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Role of water percolation in reproductive physiology of hazelnut (Corylus spp.)

Murali-Mohan Ayyanath, Mukund R. Shukla, Praveen K. Saxena
Environmental and experimental botany 2021 v.182 pp. 104278
Corylus, abiotic stress, apical dominance, biomarkers, branches, buds, catkins, cold tolerance, cultivars, dehiscence, endpoints, female flowers, flowering, growers, hazelnuts, horticulture, melatonin, mulches, occurrence, phenology, plastics, probability, rain, rhizosphere, sampling, serotonin, snow, snowmelt, snowpack, spring, temperature, thermoregulation, trees, tryptophan, water, winter
Hazelnut (Corylus spp.) flowering occurs during late winters and early spring which coincides with erratic fluctuating weather patterns. Irregular and reduced precipitation, especially in the form of snow, is assumed to dictate poor flowering and enhanced injury to catkins, especially in the sourced cultivars of interest to growers. We investigated the effect of water (precipitation received as rain and or snow) percolation during snowmelt period using phenological endpoints such as female flower ratio, bud position of female flower occurrence, and catkin dehiscence in sourced and locally adapted cultivars. These reproductive events were also analyzed for biochemical endpoints such as the concentrations of tryptophan, serotonin and melatonin in temporally collected bud or catkin samples. In addition, the yield responses of the tagged twigs were tracked and analyzed. When snow was consistently removed from the root zone (NS) or when a prior placed plastic sheet (P) disallowed water percolation, the percentage of female flowers and apical dominance declined in the sourced cultivars suggesting an erratic gradient between aerial and belowground temperature. The presence of snow cover resulted in increased probability of female flowers from dormant buds in sourced cultivars. Tryptophan was found to accumulate in the dormant buds of sourced cultivars where snow was not disturbed, while serotonin concentrations were significantly higher in NS and P treatments. Melatonin concentrations were notably high in dormant flower and vegetative buds of locally adapted cultivars especially subjected to P treatment. The biochemical markers may not only assist in identifying cold tolerance but also reveal abiotic stress negating responses modulated by relative concentrations of these molecules. Our results demonstrate that ideal conditions of good precipitation, especially as snow, would not only blanket to provide thermoregulation but also maintain the sensitive gradient on which temperate trees rely to break dormancy and initiate flower development. These findings also suggest that the use of horticultural alternatives such as thermal mulch could be an option for mitigating adverse conditions of reduced water percolation which affect reproductive physiology of hazelnut.