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Peperomia fraseri , bract initiation and early development. A , B , Top view of apical meristem of main inflorescence (i.e., raceme of spikes), showing various ontogenetic stages of spike-subtending bracts. A , Nonfasciated inflorescence with 8 þ 13 contact parastiches. B , Fasciated inflorescence. C , Portion of a young raceme of spikes showing different stages of spike initiation and early development. Most spike- subtending bracts are removed to show spikes. D , Spike primordium before initiation of flower-subtending bract. E , First flower-subtending bracts initiated on spike apical meristem. F , Small portion of young raceme of spikes showing seven spikes at different developmental stages; spike- subtending bracts have been removed. G , Very young spike, abaxial view. Note flower-subtending bract primordia are suppressed in the lower abaxial side of the spike. BR 1⁄4 flower-subtending bract, SA 1⁄4 spike apex, SSB 1⁄4 spike-subtending bract. Scale bars: A , C 1⁄4 500 m m; B 1⁄4 1 mm; D 1⁄4 80 m m; E , G 1⁄4 60 m m; F 1⁄4 120 m m.
Source publication
Floral and inflorescence structure and ontogeny are described in detail in Peperomia fraseri, an anomalous species of Piperaceae that differs in several respects from other species of Peperomia and other perianthless Piperales (Piperaceae and Saururaceae). Inflorescence structure is atypical in this species, with numerous spikes arranged spirally o...
Contexts in source publication
Context 1
... Stems, spike-subtending and flower- subtending bracts, and gynoecia are all covered by small glandular hairs. The raceme axis also bears unicellular non- glandular simple hairs, though these are rare on spike peduncles. All organs, including the stamens, bear ethereal oil cells in the epidermis. Stomata were observed only on bracts. Inflorescence. The apical meristem of the raceme, if not fasciated, is 120–250 m m in diameter and dome shaped. The height of the meristem above the level of formation of the first primordia is about half its diameter at this level. The apical meristem produces spirally arranged spike-subtending bract primordia in an acropetal sequence. Spike-subtending bract primordia typically form 8 þ 13 contact parastichies (fig. 4 A ). The primordia are hemispherical and ca. 30 m m in diameter at initiation. They soon elongate in a transverse di- rection to become ellipsoidal. In fasciated racemes, the apical meristem is almost linear when viewed from above. It may be more than 1.5 mm long and 50–250 m m wide (the width is variable along the meristem length; fig. 4 B ). When the spike-subtending bract is ca. 100 m m long and 60 m m wide, a small (ca. 20 m m) hemispherical spike primordium is initiated in its axil (fig. 4 C , 4 D ). The first flower-subtending bract primordia (fig. 4 E ) are initiated when the spike primordium (now spike apical meristem) reaches 70–90 m m in diameter. At that point, the spike-subtending bract is ca. 600 m m long. The spike apical meristem is dome shaped when the first flower-subtending bract primordia are initiated on it but almost flat during its final stages of activity. At initiation, flower-subtending bract primordia are rounded in outline and 20–30 m m in diameter (fig. 4 F , 4 G ). They are initiated in a rapid sequence, rendering details difficult to discern. However, at least in some cases, the first two flower-subtending bract primordia are initiated in a transverse-abaxial position and the third one in an adaxial position. At later stages of spike development, the flower- subtending bracts are spirally arranged, with 5 þ 8 contact parastichies often recognizable. The peltate blade of the bract is formed first, and its stalk appears later, following interca- lary growth. Proximal, bisexual flowering region. Typically, primordia of bisexual flowers are initiated when flower-subtending bracts are already well differentiated. However, a few primordia of bisexual flowers are initiated in the axils of small undifferentiated bracts (fig. 5 B , 5 E ; fig. 6 A , 6 B ); in the mature spike, these bracts apparently remain smaller than the other bracts (e.g., reduced bract in fig. 6 D ). The lowermost abaxial flower and/or some other flowers can be initiated in the absence of their subtending bract (fig. 6 C ), or the bract can be represented by a scarcely visible bulge (fig. 6 E , 6 F ). Young primordia of bisexual flowers are ca. 30–40 m m 3 15–20 m m in size and are horseshoe shaped, the concavity denoting the abaxial side of the primordium (fig. 5 A , 5 B ; fig. 6 A ). When the floral primordium reaches 65–80 m m in width, two stamen primordia are initiated at each transverse- adaxial end (fig. 5 E ), followed by the gynoecium primordium in the center (fig. 5 C , 5 D , 5 F ). Stamen and gynoecium primordia are almost hemispherical at initiation. During early development, the gynoecium is much smaller than the stamens. The gynoecium develops as an ascidiate structure (fig. 8 D ). When it reaches ca. 60 m m, its ascidiate nature becomes apparent because of a small depression at the center. Growth of the meristematic ring around this depression soon closes the gynoecial opening so that ovule initiation is not visible without dissection. Distal, unisexual flowering region (figs. 7, 8). In the upper half of the spike (the female-flowered region), the lower flowers are initiated in the axils of their subtending bracts. Like the bisexual flowers in the proximal region of the spike, they are usually initiated when the bract is already quite large and differentiated as a peltate structure (fig. 7 A ). Sometimes the flower primordium deviates slightly to the right or left from the median plane of its subtending bract (fig. 8 A ). At initiation, the female flower primordium is typically ellipsoidal, being elongated in a transverse plane. Primordia of lower female flowers are intermediate between ellipsoidal and horseshoe shaped. The entire primordium produces the gynoecium, which develops in the same way as in bisexual flowers, though there is much variability in gynoecial shape. The uppermost female flowers usually are not subtended by bracts at initiation, or the bract is very small. We did not find examples of bract initiation after formation of flower primordia. There is no residual apex; at the top of the spike apical meristem, one or two abracteate female flowers are initiated that fill almost all the available space. Normally, no single female primordium occupies an exact terminal position on the spike apical meristem, but we observed a few cases of initiation of a female flower in a terminal position. The uppermost female flowers are delayed in initiation and development compared with other female flowers (fig. 8 B –8 F ). During development of the lowermost female flowers (i.e., those that are situated immediately distal to the bisexual flowers along the spike axis), one or two stamen primordia can be initiated (fig. 7 F ). These stamen primordia are then arrested in development and remain as small, undifferentiated structures during late developmental stages. They are not visible in mature ...
