![]() We should note here that stomata in the basal parts mature once needles completely emerge from buds, which is typical for conifers, but the number of stomatal rows is set in the early stages of needle growth inside buds. The presence of stomata in phase B2 and the development of stomatal complexes in phase B3 indicate that the differentiation of stomata began after the initiation of longitudinal needle growth but before the needles emerged from the bud in the late B2 phase. In physiological and eco-physiological studies, this distributional pattern is often used and can be valuable also in the case of very young needles, especially when we consider that the morphological and anatomical development of needles and leaves is correlated with the physiological status of a plant. cembra were arranged in the same pattern as those in mature needles. The stomata present in phase B3 (when brachyblasts remained entirely enveloped by the parts constituting the sheath) in P. Stomata on growing pine needles in the B3 phase were described by Dvořák and Štokrová. In dormant winter buds, stomata are not visible on needle primordia, but they can be observed on young needles after they emerge from buds. The differentiation and development of stomatal complexes are closely tied to the need for gas exchange in growing needles. Most of the water absorbed from the soil is released through the stomata, and therefore, stomata closing and opening are strictly connected to a plant’s response to environmental factors. The stomata are anatomical gates that allow plants to take up CO 2, which is necessary for photosynthesis, while they retain a plant’s ability to control water loss by transpiration. In gymnosperms, stomatal complexes are arranged in rows, and the rows present an age gradient, which is a consequence of divisions of the intercalary meristem located in the basal part of a needle. Stomata emerge from the protodermal cells as a protoderm differentiates into the epidermis. Some of its cells, stomatal progenitor cells (meristemoid mother cells), produce a stomatal complex. Protoderm, which differentiates into the epidermis, covers the surface of needle primordium. Stomata differentiate from protodermal cells. In needles, the morphology of stomata is of special interest. Numerous, arranged in rows, visible Florin rings Numerous, arranged in rows, clearly visible Florin rings Numerous, big, pointed teeth covering needle tip Numerous, rounded in upper part, pointed on tip Morphological traits in chosen Pinus species in the B2 and B3 phases of bud development. These phenological stages were defined by him as follows: B0-dormant buds B1-buds are swollen B2-buds elongate and disjunction of bud scales makes the shoot surface visible B3-emergence of brachyblasts, which remain entirely enveloped by the parts constituting the sheath B4-emergence of needles and B5-disjunction of needles from the same fascicle. Debazac divided the process of growth into six phases, from B0 to B5, and proposed a classification consistent with bud morphology. During the expansion of long-shoot buds into mature shoots, some phenological stages can be distinguished. The length of a shoot is, to a large extent, determined by the number of short-shoot primordia initiated in the previous season, which are present in the bud. The growth of a shoot, defined as “predetermined” (buds contain all the primordia for the following season and, thus, the numbers of leaves and future lateral buds are already predetermined in the bud), can be completed in a relatively short time after dormancy breaking in spring. ![]() In a long-shoot bud, there are primordia of each structure of the future mature shoot. Short-shoot buds typically contain all the needle primordia formed in autumn before bud dormancy. Short shoots are covered by live cataphyll scales (typically 8–11), and the needle primordia of these shoots are tightly enclosed by them. To the best of our knowledge, this is the first study on the micromorphology of very young needles in representatives of the genus Pinus. These observations could be useful in pine systematics but also in palaeobotanical or physiological studies. strobus, Florin rings were also observed. In B3 for all the species, numerous stomata were visible. strobus, their size and density along the margin decreased basipetally. The teeth on the margin in all the species were pointed. strobus was the needle tip slightly rounded. In the B3 phase, needle tips were pointed. nigra) near the needle tips and were arranged in rows. Stomata became visible in the late B2 phase ( P. Teeth were also visible on the margins in P. In B2, needle tips were rounded or pointed, depending on the species. uncinata) were analyzed at phenological stages B2 and B3 (according to Debazac). Using a scanning electron microscope, the micromorphologies of needle primordia and the young needles of seven pine species ( Pinus cembra, P.
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