Growth and physiological response of two biomass sorghum (Sorghum bicolor (L.) Moench) genotypes bred for different environments, to contrasting levels of soil moisture

Abstract

A better understanding of plant mechanisms in response to drought is a strong premise to achieving high yields while saving unnecessary water. This is especially true in the case of biomass crops for non-food uses (energy, fibre and forage), grown with limited water supply. In this frame, we investigated growth and physiological response of two genotypes of biomass sorghum (<em>Sorghum bicolor</em> (L.) Moench) to contrasting levels of soil moisture in a pot experiment carried out in a greenhouse. Two water regimes (high and low water, corresponding to 70% and 30% field capacity) were applied to JS-2002 and Trudan-8 sorghum genotypes, respectively bred for dry sub-tropical and mild temperate conditions. Two harvests were carried out at 73 and 105 days after seeding. Physiological traits (transpiration, photosynthesis and stomatal conductance) were assessed in four dates during growth. Leaf water potential, its components and relative water content were determined at the two harvests. Low watering curbed plant height and aboveground biomass to a similar extent (ca. 􀀀70%) in both genotypes. JS-2002 exhibited a higher proportion of belowground to aboveground biomass, <em>i.e</em>., a morphology better suited to withstand drought. Despite this, JS-2002 was more affected by low water in terms of physiology: during the growing season, the average ratio in transpiration, photosynthesis and stomatal conductance between droughty and well watered plants was, respectively, 0.82, 0.80 and 0.79 in JS-2002; 1.05, 1.08 and 1.03 in Trudan-8. Hence Trudan-8 evidenced a ca. 20% advantage in the three traits. In addition, Trudan-8 could better exploit abundant moisture (70% field capacity), increasing aboveground biomass and water use efficiency. In both genotypes, drought led to very low levels of leaf water potential and relative water content, still supporting photosynthesis. Hence, both morphological and physiological characteristics of sorghum were involved in plant adaptation to drought, in accordance with previous results. Conversely, the common assumption that genotypes best performing under wet conditions are less suited to face drought was contradicted by the results of the two genotypes in our experiment. This discloses a potential to be further exploited in programmes of biomass utilization for various end uses, although further evidence at greenhouse and field level is needed to corroborate this finding.

Salt Tolerance and Na Allocation in Sorghum bicolor under Variable Soil and Water Salinity

“…The R:S decrease under salinity indicates plant reaction to reduce root exposure to the hostile environment. This is in contrast to drought stress that drives plants to expand their root system to explore a larger soil volume in search of water [59]. However, this hypothesis is not supported by the findings of Jafari et al [51], De Lacerda et al [60], and Al-Amoudi and Rashed [61], who reported a sorghum R:S increase at salinities up to 90, 100, and 240 mM NaCl, respectively, corresponding to 9, 10, and 24 dS m −1 of EC w .…”

Crop Factors Influencing Ethanol Production from Sorghum Juice and Bagasse

“…Increases in WUE DW under adequate vs. poor moisture have already been echoed in the literature [9,11,43], although in some works WUE DW peaked at medium-low watering, then decreased at high water supply [5,44]. This diverging behavior has already been remarked [43] as proof of the fact that sorghum can make the most efficient use of water when available moisture is at intermediate level.…”

“…This diverging behavior has already been remarked [43] as proof of the fact that sorghum can make the most efficient use of water when available moisture is at intermediate level.…”

“…In general, the wide intra-specific variation is exploited in breeding, in view of releasing genotypes at improved WUE. Studies on plant physiology help to detect genotypic differences in biomass sorghum [41][42][43], providing the grounds for the identification of valuable traits for breeding.…”

Drought Tolerance and Application of Marker-Assisted Selection in Sorghum

“…The morphological traits related to drought are one of the important aspects to look for when screening the promising sorghum lines for drought tolerance [ 12 ]. Morphological responses to drought in sorghum involve traits that are associated with drought tolerance, for instance, plant height, leaf arrangement, roots and root system, root to shoot ratio, and biomass [ 50 ]. Plants with large weight of root biomass production have a high chance to tolerate water stress [ 51 ].…”