Context 2
... Stems, spike-subtending and flower- subtending bracts, and gynoecia are all covered by small glandular hairs. The raceme axis also bears unicellular non- glandular simple hairs, though these are rare on spike peduncles. All organs, including the stamens, bear ethereal oil cells in the epidermis. Stomata were observed only on bracts. Inflorescence. The apical meristem of the raceme, if not fasciated, is 120–250 m m in diameter and dome shaped. The height of the meristem above the level of formation of the first primordia is about half its diameter at this level. The apical meristem produces spirally arranged spike-subtending bract primordia in an acropetal sequence. Spike-subtending bract primordia typically form 8 þ 13 contact parastichies (fig. 4 A ). The primordia are hemispherical and ca. 30 m m in diameter at initiation. They soon elongate in a transverse di- rection to become ellipsoidal. In fasciated racemes, the apical meristem is almost linear when viewed from above. It may be more than 1.5 mm long and 50–250 m m wide (the width is variable along the meristem length; fig. 4 B ). When the spike-subtending bract is ca. 100 m m long and 60 m m wide, a small (ca. 20 m m) hemispherical spike primordium is initiated in its axil (fig. 4 C , 4 D ). The first flower-subtending bract primordia (fig. 4 E ) are initiated when the spike primordium (now spike apical meristem) reaches 70–90 m m in diameter. At that point, the spike-subtending bract is ca. 600 m m long. The spike apical meristem is dome shaped when the first flower-subtending bract primordia are initiated on it but almost flat during its final stages of activity. At initiation, flower-subtending bract primordia are rounded in outline and 20–30 m m in diameter (fig. 4 F , 4 G ). They are initiated in a rapid sequence, rendering details difficult to discern. However, at least in some cases, the first two flower-subtending bract primordia are initiated in a transverse-abaxial position and the third one in an adaxial position. At later stages of spike development, the flower- subtending bracts are spirally arranged, with 5 þ 8 contact parastichies often recognizable. The peltate blade of the bract is formed first, and its stalk appears later, following interca- lary growth. Proximal, bisexual flowering region. Typically, primordia of bisexual flowers are initiated when flower-subtending bracts are already well differentiated. However, a few primordia of bisexual flowers are initiated in the axils of small undifferentiated bracts (fig. 5 B , 5 E ; fig. 6 A , 6 B ); in the mature spike, these bracts apparently remain smaller than the other bracts (e.g., reduced bract in fig. 6 D ). The lowermost abaxial flower and/or some other flowers can be initiated in the absence of their subtending bract (fig. 6 C ), or the bract can be represented by a scarcely visible bulge (fig. 6 E , 6 F ). Young primordia of bisexual flowers are ca. 30–40 m m 3 15–20 m m in size and are horseshoe shaped, the concavity denoting the abaxial side of the primordium (fig. 5 A , 5 B ; fig. 6 A ). When the floral primordium reaches 65–80 m m in width, two stamen primordia are initiated at each transverse- adaxial end (fig. 5 E ), followed by the gynoecium primordium in the center (fig. 5 C , 5 D , 5 F ). Stamen and gynoecium primordia are almost hemispherical at initiation. During early development, the gynoecium is much smaller than the stamens. The gynoecium develops as an ascidiate structure (fig. 8 D ). When it reaches ca. 60 m m, its ascidiate nature becomes apparent because of a small depression at the center. Growth of the meristematic ring around this depression soon closes the gynoecial opening so that ovule initiation is not visible without dissection. Distal, unisexual flowering region (figs. 7, 8). In the upper half of the spike (the female-flowered region), the lower flowers are initiated in the axils of their subtending bracts. Like the bisexual flowers in the proximal region of the spike, they are usually initiated when the bract is already quite large and differentiated as a peltate structure (fig. 7 A ). Sometimes the flower primordium deviates slightly to the right or left from the median plane of its subtending bract (fig. 8 A ). At initiation, the female flower primordium is typically ellipsoidal, being elongated in a transverse plane. Primordia of lower female flowers are intermediate between ellipsoidal and horseshoe shaped. The entire primordium produces the gynoecium, which develops in the same way as in bisexual flowers, though there is much variability in gynoecial shape. The uppermost female flowers usually are not subtended by bracts at initiation, or the bract is very small. We did not find examples of bract initiation after formation of flower primordia. There is no residual apex; at the top of the spike apical meristem, one or two abracteate female flowers are initiated that fill almost all the available space. Normally, no single female primordium occupies an exact terminal position on the spike apical meristem, but we observed a few cases of initiation of a female flower in a terminal position. The uppermost female flowers are delayed in initiation and development compared with other female flowers (fig. 8 B –8 F ). During development of the lowermost female flowers (i.e., those that are situated immediately distal to the bisexual flowers along the spike axis), one or two stamen primordia can be initiated (fig. 7 F ). These stamen primordia are then arrested in development and remain as small, undifferentiated structures during late developmental stages. They are not visible in mature ...
