Impact of drying and cooling rate on the survival of the desiccation-sensitive wheat pollen

Abstract

Key message Fast-drying and cooling induce fast intracellular water loss and reduced ice-crystal formation, which may promote the formation of intracellular glasses that might improve the likelihood of wheat pollen survival. Abstract Long-term storage of pollen is important for the fertilization of spatially or temporally isolated female parents, especially in hybrid breeding. Wheat pollen is dehydration-sensitive and rapidly loses viability after shedding. To preserve wheat pollen, we hypothesized that fast-drying and cooling rates would increase the rate of intracellular water content (WC) removal, decrease intracellular ice-crystal formation, and increase viability after exposure to ultra-low temperatures. Therefore, we compared slow air-drying with fast-drying (dry air flow) and found significant correlations between pollen WC and viability (r = 0.92, P < 0.001); significant differences in WCs after specific drying times; and comparable viabilities after drying to specific WCs. Fast-drying to WCs at which ice melting events were not detected (ΔH = 0 J mg−1 DW, < 0.28 mg H2O mg−1 DW) reduced pollen viability to 1.2 ± 1.0%, but when drying to 0.39 mg H2O mg−1 DW, some viable pollen was detected (39.4 ± 17.9%). Fast cooling (150 °C min−1) of fast-dried pollen to 0.91 ± 0.11 mg H2O mg−1 DW induced less and a delay of ice-crystal formation during cryomicroscopic-video-recordings compared to slow cooling (1 °C min−1), but viability was low (4.5–6.1%) and comparable between cooling rates. Our data support that the combination of fast-drying and cooling rates may enable the survival of wheat pollen likely due to (1) a reduction of the time pollen would be exposed to drying-related deleterious biochemical changes and (2) an inhibition of intracellular ice-crystal formation, but additional research is needed to obtain higher pollen survival after cooling.

The metabolic profiles of Eugenia astringens and E. uniflora (Myrtaceae) sensitive seeds affect desiccation

“…E. astringens seeds reached their WC threshold three times faster than E. uniflora seeds (Figure 1a), and faster desiccations were proven to raise the likelihood of DS seed survival (Impe et al, 2022). So, while E. astringens present a lower desiccation sensitivity over E. uniflora seeds, the latter may rather have mechanical adaptations or chemical compounds to avoid fast desiccations as other DS species (Obroucheva and Antipova 2004, Xia et al, 2012).…”

Improving Ultra-Low Temperature Preservation Technologies of Soybean Pollen for Off-Season and Off-Site Hybridization

“…Besides dehydration, pollen viability can be affected by cooling speed, i.e., slow vs. fast cooling, during the preservation procedure (Dinato et al, 2020 ). A combination of fast-drying and cooling rates may enable the survival of pollen due to the reduction of the time of exposure to dehydration-related deleterious biochemical changes and the inhibition of intracellular ice-crystal formation (Impe et al, 2022 ). In this study, the 10 h-dehydrated pollen in the drying oven was suitable for all these three freezing and preservation methods, and the 8 h-dehydrated pollen in the drying oven was suitable for preservation in LN, and also suitable for freezing in LN and then preservation in a −80°C freezer ( Figure 5 ).…”

When Phased without Water: Biophysics of Cellular Desiccation, from Biomolecules to Condensates

“…Other organisms, even those able to withstand extreme desiccation, usually require that the loss of water occurs over a span of time in which they prime their biochemistry. 79,80 If such organisms dry too rapidly, they cannot survive the absence of water despite reaching vitrification. 32,81 The effects of vitrification on the kinetics of biomolecular processes in living systems are relatively poorly studied in the context of anhydrobiosis.…”

“…Many cells and organisms simply will not recover from desiccation, whether it occurs rapidly or gradually. Other organisms, even those able to withstand extreme desiccation, usually require that the loss of water occurs over a span of time in which they prime their biochemistry. , If such organisms dry too rapidly, they cannot survive the absence of water despite reaching vitrification. , …”