Preliminary study on in vitro shoot culture of Hibiscus coddii subsp. barnardii, an indigenous South African flowering plant

In vivo and in vitro grown plants of Hibiscus coddii subsp. barnardii were used as explant source for establishment of in vitro cultures. Nodal shoot explants derived from in vivo grown plants, both naturally and under controlled environmental conditions, showed high sensitivity to the surface disinfection treatment and poor survival in in vitro culture. In vitro grown seedlings proved successful as aseptic source of apical and basal shoot explants to establish contamination-free in vitro cultures. Sprouting of axillary buds was observed on 90% of apical shoot explants after four weeks of culture on full strength, plant growth regulator (PGR)-free Murashige and Skoog (MS) medium. However, further proliferation of short shoots, limited to the bud sprout at the explant base, occurred on only 50% of these explants. In contrast, all basal shoot explants attained 3-5 single primary axillary shoots (30-40 mm in length) while a clump of short (5-10 mm) shoots also formed at the base in 60% of these explants. In both explant types, addition of 0.25-1 mg L-1 6-Benzylaminopurine (BAP) to the MS medium resulted in a low frequency (10%-60%) of explants with short shoots (5-10 mm) that showed no further elongation. Moreover, explants cultured in the presence of BAP showed a high frequency of callus formation (up to 90%) and low survival (20%-60%). A lower frequency of callus formation (30%-40%) and higher survival (90%-100%) of both explant types occurred on BAP-free medium. Further subculturing of primary and secondary axillary shoots onto fresh MS medium (with and without BAP) did not improve shoot multiplication. Regenerated plantlets from PGR-free MS medium were successfully acclimatized and hardened-off.

Blurring the Boundaries between a Branch and a Flower: Potential Developmental Venues in CACTACEAE

Flowers are defined as short shoots that carry reproductive organs. In Cactaceae, this term acquires another meaning, since the flower is interpreted as a branch with a perianth at the tip, with all reproductive organs embedded within the branch, thus giving way to a structure that has been called a “flower shoot”. These organs have long attracted the attention of botanists and cactologists; however, the understanding of the morphogenetic processes during the development of these structures is far from clear. In this review, we present and discuss some classic flower concepts used to define floral structures in Cactaceae in the context of current advances in flower developmental genetics and evolution. Finally, we propose several hypotheses to explain the origin of these floral shoot structures in cacti, and we suggest future research approaches and methods that could be used to fill the gaps in our knowledge regarding the ontogenetic origin of the “flower” in the cactus family.

Recovery of heather (Calluna vulgaris) flowering in northern Finland

Heather is a slow-growing evergreen shrub, commonly found in moorlands and heaths of high nature conservation value. Heather-dominated areas are used as livestock pasture, and the flowers of heather are harvested also for the natural product industry. Classical studies have focused on the recovery of shoot biomass of heather, while the recovery of flowering after grazing or harvesting has received less attention. In this study, we examined the recovery of heather flowering in one harvesting experiment and two observational areas in northern Finland. The flowers of heather were collected manually by clipping the flowering shoots or stripping the flowers from the shoots or by machine harvesting. We counted the number of short shoots (SS), nonflowering long shoots (NFLS), and flowering long shoots (FLS) after harvesting. We also measured the length of FLS and counted the flowers they produced. Heathers started to recover by producing new short shoots, while the recovery of flowering was slow, and only in one out of the three areas, flowering recovered totally during our study. Our results suggest that the recovery was dependent on the age of heather or individual site characteristics rather than on the harvesting method. Because flowering is one of the most important stages of successful reproduction, which affects the long-term existence of heather-dominated ecosystems, the results of our study can contribute to new guidelines for management practices in heathlands. However, longer-term experiments on the rate of flowering recovery are needed especially if rotational cutting is favored as a management practice in heathlands in the future.

Early Shoot Development Affects Carbohydrate Supply and Fruit Quality of Red-Fleshed Actinidia chinensis var. chinensis ‘Zes008’

Fruit quality characteristics are highly variable across kiwifruit vines due to complex source-sink interactions. We investigated how variation in fruit quality of Actinidia chinensis (Planch.) var. chinensis ‘Zes008’ was influenced by different shoot types (short, medium or long) and rootstocks types (Actinidia chinensis (Planch.) var. deliciosa (A. Chev.) ‘Bruno’ or Actinidia macrosperma C.F. Liang). Short shoots had smaller leaves (−30 to −50%) and lower photosynthesis rates (−0.70 to −3.34 µmol m−2 s−1) in the first cluster of nine leaves (Zone 1) compared with leaves on medium or long shoots. Later in the season, photosynthesis rates in Zone 1 declined with leaf age, but photosynthesis rates were higher (+0.5 to +6.1 µmol m−2 s−1) in later developing leaves on medium or long shoots. Fruit from short shoots had lower dry matter (−0.3 percent units) and lower outer pericarp flesh red pigment scores than fruit from medium or long shoots. At harvest, fruit from vines on ‘Bruno’ rootstocks were larger (+3.7 g), had higher dry matter (+1.3 percent units), soluble solids concentration (+1.7° Brix) and firmness (+0.4 kgf) than fruit from vines on A. macrosperma rootstocks. Factors that prioritised early development of source leaves had a direct impact on the carbohydrate supply from photosynthesis to support flower and fruit development.