Context 3
... Stems, spike-subtending and flower- subtending bracts, and gynoecia are all covered by small glandular hairs. The raceme axis also bears unicellular non- glandular simple hairs, though these are rare on spike peduncles. All organs, including the stamens, bear ethereal oil cells in the epidermis. Stomata were observed only on bracts. Inflorescence. The apical meristem of the raceme, if not fasciated, is 120–250 m m in diameter and dome shaped. The height of the meristem above the level of formation of the first primordia is about half its diameter at this level. The apical meristem produces spirally arranged spike-subtending bract primordia in an acropetal sequence. Spike-subtending bract primordia typically form 8 þ 13 contact parastichies (fig. 4 A ). The primordia are hemispherical and ca. 30 m m in diameter at initiation. They soon elongate in a transverse di- rection to become ellipsoidal. In fasciated racemes, the apical meristem is almost linear when viewed from above. It may be more than 1.5 mm long and 50–250 m m wide (the width is variable along the meristem length; fig. 4 B ). When the spike-subtending bract is ca. 100 m m long and 60 m m wide, a small (ca. 20 m m) hemispherical spike primordium is initiated in its axil (fig. 4 C , 4 D ). The first flower-subtending bract primordia (fig. 4 E ) are initiated when the spike primordium (now spike apical meristem) reaches 70–90 m m in diameter. At that point, the spike-subtending bract is ca. 600 m m long. The spike apical meristem is dome shaped when the first flower-subtending bract primordia are initiated on it but almost flat during its final stages of activity. At initiation, flower-subtending bract primordia are rounded in outline and 20–30 m m in diameter (fig. 4 F , 4 G ). They are initiated in a rapid sequence, rendering details difficult to discern. However, at least in some cases, the first two flower-subtending bract primordia are initiated in a transverse-abaxial position and the third one in an adaxial position. At later stages of spike development, the flower- subtending bracts are spirally arranged, with 5 þ 8 contact parastichies often recognizable. The peltate blade of the bract is formed first, and its stalk appears later, following interca- lary growth. Proximal, bisexual flowering region. Typically, primordia of bisexual flowers are initiated when flower-subtending bracts are already well differentiated. However, a few primordia of bisexual flowers are initiated in the axils of small undifferentiated bracts (fig. 5 B , 5 E ; fig. 6 A , 6 B ); in the mature spike, these bracts apparently remain smaller than the other bracts (e.g., reduced bract in fig. 6 D ). The lowermost abaxial flower and/or some other flowers can be initiated in the absence of their subtending bract (fig. 6 C ), or the bract can be represented by a scarcely visible bulge (fig. 6 E , 6 F ). Young primordia of bisexual flowers are ca. 30–40 m m 3 15–20 m m in size and are horseshoe shaped, the concavity denoting the abaxial side of the primordium (fig. 5 A , 5 B ; fig. 6 A ). When the floral primordium reaches 65–80 m m in width, two stamen primordia are initiated at each transverse- adaxial end (fig. 5 E ), followed by the gynoecium primordium in the center (fig. 5 C , 5 D , 5 F ). Stamen and gynoecium primordia are almost hemispherical at initiation. During early development, the gynoecium is much smaller than the stamens. The gynoecium develops as an ascidiate structure (fig. 8 D ). When it reaches ca. 60 m m, its ascidiate nature becomes apparent because of a small depression at the center. Growth of the meristematic ring around this depression soon closes the gynoecial opening so that ovule initiation is not visible without dissection. Distal, unisexual flowering region (figs. 7, 8). In the upper half of the spike (the female-flowered region), the lower flowers are initiated in the axils of their subtending bracts. Like the bisexual flowers in the proximal region of the spike, they are usually initiated when the bract is already quite large and differentiated as a peltate structure (fig. 7 A ). Sometimes the flower primordium deviates slightly to the right or left from the median plane of its subtending bract (fig. 8 A ). At initiation, the female flower primordium is typically ellipsoidal, being elongated in a transverse plane. Primordia of lower female flowers are intermediate between ellipsoidal and horseshoe shaped. The entire primordium produces the gynoecium, which develops in the same way as in bisexual flowers, though there is much variability in gynoecial shape. The uppermost female flowers usually are not subtended by bracts at initiation, or the bract is very small. We did not find examples of bract initiation after formation of flower primordia. There is no residual apex; at the top of the spike apical meristem, one or two abracteate female flowers are initiated that fill almost all the available space. Normally, no single female primordium occupies an exact terminal position on the spike apical meristem, but we observed a few cases of initiation of a female flower in a terminal position. The uppermost female flowers are delayed in initiation and development compared with other female flowers (fig. 8 B –8 F ). During development of the lowermost female flowers (i.e., those that are situated immediately distal to the bisexual flowers along the spike axis), one or two stamen primordia can be initiated (fig. 7 F ). These stamen primordia are then arrested in development and remain as small, undifferentiated structures during late developmental stages. They are not visible in mature ...
