A comparative developmental study of flowers was carried out using epi-illumination light microscopy on four genera of Lamiaceae (Nepeta, Rosmarinus, Salvia, and Ziziphora), representing all three subtribes of Mentheae. All species examined share unidirectional (adaxial to abaxial) sepal initiation, except Rosmarinus, which has the reverse unidirectional sequence, starting abaxially. Initiated but suppressed bracteoles were detected only in Rosmarinus. In Rosmarinus, Salvia, and Ziziphora, initiation of petals and stamens proceeds unidirectionally from the abaxial side. Floral initiation of Nepeta has bidirectional inception of petals and unidirectional stamen initiation from the adaxial side. Temporal overlap in organ initiation between petal and stamen whorls occurs in all taxa, though this feature is more prominent in Rosmarinus. Significant structural and developmental features that distinguish the four genera include: (1) polysymmetric calyx tube, highly tomentose corolla and deeply four-partitioned ovary in Nepeta; (2) monosymmetric two-lipped calyx and shallowly four-partitioned ovary in Ziziphora; and (3) suppression of adaxial stamens in Salvia and Rosmarinus. Adaxial stamens are absent from Rosmarinus, but reduced stamens remain as staminodia in Salvia. In a phylogenetic context, the late monosymmetry of Nepeta and very early monosymmetry of Rosmarinus could both be regarded as derived conditions compared with the early monosymmetry of Salvia and Ziziphora.
One of the greatest challenges in ecology is to understand and predict the functional outcome of interaction networks. Size‐matching between plants and pollinators is one of the key functional traits expected to play a major role in structuring plant–pollinator interactions. However, the community‐wide patterns of size‐matching remain largely unexplored.
We studied the association between the degree of size‐matching and foraging efficiency, pollination efficiency and the probability of pairwise interactions in a community of Lamiaceae.
Our study revealed that foraging efficiency is maximal when bee proboscis length corresponds to the corolla tube depth of the flower visited. Pollination efficiency was maximal when the bee body height corresponds to the corolla width of the flower visited. While the degree of size‐matching did not influence the probability of interaction, it significantly influenced the strength of the interaction in terms of visitation frequency.
We suggest a size‐matching index as a reliable metric to predict the frequency of interactions as well as the effectiveness of visits in terms of foraging efficiency and pollination efficiency.
A comparative study of floral ontogeny in single- and double-flowered Alcea rosea L. was conducted using epi-illumination light microscopy. In both floral types, floral differentiation starts with the appearance of three epicalyx lobes, which subsequently subdivide to produce a 7–10-parted epicalyx. Five sepals appear then in a unidirectional or possibly spiral sequence. In single flowers, a corolla-androecium common primordium is formed and subsequently differentiated into five androecial sectors (= primary androecial primordia). Petals are developed at the base of the androecial sectors and secondary androecial primordia are initiated centrifugally in two rows on each sector. Later, tertiary androecial primordia are formed by the subdivision of secondary androecial primordia, which then differentiate into androecial units. Three types of double flowers were identified regarding androecial development. The first type of double flowers shows a more or less disorganised nature. However, 10 proliferation zones can be indentified in the proximal and distal tips of the androecial sectors. In the second and third types of double flowers, androecial development follows similar developmental pathways to that of single flowers. However, in second-type double flowers, the secondary androecial primordia differentiate into petals and the stamens then develop from the free space between the two rows of secondary androecial primordia. In third-type double flowers, after complete primordial partitioning, some primordia on the marginal parts of each androecial sector develop into petaloids or intermediate appendages. The gynoecium appears similarly in both floral types as numerous congenitally united carpel primordia. The double-flowered phenotypes of Alcea appear to fit the criteria for homoheterotopy with complete or partial replacement of stamens with petals, as well as for neoheterotopy, with the formation of stamens in a new position. Based on mutant phenotypes, it is suggested that different functions possibly contribute to the proliferation and differentiation of common primordia.
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