Vascular bundle modifications in nodes and internodes of climbing Marantaceae

Nodes are interfaces between stems and leaves. Vascular bundles originate here and elongate into leaves and internodes. In Marantaceae, internodal bundles are highly diverse, including inverted bundles in the climbing genus Haumania. The objective of this paper is to characterize bundle forms, their position across the stem and their connection to leaves and short shoots in Haumania spp. and other unrelated African branch-angle climbers in the family (Hypselodelphys, Trachyphrynium). We question whether bundle inversion is a genus-specific trait in Haumania or related to the climbing growth form. Vascular bundles in internodes are scattered across the stem diameter in a characteristic pattern. Four (to five) bundle types follow each other in a centripetal order from highly sclerenchymatic ‘a’-bundles close to the epidermis to ‘d’-bundles in the centre with a low sclerenchyma proportion. Inverted bundles only appear in internodes of Haumania, making this trait a synapomorphy for the genus. The nodes show stem, leaf and short shoot bundles in a remarkably diverse pattern with partitioned phloem clusters and apparently augmented xylem elements. Our preliminary conclusion is that the inversion of bundles happens when leaf and short shoot traces join the main axis bundle layers.

Multiple stressors result in reduced reproductive effort by Thalassia testudinum in Florida Bay, USA

Sexual reproduction remains an understudied aspect of seagrass ecology. We examined spatiotemporal variability in the percentage of short shoots with sexual reproductive structures and the proportion of sites that had flowered as an indicator of Thalassia testudinum sexual reproductive effort (RE) across Florida Bay, USA. Short shoots were collected annually during spring within 13 basins across the bay from 2006-2019. The sample period followed 2 very active hurricane seasons and included 2 subsequent major disturbance events, a large-scale die-off of seagrasses in 2015, and the passage of Hurricane Irma in 2017. On average, 4.7% of the collected short shoots had flowered between 2006 and 2019, ranging from 1.3-8.5% at the bay scale and 0-30% at the basin level. Regression analyses indicated that RE varied significantly among basins and years, with high multiyear variability in several basins. RE was negatively correlated with annual heat accumulation, and positively correlated with the number of days below 28°C. Annual heat accumulation rose steadily from 2006-2019; accordingly, bay-wide RE declined. RE was higher in western basins, which were the most affected by recent disturbance events, indicating a potentially important role for sexual reproduction in recovery from disturbance. However, significant reductions in RE following the 2015 die-off and Hurricane Irma show limits to the plasticity and resilience of T. testudinum, both in terms of reduced compensatory RE following successive disturbances and reductions in basal RE correlated with rising annual temperatures.

A new species of Myrsine (Primulaceae-Myrsinoideae) from New Guinea

Myrsine exquisitorum Utteridge & Lepschi (Primulaceae-Myrsinoideae) is described and illustrated as a new species endemic to the Western Highlands Province from Papua New Guinea. The new species is unique in the relatively large, almost orbicular leaves with entire margins, and the tetramerous flowers arranged in axillary fascicles without forming short shoots.

From the frying pan: an unusual dwarf shrub from Namibia turns out to be a new brassicalean family

Tiganophyton karasense, an evergreen dwarf shrub, is described as a new species. A new genus and family are also proposed for it in the order Brassicales. Phylogenetic analysis of DNA sequence data indicate that Tiganophyton is sister to Bataceae/Salvadoraceae, and all three sister to Koeberliniaceae. First realized to be undescribed in 2010, T. karasense is a rare species known only from three localities in the arid Karas Region, southern Namibia. These small shrubs grow near the edges of seasonal pans on calcareous substrate underlaid by shales and mudstones of the Prince Albert Formation of the Karoo Supergroup. Morphological characters diagnostic of the new family include: a marked differentiation into long and short shoots; dimorphic, spirally arranged leaves; glucosinolate production; bisexual laterally flattened flowers borne singly in bract axils on short shoots only; tetramerous calyx, corolla and androecium with fused sepals and free, non-clawed petals; a staminal disc, but no nectary glands; deeply bilobed ovary with a gynobasic style; S-shaped gynophore supporting a bilocular, horizontally orientated or inverted ovary; two ovules per locule; and a dry, persistent fruit, provisionally interpreted as a one-seeded nutlet. Based on IUCN Red List categories and criteria, a conservation assessment of Vulnerable (VU D1) is recommended for Tiganophyton karasense.

Short Shoot Growth and Reproduction Response to Light Conditions Vary with Order Branching in the Proximal Part of C. atlantica Crown

This study compared the effects of shading in individual branch orders 2 and 3 on the needle survival, growth, and reproduction of five categories of short shoots of the proximal part of wild Atlas cedar (Cedrus atlantica (Endl.) G. Manetti ex Carrière). The sun exposure did not affect the number of short shoots in the two branch orders, whereas light compared to shade only stimulates the unbranched short shoot elongation of the branch order 3. The impact of shade exposure compared to sun on the loss of needles depends on the order of branching; it is weak to order 2 and increases to higher order. This effect in the branch order 3 is achieved by a significant decrease of the fallen leaf number in the unbranched short shoot SSnr and the short shoot SS/T worn by Twigs while in the branch order 2 only short shoot SS (nr + r) loses significantly few needles. In terms of short shoot extension and needle loss, the SS/T of the branch order 3 behaves in the same way as the SS (nr + r) of the branch order 2. The shadow compared to sunlit only decreases significantly the production of pollen strobili of the branch order 2. Close relationships between short shoot extension, leaf life span, and pollen strobili production of axillary products in the proximal part of C. atlantica crown were found.