Context 4
... Stems, spike-subtending and flower- subtending bracts, and gynoecia are all covered by small glandular hairs. The raceme axis also bears unicellular non- glandular simple hairs, though these are rare on spike peduncles. All organs, including the stamens, bear ethereal oil cells in the epidermis. Stomata were observed only on bracts. Inflorescence. The apical meristem of the raceme, if not fasciated, is 120–250 m m in diameter and dome shaped. The height of the meristem above the level of formation of the first primordia is about half its diameter at this level. The apical meristem produces spirally arranged spike-subtending bract primordia in an acropetal sequence. Spike-subtending bract primordia typically form 8 þ 13 contact parastichies (fig. 4 A ). The primordia are hemispherical and ca. 30 m m in diameter at initiation. They soon elongate in a transverse di- rection to become ellipsoidal. In fasciated racemes, the apical meristem is almost linear when viewed from above. It may be more than 1.5 mm long and 50–250 m m wide (the width is variable along the meristem length; fig. 4 B ). When the spike-subtending bract is ca. 100 m m long and 60 m m wide, a small (ca. 20 m m) hemispherical spike primordium is initiated in its axil (fig. 4 C , 4 D ). The first flower-subtending bract primordia (fig. 4 E ) are initiated when the spike primordium (now spike apical meristem) reaches 70–90 m m in diameter. At that point, the spike-subtending bract is ca. 600 m m long. The spike apical meristem is dome shaped when the first flower-subtending bract primordia are initiated on it but almost flat during its final stages of activity. At initiation, flower-subtending bract primordia are rounded in outline and 20–30 m m in diameter (fig. 4 F , 4 G ). They are initiated in a rapid sequence, rendering details difficult to discern. However, at least in some cases, the first two flower-subtending bract primordia are initiated in a transverse-abaxial position and the third one in an adaxial position. At later stages of spike development, the flower- subtending bracts are spirally arranged, with 5 þ 8 contact parastichies often recognizable. The peltate blade of the bract is formed first, and its stalk appears later, following interca- lary growth. Proximal, bisexual flowering region. Typically, primordia of bisexual flowers are initiated when flower-subtending bracts are already well differentiated. However, a few primordia of bisexual flowers are initiated in the axils of small undifferentiated bracts (fig. 5 B , 5 E ; fig. 6 A , 6 B ); in the mature spike, these bracts apparently remain smaller than the other bracts (e.g., reduced bract in fig. 6 D ). The lowermost abaxial flower and/or some other flowers can be initiated in the absence of their subtending bract (fig. 6 C ), or the bract can be represented by a scarcely visible bulge (fig. 6 E , 6 F ). Young primordia of bisexual flowers are ca. 30–40 m m 3 15–20 m m in size and are horseshoe shaped, the concavity denoting the abaxial side of the primordium (fig. 5 A , 5 B ; fig. 6 A ). When the floral primordium reaches 65–80 m m in width, two stamen primordia are initiated at each transverse- adaxial end (fig. 5 E ), followed by the gynoecium primordium in the center (fig. 5 C , 5 D , 5 F ). Stamen and gynoecium primordia are almost hemispherical at initiation. During early development, the gynoecium is much smaller than the stamens. The gynoecium develops as an ascidiate structure (fig. 8 D ). When it reaches ca. 60 m m, its ascidiate nature becomes apparent because of a small depression at the center. Growth of the meristematic ring around this depression soon closes the gynoecial opening so that ovule initiation is not visible without dissection. Distal, unisexual flowering region (figs. 7, 8). In the upper half of the spike (the female-flowered region), the lower flowers are initiated in the axils of their subtending bracts. Like the bisexual flowers in the proximal region of the spike, they are usually initiated when the bract is already quite large and differentiated as a peltate structure (fig. 7 A ). Sometimes the flower primordium deviates slightly to the right or left from the median plane of its subtending bract (fig. 8 A ). At initiation, the female flower primordium is typically ellipsoidal, being elongated in a transverse plane. Primordia of lower female flowers are intermediate between ellipsoidal and horseshoe shaped. The entire primordium produces the gynoecium, which develops in the same way as in bisexual flowers, though there is much variability in gynoecial shape. The uppermost female flowers usually are not subtended by bracts at initiation, or the bract is very small. We did not find examples of bract initiation after formation of flower primordia. There is no residual apex; at the top of the spike apical meristem, one or two abracteate female flowers are initiated that fill almost all the available space. Normally, no single female primordium occupies an exact terminal position on the spike apical meristem, but we observed a few cases of initiation of a female flower in a terminal position. The uppermost female flowers are delayed in initiation and development compared with other female flowers (fig. 8 B –8 F ). During development of the lowermost female flowers (i.e., those that are situated immediately distal to the bisexual flowers along the spike axis), one or two stamen primordia can be initiated (fig. 7 F ). These stamen primordia are then arrested in development and remain as small, undifferentiated structures during late developmental stages. They are not visible in mature ...
