Table 1.
Tissue physical and biophysical heterogeneity: dry mass of whole embryo, cotyledon and axis, explants dimension, oil content and tissue lipid melt mid-points for the species studied.
Figure 1.
Desiccation sensitivity assessment for seeds and embryos.
Legend: Germination percentage of C. papaya, P. edulis and L. nobilis seeds desiccated to various moisture contents and germinated on water agar. Also shown is the in vitro germination (regrowth) of L. nobilis embryos, following desiccation to various moisture contents, on MS medium at 25±2°C with a 16 h light/dark photoperiod.
Figure 2.
Viability and regrowth of embryos following cryoprotection and cryopreservation.
Legend: Viability and regrowth of C. papaya (A, D, G, J), P. edulis (B, E, H, K) and L. nobilis (C, F, I, L) embryos/embryonic axes before (−LN) and after (+LN) cryopreservation using conventional (A–F) and vacuum infiltration (G–L) vitrification at 0°C. Data are means (± SE). Within species, means with the same letters are not significantly different (p<0.05) using Fisher’s pair wise comparison.
Figure 3.
DSC warming thermograms for C. papaya embryos following cryoprotection.
Legend: Representative DSC warming thermograms for C. papaya embryos untreated and treated with PVS2 under CV for 30, 60 and 90 min at 0°C showing ice melt (I), lipid melt (L), PVS2 melt (P) with melt enthalpies in brackets and PVS2 de-vitrification (Pdv). Samples were warmed from −100 to 25°C at 10°C min−1. Inset: Warming thermal profile of PVS2 solution with melt enthalpy in bracket (warming program: from −150 to 0°C at 10°C min−1).
Figure 4.
Embryos internal concentration of PVS2 and their corresponding regrowth.
Legend: Regrowth following cryopreservation compared to internal concentration of PVS2 (defined by melt enthalpy using a DSC) of C. papaya (A), P. edulis (B) and L. nobilis (C) embryos/embryonic axes with a polynomial fit. (○ = CV at 0°C; • = CV at 25°C; Δ = VIV at 0°C; ▴ = VIV at 25°C).
Figure 5.
DSC thermograms for dry seeds and embryos.
Legend: DSC warming thermograms for C. papaya (A), P. edulis (B) and L. nobilis (C) dry seeds and embryos/embryonic axes showing lipid melt endotherms. Samples were cooled from 25°C to −100°C and rewarmed to 25°C (50°C for L. nobilis) at ±10°C min−1. Numbers on each peak indicating different lipid melt peaks corresponding to peaks in Table 1.
Figure 6.
Legend: Mean time to germinate (MTG) based on embryo viability (elongation) compared to regrowth for C. papaya (A), P. edulis (B) and L. nobilis (C) showing relationship between seedling vigour and stress. (□ = control; ○ = CV at 0°C -LN; • = CV at 0°C +LN; Δ = CV at 25°C –LN; ▴ = CV at 25°C +LN; = VIV at 0°C -LN; ◊ = VIV at 0°C +LN;
= VIV at 25°C –LN;
= VIV at 25°C +LN). Numbers by each symbol represent: 1 = 30 min; 2 = 60 min; 3 = 90 min for CV; and 1 = 1 min; 2 = 2.5 min; 3 = 5 min for VIV respectively.