water deficit

“…& G. M. Souza gumaia.gms@gmail.com deficit is associated with a decrease in leaf gas exchange (Inman-Bamber and Smith 2005;Smit and Singels 2006;Sato et al 2010). Initially, stomatal conductance decreases; however, the internal CO 2 concentration remains unchanged due to CO 2 concentrating mechanisms of C4 plants (Saliendra et al 1996;Ripley et al 2007).…”

Grain Yield, Dry Weight and Phosphorus Accumulation and Translocation in Two Rice (Oryza sativa L.) Varieties as Affected by Salt-Alkali and Phosphorus

“…Elgharably [23] found that 60 mg kg −1 P significantly increased wheat biomass and P accumulation under salt stress by reducing the Cl − and Na + uptake in the root and increasing root biomass. P fertilizer promoted sucrose accumulation in the plant by effectively improving cellular water status and photosynthetic stability [47]. P can promote water and nutritional uptake by accelerating root growth, increasing the root/shoot ratio, secreting organic acids and other mechanisms [48,49].…”