Context 5
... Stems, spike-subtending and flower- subtending bracts, and gynoecia are all covered by small glandular hairs. The raceme axis also bears unicellular non- glandular simple hairs, though these are rare on spike peduncles. All organs, including the stamens, bear ethereal oil cells in the epidermis. Stomata were observed only on bracts. Inflorescence. The apical meristem of the raceme, if not fasciated, is 120–250 m m in diameter and dome shaped. The height of the meristem above the level of formation of the first primordia is about half its diameter at this level. The apical meristem produces spirally arranged spike-subtending bract primordia in an acropetal sequence. Spike-subtending bract primordia typically form 8 þ 13 contact parastichies (fig. 4 A ). The primordia are hemispherical and ca. 30 m m in diameter at initiation. They soon elongate in a transverse di- rection to become ellipsoidal. In fasciated racemes, the apical meristem is almost linear when viewed from above. It may be more than 1.5 mm long and 50–250 m m wide (the width is variable along the meristem length; fig. 4 B ). When the spike-subtending bract is ca. 100 m m long and 60 m m wide, a small (ca. 20 m m) hemispherical spike primordium is initiated in its axil (fig. 4 C , 4 D ). The first flower-subtending bract primordia (fig. 4 E ) are initiated when the spike primordium (now spike apical meristem) reaches 70–90 m m in diameter. At that point, the spike-subtending bract is ca. 600 m m long. The spike apical meristem is dome shaped when the first flower-subtending bract primordia are initiated on it but almost flat during its final stages of activity. At initiation, flower-subtending bract primordia are rounded in outline and 20–30 m m in diameter (fig. 4 F , 4 G ). They are initiated in a rapid sequence, rendering details difficult to discern. However, at least in some cases, the first two flower-subtending bract primordia are initiated in a transverse-abaxial position and the third one in an adaxial position. At later stages of spike development, the flower- subtending bracts are spirally arranged, with 5 þ 8 contact parastichies often recognizable. The peltate blade of the bract is formed first, and its stalk appears later, following interca- lary growth. Proximal, bisexual flowering region. Typically, primordia of bisexual flowers are initiated when flower-subtending bracts are already well differentiated. However, a few primordia of bisexual flowers are initiated in the axils of small undifferentiated bracts (fig. 5 B , 5 E ; fig. 6 A , 6 B ); in the mature spike, these bracts apparently remain smaller than the other bracts (e.g., reduced bract in fig. 6 D ). The lowermost abaxial flower and/or some other flowers can be initiated in the absence of their subtending bract (fig. 6 C ), or the bract can be represented by a scarcely visible bulge (fig. 6 E , 6 F ). Young primordia of bisexual flowers are ca. 30–40 m m 3 15–20 m m in size and are horseshoe shaped, the concavity denoting the abaxial side of the primordium (fig. 5 A , 5 B ; fig. 6 A ). When the floral primordium reaches 65–80 m m in width, two stamen primordia are initiated at each transverse- adaxial end (fig. 5 E ), followed by the gynoecium primordium in the center (fig. 5 C , 5 D , 5 F ). Stamen and gynoecium primordia are almost hemispherical at initiation. During early development, the gynoecium is much smaller than the stamens. The gynoecium develops as an ascidiate structure (fig. 8 D ). When it reaches ca. 60 m m, its ascidiate nature becomes apparent because of a small depression at the center. Growth of the meristematic ring around this depression soon closes the gynoecial opening so that ovule initiation is not visible without dissection. Distal, unisexual flowering region (figs. 7, 8). In the upper half of the spike (the female-flowered region), the lower flowers are initiated in the axils of their subtending bracts. Like the bisexual flowers in the proximal region of the spike, they are usually initiated when the bract is already quite large and differentiated as a peltate structure (fig. 7 A ). Sometimes the flower primordium deviates slightly to the right or left from the median plane of its subtending bract (fig. 8 A ). At initiation, the female flower primordium is typically ellipsoidal, being elongated in a transverse plane. Primordia of lower female flowers are intermediate between ellipsoidal and horseshoe shaped. The entire primordium produces the gynoecium, which develops in the same way as in bisexual flowers, though there is much variability in gynoecial shape. The uppermost female flowers usually are not subtended by bracts at initiation, or the bract is very small. We did not find examples of bract initiation after formation of flower primordia. There is no residual apex; at the top of the spike apical meristem, one or two abracteate female flowers are initiated that fill almost all the available space. Normally, no single female primordium occupies an exact terminal position on the spike apical meristem, but we observed a few cases of initiation of a female flower in a terminal position. The uppermost female flowers are delayed in initiation and development compared with other female flowers (fig. 8 B –8 F ). During development of the lowermost female flowers (i.e., those that are situated immediately distal to the bisexual flowers along the spike axis), one or two stamen primordia can be initiated (fig. 7 F ). These stamen primordia are then arrested in development and remain as small, undifferentiated structures during late developmental stages. They are not visible in mature ...
Citations
... 2 namely Aristolochiaceae, Piperaceae, and Saururaceae (The Angiosperm Phylogeny Group, 2016). It is interesting to note that the two perianth-less (lacking petals and/or sepals) families, Piperaceae and Saururaceae, exhibit marked dissimilarity when juxtaposed with the perianth-bearing family Aristolochiaceae (Jaramillo et al., 2004;Remizowa et al., 2005). Due to its perianth-less floral composition and easy artificial propagation, S. chinensis has primarily found utility in genetic investigations to understand the origin of primitive flowering plants (Zhao et al., 2013;Zhao et al., 2021;Xue et al., 2023). ...
Several months earlier, other researchers had achieved the inaugural publication of the Chinese Lizardtail Herb ( Saururus chinensis ) genome dataset. However, the quality of that genome dataset is not deeply satisfactory, especially in terms of genome continuity (Contig N50 length ≈ 1.429 Mb) and gene-set completeness (BUSCO evaluation ≈ 91.32%). In this study, we present an improved chromosome-level genome of S. chinensis , characterized by heightened genome continuity (Contig N50 length ≈ 4.180 Mb) and a more complete gene-set (BUSCO evaluation ≈ 95.91%). Our investigation reveal that the extant S . chinensis genome preserves abundant vestiges of a paleo-tetraploidization event that are discernible both at the macroscopic chromosome level and within microscopic gene families, such as the PEL (pseudo-etiolation in light) family. Moreover, we elucidate that this paleo-tetraploidization event is associated with an expansion of the PEL family, potentially initiating a process conducive to its neofunctionalization and/or subfunctionalization.
