Water relations and organic solutes production in four umbu tree (Spondias tuberosa) genotypes under intermittent drought

Abstract

In order to evaluate changes in leaf water potential (ψw) and solute accumulation induced by intermittent drought, an research was performed under greenhouse conditions using four umbu tree genotypes (GBU 44, GBU 48, GBU 50 and GBU 68) and two water treatments (control and stressed by withholding water), with four replicates. The ψw was measured in four-hour intervals during a 24-hour period at the first stomatal closure and at the end of the experimental period. Carbohydrates, amino acids, protein and proline contents were also evaluated in leaves and roots. Significant differences were found in most of the studied parameters. The lower ψw hour was between 800 h and 1200 h. GBU 50 reduced significantly ψw in stressed plants at 800 h, while control plants reduced at 1200 h . GBU 68 presented the higher ψw. The extending of the stress induced reductions to carbohydrates in the leaves of all genotypes, increases in amino acids to GBU 44 and 48, and reductions of 40% and 43% to GBU 50 and 68, respectively; results also showed alterations in proline content. In the roots, increases in carbohydrates were observed only in GBU 48. Alterations in amino acids, protein, and proline were verified. Umbu trees presented isohydric behavior maintaining high leaf water potential and a great variability in organic solutes accumulation in response to drought with marked differences among the genotypes.

Physiological limitations in two sugarcane varieties under water suppression and after recovering

“…Recent studies indicate that the main function of amino acid accumulation may be related to the osmotic adjustment (Sircelj et al 2005, Silva et al 2009, Medeiros et al 2012. In the present work, increases were observed in amino acid concentrations in the water suppression treatment, what may attest the function of osmoregulation and/or osmoprotection of these compounds.…”

“…The accumulation of osmoregulators in response to drought is an important mechanism for maintaining cell turgor, contributing to alleviate the reduction of the water potential. Previous studies have observed an increase in solutes in sugarcane and other species under water-deficient conditions (Ashraf and Foolad 2007, Cha-um e Kirdmanee 2009, Silva et al 2009, Silva et al 2013. Nevertheless, only solute accumulation does not favour the tolerance to drought per se, but the pathway that leads to the mechanism of drought tolerance is strongly influenced by this factor (Hasegawa et al 2000, Medeiros et al 2012.…”

“…In situations of water restriction, common physiological alterations include reduced leaf water potential and the relative water content (Nogueira et al 2000, Graça et al 2010, gas exchange, photosynthesis, as well as reduced maximum quantum efficiency of the photosystem II (Inman-Bamber and Smith 2005, Silva et al 2007, Jaleel et al 2009, Gonçalves et al 2010, Graça et al 2010. As a consequence, metabolic changes such as increase in osmoregulators (Nogueira et al 2001, Guimarães et al 2008, Silva et al 2009, Medeiros et al 2012) may occur along with significant alterations on the plant growth, in response to the lower turgor pressure in the cells (Hessini et al 2009). …”

Purification and characterization of a peroxidase present in xilopodium exsudates of umbu plants (Spondias tuberosa A.)

“…Under a temperature condition of 80°C, the activity of umbu POX is four times higher in crude exsudate then in the purified fraction. Since, xilopodium exsudates are rich in soluble sugars (Silva et al, 2009), is possible that these substances may be acting as a natural thermal protector for umbu POX. Other possibilities must be considered since for …”

“…The browning color atributed to this product may be related to oxidation of phenols by poliphenoloxidase or peroxidase, a common trouble viewed in food processing (Mousavizadeh and Sedaghathoor, 2011). Due to the formation of xylopodium and other characteristics, umbu plants are highly resistant to drought (Silva et al, 2009). A unique umbu tree is able to grow down into its roots near to two tons of xylopodium (Cavalcanti and Resende, 2006).…”