Morphological Features and Biomass Partitioning of Lucerne Plants (Medicago sativa L.) Subjected to Water Stress

Abstract

Drought is one of the major abiotic stresses affecting the morphological, physiological, and metabolic processes of plants, and hence their growth and production on a global scale. Lucerne (Medicago sativa L.) is one of the most popular pasture species in semi-arid regions and plays a critical role in sustaining agricultural systems in many areas of the world. In order to evaluate the effect of water deficits on the growth and biomass distribution in different tissues of lucerne, plant height, leaf dry weight, leaf number and area, root dry weight, taproot length and lateral root number, and stem dry weight were measured at four stages from the seedling to flowering stages under three water regimes: (i) adequate water supply (minimum soil water content 85% pot capacity (PC)), (ii) moderate water stress (65% PC), and (iii) severe water stress (45% PC), imposed under a rainout shelter. With limited water supply, plant height, leaf number, leaf area and dry weight, taproot length, and total biomass were reduced, while lateral root numbers increased. The number of smaller leaves and root dry weight increased under moderate water stress, whereas severe water stress reduced them. Leaf, stem, and total dry weight were all reduced by the water deficits, but leaf dry weight was reduced the most and root dry weight the least, so there was a redistribution of biomass towards the roots, increasing the root–shoot ratio. These results help us to understand the response of lucerce to water stress and assist in developing a foundation for the sustainable use of lucerne in semi-arid agricultural systems.

Improved drought tolerance of EMS mutagenized Alfalfa (Medicago sativa L.) mutants by in vitro screening at germination stage

“…All mutants had better regrowth performances and tolerated drought stress conditions better than unirrigated control plant (Z2) on the given time intervals suggesting that decrease on photosynthesis and availability of photoassimilates under drought stress conditions limited in mutants compared to control plant (Table 1 ). Previous reports indicated that water stress reduced the number of leaves and leaf size and provided a lower biomass in alfalfa although the number of lateral branches increased particularly under severe drought conditions 25 which agreed with the corresponding results of this study (Table 1 ). The main reasons for the reduced plant leaf area under drought stress were shown the decreased leaf turgor pressure, canopy temperature, and availability of photoassimilates due to decrease of photosynthetic rate under drought stress conditions 26 .…”

Yield gaps of lucerne (Medicago sativa L.) in livestock systems of Argentina

“…Deficits in soil water availability cause a reduction in leaf size, which results in lower leaf area index (LAI). Luo, Li, Yan, Liu, and Turner (2020), found that lucerne crops subjected to a severe water stress (45% field capacity) had 60% lower leaf size than those kept at 85% soil water field capacity. Collino, Dardanelli, De Luca, and Racca (2005) evaluated the effects of irrigation in Manfredi (location 6) and found a 40% increase in yield for irrigated (20 t DM ha −1 yr −1 ) versus rainfed (14 t DM ha −1 yr −1 ) lucerne crops.…”

“…7 ± 2.1 t DM ha À1 yr À1 (approximately 65% gap). Deficits in soil water availability cause a reduction in leaf size, which results in lower leaf area index (LAI) Luo, Li, Yan, Liu, and Turner (2020),. found that lucerne crops subjected to a severe water stress (45% field capacity) had 60% lower leaf size than those kept at 85% soil water field capacity Collino, Dardanelli, De Luca, and Racca (2005).…”

APSIM‐Tropical Pasture model parameterization for simulating Marandu palisade grass growth and soil water in irrigated and rainfed cut‐and‐carry systems

“…Except for the crown mass and LAI, the estimates of the productive and biometric characteristics showed fewer errors for the irrigated system (Table 3). This can be caused by uncertainties in how partitioning between shoot and root of Marandu palisade grass are affected by water deficit, which is a common response of plants under water deficit (Luo et al, 2020). Then, experimental assessments of belowground growth and partitioning to this biomass pool should be conducted to solve these questions and improve the parameterisation.…”