... U-shaped or horseshoe-shaped floral primordia are not unusual during floral morphogenesis. These are typically found during carpel development (Barabé and Lacroix, 2001;Chang and Sun, 2020) but also the entire floral primordium can have a horseshoe shape (Remizowa et al., 2005). Although flowers of F. graciliflora, V. locusta, and C. ruber possess five Bracts alternate with lateral petals in developing flower (J-K, bract develops over left lateral petal; L, bract develops over right lateral petal). ...
Valerianaceae provides a model clade for examining diversification in floral shape, especially involving size, bilateral symmetry, asymmetry, and handedness. Fedia species have pink, strongly bilaterally symmetrical corollas while Valerianella species generally have white, near-radially symmetrical corollas. In this study we examine the early floral ontogeny of Valerianella locusta and Fedia graciliflora to compare early growth and developmental traits that may lead to the difference in their mature flowers. Fedia graciliflora and V. locusta inflorescences at varying stages of development were collected and dissected to remove subtending bracts and bracteoles. Images of floral development were taken using a stereomicroscope and a Scanning Electron Microscope. The inflorescence primordium appears to continuously bifurcate as it grows, resulting in an inflorescence with densely packed flowers of varying ages. Flowers of both F. graciliflora and V. locusta initiate petals and stamens simultaneously on a ring-like common primordium. We demonstrate that stamen primordia arise in a spiral pattern, grow faster than other organs, and dominate growth until they are nearly mature. Five petal primordia and two stamens arise in F. graciliflora. In contrast, in V. locusta which has three stamens, four petal primordia initiate, which appear as an open ring-like or U-shaped primordium with a furrow on one side. This likely provides the space for the additional large stamen. Sepal development is not evident and lobes are lacking. Then gynoecium does not begin to develop until the flower bud is nearing maturity. These data provide a framework for future developmental genetic work in these species.
... In basal angiosperms (ANITA grade and magnoliids) there are some comparative studies at the family level including inflorescence structure (e.g., Chloranthaceae: Endress 1987a; Eklund et al. 2004;Hernandiaceae: Kubitzki 1969;Lauraceae: Mez 1889;Weberling 1985;Rohwer 1993a;Kurz 2000;Myristicaceae: de Wilde 1991;Aristolochiaceae: González 1999; Lactoridaceae: González and Rudall 2001;Piperaceae: Tucker 1982;Remizowa et al. 2005;Sokoloff et al. 2006;Saururaceae: Rohweder and Treu-Koehne 1971;Tucker 1981) and even a preliminary survey of "primitive" angiosperms (Weberling 1988). How-ever, the level in between-the order level-has not been focused on. ...
Premise of research. This is the first comparative study of inflorescence morphology through all seven families of the order Laurales (Atherospermataceae, Calycanthaceae, Gomortegaceae, Hernandiaceae, Lauraceae, Monimiaceae, and Siparunaceae) and the larger subclades of these families. Methodology. We studied 89 species of 39 genera from herbarium specimens and partly from liquid-fixed material, focusing on the branching patterns in the reproductive region. In addition, we used the information from the literature. Pivotal results. There are recurrent branching patterns. Botryoids, thyrsoids, and compound botryoids and thyrsoids are the most common forms. Panicles, racemes, and thyrses are rare. Panicles and racemes occur in some highly nested Lauraceae and thyrses in Hernandiaceae. Thus, the presence of thyrso-paniculate inflorescences is not characteristic for Laurales, in contrast to the statement by Weberling. Conclusions. An evolutionary interpretation is still difficult because the existing molecular phylogenetic analyses are not fine grained enough and also because the previous phylogenetic results are not robust enough to make firm conclusions within the order. However, the present structural results show that there are trends of occurrence of certain patterns in families or subclades within families, and these may be useful in a morphological matrix of magnoliids (see work by Doyle and Endress for basal angiosperms).
... Morphological interpretation and origin of the gynoecium of Peperomia (Piperaceae) are of considerable interest. This closed tubular structure either has no lobes on the edge or has two poorly developed lobes that emerge at late developmental stages; a single basal orthotropous ovule is located in the center of the gynoecium [97,98]. Phylogenetic data clearly demonstrate that this gynoecium is derived from a mixomerous gynoecium with a single basal ovule and several stigmas [99]. ...
The presence of a gynoecium composed of carpels is a key feature of angiosperms. The carpel is often regarded as a homologue of the gymnosperm megasporophyll (that is, an ovule-bearing leaf), but higher complexity of the morphological nature of carpel cannot be ruled out. Angiosperm carpels can fuse to form a syncarpous gynoecium. A syncarpous gynoecium usually includes a well-developed compitum, an area where the pollen tube transmitting tracts of individual carpels unite to enable the transition of pollen tubes from one carpel to another. This phenomenon is a precondition to the emergence of carpel dimorphism manifested as the absence of a functional stigma or fertile ovules in part of the carpels. Pseudomonomery, which is characterized by the presence of a fertile ovule (or ovules) in one carpel only, is a specific case of carpel dimorphism. A pseudomonomerous gynoecium usually has a single plane of symmetry and is likely to share certain features of the regulation of morphogenesis with the monosymmetric perianth and androecium. A genuine monomerous gynoecium consists of a single carpel. Syncarpous gynoecia can be abruptly transformed into monomerous gynoecia in the course of evolution or undergo sterilization and gradual reduction of some carpels. Partial or nearly complete loss of carpel individuality that precludes the assignment of an ovule (or ovules) to an individual carpel is observed in a specific group of gynoecia. We termed this phenomenon mixomery, since it should be distinguished from pseudomonomery.
