The Botanical Review

Rockhouses are semicircular recesses extending far back under cliff overhangs that are large enough to provide shelter for humans. The largest sandstone rockhouses in the eastern United States are at the heads of gorges, and they are in stream valleys cut during the Pleistocene; most are formed in Mississippian and Pennsylvanian-age rocks. Compared to the surrounding environment, the interior of rockhouses is shaded, is warmer during winter and cooler during summer, and has lower evaporation rates and higher humidities. Water enters rockhouses primarily by groundwater seepage and by dripping from the ceiling. Soil consists mostly of sand with low pH, but high levels of some nutrients are associated with saltpeter earth and with ecofactual and artifactual remains left by human occupants during prehistoric time. Most plant taxa in sandstone rockhouses in eastern United States are native C3 phanerophytes or hemicryptophytes, and similarities in species composition among rockhouses are low. Eleven plant taxa belonging to eight families of flowering plants and ferns are endemic or nearly endemic to sandstone rockhouses in eastern United States. Three endemics are restricted to the gorges of a single river, and only one taxon ranges far north of the Wisconsinan Glacial Boundary. The endemic ferns are Tertiary relicts derived from tropical taxa. The majority of endemic flowering plants are derived from temperate taxa that grow in habitats in the vicinity of rockhouses; their relative age ranges from Late Tertiary to the Recent. All the endemic taxa are perennial; two ferns occur as independent gametophytes. The endemic taxa of rockhouses are threatened primarily by disturbances associated with recreation.

Vegetative regeneration provides for immediate tissue replacement and reestablishment of the “parent” genotype, after the aerial canopy of a perennial plant is partially or wholly destroyed. If the frequency of destruction of above-ground biomass (e.g., by fire) is such that tissue replacement (production) is the predominant mode of growth, this regenerative capacity may preadapt the plant for reproduction via vegetative growth. In the perennial shrubs of the California chaparral, and in other similar Mediterranean-type ecosystems, one of the most significant modes of reproduction is characterized by sprouting after injury of new stem or root tissue from an ontogenetically produced swollen stem base/root crown known as a lignotuber (or “burl”). Lignotubers have been well described inEucalyptus (Myrtaceae) and observed in other families in the Mediterranean-type climate regions. “Burls” of shrubs in the family Ericaceae are morphologically similar to lignotubers. The term “burl” is vague in meaning, since it has been used to describe any anomalous or unusual woody structure with a swirled grain. The term lignotuber, which has a more restricted usage referring only to ontogenetically produced structures, should henceforth be used to describe these swollen “root crowns.” Investigations of lignotuber (burl) anatomy have revealed that the wood contains dormant buds, carbohydrates, and nutrients necessary for bud development. Reproductive strategies and tactics have evolved partially in response to the frequency and severity of disturbance (e.g., fire in shrublands of Mediterranean-type ecosystems). Reproductive strategies are defined by the timing and mode of production and reproduction. Reproductive tactics are the options of “reproductive effort” and energy allocation within each strategy. In the chaparral, fynbos, macchia, etc., one prevalent tactic in the sprouting strategy is the allocation of energy to the woody structure which has sprouting as its prime function—the lignotuber.

Family Elaeagnaceae is also known as oleaster family having three genera: Hippophae, Shepherdia and Elaeagnus, and about 70–80 species found worldwide. The multipurpose uses of genus Elaeagnus, their pharmacological significances and diverse chemical composition make them worthy of investigation and exploration for botanists and phytochemists. This critical review summarizes the botanical distribution, phytochemical constituents, and biological activities of various species of genus Elaeagnus. The online published material/papers available at different search engines were studied to compile this review. The existing literature available on search engines like Web of Science, PubMed, Science Direct, Springer, Elsevier, Scopus, Taylor and Francis, ACS publications, Google Scholar and Wiley On-line Library, was screened to collect relevant data. Elaeagnus species are widely used to treat a number of health issues due to their God gifted phytochemical compositions having great beneficial health applications. Phytochemical and biological evaluation studies have revealed the presence of essential chemical constituents like flavonoids, phenolic acids, carotenoids, terpenoids, lignanoids, organic acids, coumarins, alkaloids, steroids, vitamin C, lycopene, and polyphenols in Elaeagnus species that are responsible for their remarkable observed biological activities like antioxidant, antidiabetic, antibacterial, muscle relaxant effect, anti-diarrheal, antinociceptive, anticancer, anti-inflammatory, hepatoprotective, neuroprotective, and anti-amnesic activities. This review presents the importance of some species of genus Elaeagnus in terms of their traditional medicinal uses, phytochemical composition as well as potential pharmacological properties. However, bio-guided isolation studies are needed to understand the role of a particular compound in the observed biological activities.

Allelopathy and resource competition have often been suggested to explain plant-plant interference. Many studies have attempted to separate these two mechanisms of interference to demonstrate either as a probable cause of an observed growth pattern. We, however, are of the opinion that separating allelopathy from resource competition is essentially impossible in natural systems. Furthermore, any experimental design to separate allelopathy and resource competition will create conditions that will never occur in nature. In this article, the ecological interaction between allelopathy and resource competition in natural systems is discussed.

The guiding principles for raising beekeeping products in developing countries provide support for commercializing honey production in order to generate income for beekeepers through the exploration of melliferous flora. The main objective of this study was to conduct a preliminary investigation into the pollen morphology of selected melliferous species that are frequently visited by honeybees in the vicinity of apiaries in the district of Mardan, Khyber Pakhtunkhwa. In this study, an updated overview was provided by reviewing the literature regarding palynological investigation of melliferous flora. The morpho-palynological features, dominant plant families visited by honeybees, and life forms of melliferous species were also discussed. The Acetolysis method was used to prepare the microscopic slides of pollen, measure and describe the qualitative and quantitative features using LM and SEM. Results showed maximum pollen polar and equatorial diameter in M. azadirachta (37.9 μm) and (40.9 μm) respectively. The polar to equatorial diameter ratio (P/E) was observed to be the highest in M. domestica (1.14). Colpi length was calculated to be the highest in the P. granatum (13.8 μm). The highest percentage of pollen fertility was calculated in V. tricolor (92.5%), whereas the lowest was in O. rosea (64.28%). Studied characters under LM and SEM have appeared as a useful tool for the delimitation of melliferous flora, which may lead to the correct identification of the potential and valuable bee floral resources for beekeepers. The outcomes of this study aid in the assessment of melliferous flora and help in providing conservation measures for the sustainable development of beekeeping and the honeybee flora of the region.

The late-nineteenth/early-twentieth century debate over homologous versus antithetic alternation of generations is reviewed. Supporters of both theories, at first, used Coleochaete as a model for the origin of land-plant life cycles. The early debate focused on the morphological interpretation of the sporophyte and on whether vascular cryptogams had bryophyte-like ancestors. The terms of the debate shifted after the discovery that the alternation of morphological generations was accompanied by an alternation of chromosome number. Supporters of homologous alternation now promoted a model in which land plants had been derived from an algal ancestor with an isomorphic alternation of haploid and diploid generations whereas supporters of antithetic alternation favored a model in which land plants were derived from a haploid algal ancestor with zygotic meiosis. Modern evidence that embryophytes are derived from charophycean green algae is more compatible with an updated version of the antithetic theory.