Table 1.
List of Gesneriaceae species used in this study and GenBank accession numbers for their ribosomal internal transcribed spacer 1 (ITS1) sequences.
Figure 1.
Leaf discoloration and injury severity of saintpaulia.
(A) Leaf color change of saintpaulia before (left) and 24 hours after (right) a rapid temperature decrease from 25°C to 5°C. Scale bar = 2 cm. (B) Severity of leaf injury after rapid temperature decrease of leaves initially kept at 30°C (squares), 25°C (circles), and 20°C (triangles). (C) Severity of injury when leaves pre-incubated at 30°C (closed circles) or 20°C (open circles) for 5, 10, 20, 30, 60 min were rapidly adjusted to 10°C. The points and associated bars in (B) and (C) indicate mean severity and standard error (n = 5).
Figure 2.
Changes in chlorophyll fluorescence during injury in saintpaulia leaf.
Solid lines show quantum yield of PS II (øII; closed circles) and non-photochemical quenching (NPQ; open circles), while broken lines indicate leaf temperature. These indices were measured during a rapid temperature decrease from 25°C to 15°C followed by rewarming to 25°C (A), during a gradual decrease from 25°C to 5°C (B), during a rapid decrease from 25°C to 5°C and kept at 5°C for 300 s followed by rewarming to 25°C (C), and during a rapid decrease from 25°C to 5°C and kept at 5°C for 30 s followed by rewarming to 25°C (D).
Figure 3.
Chlorophyll fluorescence of chloroplasts isolated from palisade mesophyll cells of saintpaulia leaf.
Quantum yield of PSII (øII) and non-photochemical quenching (NPQ) of isolated chloroplasts estimated from changes in chlorophyll fluorescence. Solid lines show øII (closed circles) and NPQ (open circles), while broken lines show temperature. These indices were measured at 25°C (A), and during a rapid decrease from 25°C to 5°C and kept at 5°C for 300 s followed by rewarming to 25°C (B).
Figure 4.
Cytosolic pH changes in palisade mesophyll, spongy mesophyll, and epidermal cells of saintpaulia leaf.
(A) Palisade mesophyll, spongy mesophyll, and upper and lower epidermal cells stained with BCECF-AM. BCECF-AM (green) and chlorophyll fluorescence (magenta) were observed before, immediately after (0 min), and 10 min after the temperature was decreased from 25°C to 5°C and kept at 5°C for 1 min. Scale bar = 40 µm. (B) Relative changes of BCECF-AM fluorescence intensity after a temperature decrease. The points and associated bars indicate mean intensity and standard error (n = 3).
Figure 5.
Effects of surrounding pH on isolated chloroplasts.
Fluorescent microscopic images of chloroplasts isolated from saintpaulia leaf suspended in buffer solution at pH 7.6 (left), pH 6.0 (middle), and pH 5.2 (right). Scale bar = 50 µm.
Figure 6.
Vacuolar dynamics after a rapid temperature decrease.
Vacuolar membrane labeled with FM1-43 (green) and chlorophyll fluorescence (magenta) in palisade mesophyll cells of saintpaulia leaf were observed before (A) and 10 min after (B) a rapid temperature decrease from 25°C to 5°C and kept at 5°C for 1 min. Scale bar = 20 µm. FM1-43 and chlorophyll fluorescence in spongy mesophyll cells observed before (C) and after (D) a rapid temperature decrease from 25°C to 5°C. Scale bar = 40 µm.
Figure 7.
Leaf discoloration and injury severity of Gesneriaceae plants.
(A) Discolored leaves of 10 Gesneriaceae plants after a rapid temperature decrease from 30°C to 10°C. (B) Severity of leaf injury in Columnea sp. (squares), Kohleria warszewiczii (circles), and Streptocarpus saxorum (triangles) after a rapid temperature decrease. Leaves initially kept at 30°C to 15°C were rapidly adjusted to 10°C. The points and associated bars indicate mean severity and standard error (n = 3). (C) Cross sections of intact or discolored leaves of 10 Gesneriaceae plants. From left to right: whole leaf sections of intact leaves, magnified view of palisade mesophyll cells of intact leaves, whole leaf sections of discolored leaves, and magnified view of palisade mesophyll cells of discolored leaves. Scale bars = 200 µm in whole-leaf images and 100 µm in magnified palisade mesophyll images.
Figure 8.
Cytosolic pH changes in palisade mesophyll cells of Gesneriaceae plants.
Cytosolic pH changes in palisade mesophyll cell of sensitive species (Columnea sp. and Kohleria warszewiczii) and insensitive species (Sinningia speciosa and Streptocarpus sp.) induced by a rapid temperature decrease. (A) Palisade mesophyll cells of Columnea sp. and Kohleria warszewiczii stained with pH-sensitive fluorescent dye, BCECF-AM. (B) Relative changes of BCECF-AM fluorescence intensity in palisade mesophyll cell of C. sp. and K. warszewiczii. (C) Palisade mesophyll cells of Sinningia speciosa and Streptocarpus sp. stained with BCECF-AM. (D) Relative changes of BCECF-AM fluorescence intensity in palisade mesophyll cell of S. speciosa and S. sp. Images in (A) and (C) were taken before, immediately after (0 min), and 10 min after a temperature decrease from 30°C to 10°C and kept at 10°C for 1 min. Scale bar = 40 µm. The points and associated bars in (B) and (D) indicate mean intensity and standard error (n = 3).