Consequences of early chilling stress in two Triticum species: plastic responses and adaptive significance

Abstract

Phenotypic plasticity of two primitive wheat species (Triticum monococcum L. and Triticum dicoccum S.) was studied in response to early chilling stress. Selection pressure differentials, gradients and plasticity costs on plant morphogenesis, growth and reserve carbohydrate consumption were estimated. Regression analysis was applied to investigate differential developmental changes and patterns between treatments. Four-day-old seedlings of T. monococcum and T. dicoccum, differing in plant stature and reserve carbohydrates, were given an early chilling temperature (4 °C for 42 day) and compared with control plants grown at 23 °C. Early chilling stress resulted in a significant increase in leaf mass ratio (LMR) and relative growth rate (RGR), a reduction in flag leaf size, total biomass, specific leaf area (SLA) and reserve carbohydrate storage at flowering, together with advanced onset of flowering. Selection pressure within the early chilling environment favoured early flowering, smaller SLA, higher LMR and lower reserve carbohydrates, suggesting the observed responses were adaptive. Furthermore, a regression of daily cumulative plant biomass derived from a crop growth simulation model (CERES-Wheat) on crop vegetation period revealed a divergent developmental pattern in early-chilled plants. Using selection pressure gradient analysis, we found similar responses among these traits, except for SLA and sucrose, indicating that these two traits have indirect effects on fitness. Thus, the total effects of SLA and reserve sucrose on relative fitness seem to be buffered via the rapid growth rate in chilled plants. While lower SLA may reduce early chilling stress effects at an individual leaf level, a higher LMR and use of reserve carbohydrates indicated that compensatory growth of chilled plants during the recovery period relied on the concerted action of altered resource allocation and reserve carbohydrate consumption. However, a significant cost of plasticity was evident only for flowering time, LMR and fructan levels in the early chilling environment. Our results demonstrate that morphological and intrinsic developmental (ontogenetic) patterns in two Triticum species respond to early chilling stress.

Spring Freeze Effect on Wheat Yield is Modulated by Winter Temperature Fluctuations: Evidence from Meta‐Analysis and Simulating Experiment

“…7a). Reductions in flag leaf size, total biomass, specific leaf area in wheat have been reported under chilling temperature (4°C) in climate chamber experiment (Valluru et al 2012). Such effects could have been attributed to the direct damage of low temperature on leaves and tissues (Theocharis et al 2012).…”

“…), which are associated with a lowered photosynthetic rate (Thakur and Nayyar ), a decrease in shoot biomass, flag leaf size and specific leaf area (Valluru et al. ), and altered carbohydrate metabolism (Theocharis et al. ).…”

“…However, the delayed freezing events in spring, so-called later spring freeze which are resulted from cold-current outbreaks occurring in most wheat production regions of China, could severely limit crop growth and cause considerable reduction of grain yield (Han et al 2013). The freeze stress-induced yield penalty is attributed mainly to reductions in spike number and spike length (Karimi et al 2011), which are associated with a lowered photosynthetic rate (Thakur and Nayyar 2013), a decrease in shoot biomass, flag leaf size and specific leaf area (Valluru et al 2012), and altered carbohydrate metabolism (Theocharis et al 2012).…”

Sequential abiotic stress applied to juvenile eggplant modifies the seedlings parameters, plant ontogeny and yield

“…The impact of these stressors was variable, but it confirmed the thesis that 'stress memory' and 'cross-tolerance' can be induced in eggplant following the application of stress factors in the early stages of development. Valluru et al (2012) specified morphological changes, i.e. a significant increase in leaf mass ratio, relative growth rate, a reduction in flag leaf size, total biomass and specific leaf area (SLA) as a result of early chilling of wheat.…”

“…As these pretreatments triggered an increase in both the fresh and dry weight of roots, it is likely that this enabled developing plants to utilise water and nutrients more effectively. A study by Valluru et al (2012) demonstrated that exposure to early chilling stress during the seedling stage in two Triticum species resulted in adaptive responses, including early flowering, and alterations in several morphological and functional traits. Martínez-Andújar et al (2011) treated tomato seedlings with osmotic stress to improve tolerance to drought and salinity after transplanting.…”