... Представляют интерес морфологическая интерпретация и происхождение гинецея Peperomia (Piperaceae). Это замкнутая трубчатая структура без лопастей по краю или с двумя слабо выраженными и поздно возникающими лопастями, имеющая в центре одну базальную ортотропную семяпочку [97,98]. Филогенетические данные чётко указывают на происхождение этого гинецея из миксомерного с одной базальной семяпочкой и несколькими рыльцами [99]. ...
The presence of a gynoecium composed by carpels is a key feature of angiosperms. The carpel is often viewed as homologous to megasporophyll of gymnosperms (i.e., a leaf bearing ovules), but it is possible that its morphological nature is more complex. Carpels of angiosperms can unite to form a syncarpous gynoecium. Most syncarpous gynoecia possess a compitum, which is a region where pollen tube transmitting tracts of individual carpels unite in a way that pollen tubes can grow from one carpel to another. The presence of a compitum is a precondition for evolution of carpel dimorphism, where some carpels do not possess functional stigma or fertile ovules. Pseudomonomery is a kind of carpel dimorphism where only one carpel has a fertile ovule (or ovules). Pseudomonomerous gynoecium usually has a single symmetry plane and it is likely that regulation of its development is similar to those of monosymmetric perianth and androecium. Monomerous gynoecium consists of a single carpel. In course of evolution, syncarpous gynoecia can jump abruptly to monomerous gynoecia or undergo sterilization and gradual reduction of some carpels. There is a peculiar group of gynoecia with partial or complete loss of carpel individuality, so that it is impossible to assign an ovule (or ovules) to particular carpel. A term mixomery is proposed for this phenomenon, which is not identical to pseudomonomery.
... Prior to this, andromonoecy had not been recorded in Piperaceae. In Peperomia fraseri another unique sex distribution was found by Remizowa et al. (2005), here, the lower flowers of each spike are bisexual and the distal region of the same inflorescence bears pistillate flowers (gynomonoecy). The inflorescences of the species studied by Figueiredo & Sazima (2000) were creamy, yellowish or whitish in color, and most of them (except Piper aduncum) produced a sweet, lemon-like odor. ...
An updated description of the pollination and reproductive biology of basal angiosperms is given to
show their principal associations with pollinating agents. The review considers members of the
ANITA grade, as well as some basal monocots, the magnoliids, Chloranthaceae and Ceratophyllaceae.
Morphological, physiological and behavioral characteristics of flowers and their pollinating insects
are evaluated. Based on current evidence, early-divergent angiosperms were and are pollination generalists,
even so there has been early specialization for either flies, beetles, thrips or bees. Although
there are many tendencies for development from generalist flowers to specialist ones, there are also
reversals with the development from specialist flowers to generalist ones. The earliest specialization
seems to be fly pollination. Adaptations to more recently evolved insect groups, such as scarab beetles
or perfume-collecting euglossine bees, demonstrate that several basal angiosperm lines were flexible
enough to radiate into modern ecological niches.
... Thus, neither inflorescence nor flower is entirely satisfactory for defining the cyathium; both interpretations leave open issues such as the absence of distinct floral/organ primordia and the apparently hybrid nature of many structures. As with other strongly flowerlike inflorescences, notably those of Saururaceae and other perianthless Piperales (Remizowa et al., 2005), more than one possible scenario exists for the evolution of the Euphorbia cyathium (Fig. 9 ). It could be (1) derived from an Anthostemalike strongly condensed thyrse, terminated by a trimerous female flower, and spirally surrounded by dichasial male ...
The flower-like reproductive structure of Euphorbia s.l. (Euphorbiaceae) is widely believed to have evolved from an inflorescence, and is therefore interpreted as a special
type of pseudanthium, termed a cyathium. However, fuzzy morphological boundaries between the inflorescence, individual flowers,
and organs have fuelled the suggestion that the cyathium does not merely superficially resemble a flower but could actually
share developmental genetic pathways with a conventional flower. To test this hypothesis, immunolocalizations of FLORICAULA/LEAFY
(LFY), a protein associated with floral identity in many angiosperm species, were performed in developing cyathia of different
species of Euphorbia. Expression of the LFY protein was found not only in individual floral primordia (as predicted from results in the model
organisms Arabidopsis and Anthirrhinum), but also in the cyathium primordium and in the primordia of partial male inflorescences. These results provide further
evidence that the evolution of floral traits in pseudanthial inflorescences often involves expression of floral development
genes in the inflorescence apex. This finding blurs the conventional rigid distinction between flowers and inflorescences.
... Inflorescences in Piperales are mostly simple spikes, but an exception was described for the perianthless. Peperomia fraseri C.DC. has numerous spikes borne along a raceme (Remizova et al., 2005); it is, however, clearly distinct from Zlatkocarpus by having bisexual flowers proximally and pistillate flowers distally in the spikes, a high degree of polymorphism in the structure of bracts in the same inflorescence, and much denser secondary branching (Remizova et al., 2005). ...
... Inflorescences in Piperales are mostly simple spikes, but an exception was described for the perianthless. Peperomia fraseri C.DC. has numerous spikes borne along a raceme (Remizova et al., 2005); it is, however, clearly distinct from Zlatkocarpus by having bisexual flowers proximally and pistillate flowers distally in the spikes, a high degree of polymorphism in the structure of bracts in the same inflorescence, and much denser secondary branching (Remizova et al., 2005). ...
A new genus, Zlatkocarpus gen. nov., is described from the Peruc Korycany Formation (Cenomanian) of the Bohemian Cretaceous Basin in the Czech Republic based on inflorescence axis, fruits and pollen. Two species are assigned to the new genus, Zlatkocarpus brnikianus and Z. pragensis. Zlatkocarpus has a compound inflorescence consisting of primary axes bearing semi-decussately arranged spikes. Each spike has helically arranged unicarpellate and unilocular fruits. Each fruit apparently contains a single, orthotropous seed. The stigma is indistinct and sessile at the apex. The fruit wall has distinct globular protrusions (probable resin bodies). The fruits are supported at the base by a small floral cup and a bract. Pollen grains adhering to stigmatic areas and also on other surfaces of the fossil are monocolpate with a long colpus and an open reticulum. The pollen is similar to dispersed pollen broadly referred to the extinct pollen genus Retimonocolpites, but none of dispersed pollen genera are suitable for accommodating the fossils described here.
... Sokoloff, Rudall & Remizowa (2006) discussed the occurrence of atypical terminal flower-like structures (TFLS, equivalent to terminal peloria or terminal pseudanthia) in inflorescences that are otherwise indeterminate. These authors documented spontaneous TFLS in perianthless members of Piperales (see also Rohweder & Treu-Koene, 1971;Yamazaki, 1978;Tucker, 1981;Remizowa, Rudall & Sokoloff, 2005) and in some monocots, e. g. Acorus L. (Buzgo & Endress, 2000). ...
... Buzgo & Endress, 2000) and Piperales (e.g. Houttuynia cordata Thunb.; Rohweder & Treu-Koene, 1971;Yamazaki, 1978;Tucker, 1981; Peperomia fraseri C. DC.; Remizowa et al., 2005), a teratum-like terminal flower, the subterminal flowers and the corresponding bracts are progressively reduced or distorted. Contrary to the observed development in Gunnera, in Peperomia fraseri floral development retains an acropetal direction: the proximal floral apices become bisexual whereas the distal ones develop female flowers (Remizowa et al., 2005). ...
... Houttuynia cordata Thunb.; Rohweder & Treu-Koene, 1971;Yamazaki, 1978;Tucker, 1981; Peperomia fraseri C. DC.; Remizowa et al., 2005), a teratum-like terminal flower, the subterminal flowers and the corresponding bracts are progressively reduced or distorted. Contrary to the observed development in Gunnera, in Peperomia fraseri floral development retains an acropetal direction: the proximal floral apices become bisexual whereas the distal ones develop female flowers (Remizowa et al., 2005). Our observations in nine species of subgenus Panke strongly suggest that acropetal initiation of floral apices and basipetal development of flowers along each partial inflorescence (Fig. 8) are likely to be determined by independent (nonoverlapping) developmental programmes fixed in this subgenus. ...
A study of inflorescence and flower development in 12 species from four of the six subgenera of Gunnera (Gunneraceae) was carried out. In the species of subgenus Panke, initiation of floral apices along the partial inflorescences is acropetal but ends up in the late formation of a terminal flower, forming a cyme at maturity. The terminal flower is the largest and the most complete in terms of merosity and number of whorls and thus it is the most diagnostic in terms of species-level taxonomy. The lateral flowers undergo a basipetal gradient of organ reduction along the inflorescence, ranging from bisexual flowers (towards the distal region) to functionally (i.e. with staminodia) and structurally female flowers (towards the proximal region). Our results show that the terminal structure in Gunnera is a flower rather than a pseudanthium. The terminal flower is disymmetric, dimerous and bisexual, representing the common bauplan for Gunnera flowers. It has a differentiated perianth with two sepals and two alternate petals, the latter opposite the stamens and carpels. Comparisons with other members of the core eudicots with labile floral construction are addressed. We propose vegetative and floral putative synapomorphies for the sister-group relationship between Gunneraceae and Myrothamnaceae. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160, 262–283.
... Clearly, for an understanding of inflorescence development and evolution it is desirable to seek model organisms that possess such valuable architectural markers. Additionally, it is useful to compare them with anomalous species such as Peperomia fraseri (Piperaceae), in which both bracteate and abracteate flowers occur in different positions on the same inflorescence [42]. A comparative approach was adopted by Ho-Sung Yoon and David Baum [43] in their study of 'inflorescence-flowering' versus 'rosette-flowering' species of Brassicaceae, on the basis that rosette-flowering plants produce solitary flowers in the axils of rosette leaves (bracts), whereas inflorescenceflowering species lack bracts. ...
... Bracts and prophylls are not currently included in the ABC model of floral identity and its derivatives nor in models of inflorescence architecture. Peter Endress [39] tentatively concluded that they are not floral organs but highlighted the important morphogenetic and ecological functions of prophylls during early Opinion Trends in Plant Science Vol.14 No.6 floral development (see also [42,46,47]). In some floweringplant species, bracts and/or prophylls are petaloid. ...
Emerging evidence suggests that certain key genes control the branching patterns of flower-bearing axes (i.e. inflorescences) in angiosperms. However, the terminology surrounding inflorescence architecture is heavily typological and suffers from radically divergent definitions of terms that together reduce the value of some recent predictive models. We attempt to resolve the paradox of conflicting definitions of the same terms and clarify the assumptions surrounding this complex subject. We argue in favour of uniform terminology and against over-simplification. The valid conceptual platforms for modelling should be clearly defined and should adequately reflect observed structural diversity.
