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Morphological and functional seed traits have important roles in characterising the species regeneration niche and help to understand the reproductive biology of rare and threatened plants, which can thus support appropriate plant conservation measures.Seed morphometric and dispersal kinetics of the critically endangered Dioscorea strydomiana were measured and compared with those of four other Dioscorea species, and seed germination response under constant temperatures (5–35 °C) was compared with that of the congeneric and widespread D. sylvatica.Seed mass of D. strydomiana (ca. 14 mg) was twice that of D. sylvatica, but similar to or smaller than the other species examined. Seeds of D. strydomiana have the lowest speed of descent and lowest variability in most of the morphological traits considered, suggesting lower phenotypic plasticity but higher variance in the wing‐loading value. Seeds of D. strydomiana reached maximum germination at 15 °C (ca. 47%), which decreased slightly to ca. 37% at 25 °C and was completely inhibited at 35 °C. D. sylvatica seeds started to germinate at 10 °C (ca. 3%), reached 75–80% germination at 15–20 °C and maximum (ca. 90%) at 25–30 °C. Base temperatures for germination (Tb) were 9.3 and 5.7 °C, for D. strydomiana and D. sylvatica, respectively. Due to the higher germination percentages of D. sylvatica, ceiling and optimum temperatures could also be modelled for this species, suggesting higher sensitivity to high temperature for seeds of D. strydomiana.The detected poor seed lot quality of D. strydomiana suggests difficulties in reproduction from seed, highlighting the need for further investigation and conservation actions for this threatened yam species. [ABSTRACT FROM AUTHOR]

Abstract: Anogeissus leiocarpa (DC.) Guill. & Perr. (Combretaceae) has important economic and cultural value in West Africa as source of wood, dye and medicine. Although this tree is in high demand by local communities, its planting remains limited due to its very low propagation via seed. In this study, X‐rays were used to select filled fruits in order to characterise their morphology and seed germination responses to treatment with sulphuric acid and different incubation temperatures. Morphological observations highlighted a straight orthotropous seed structure. The increase in mass detected for both intact and scarified fruits through imbibition tests, as well as morphological observations of fruits soaked in methylene blue solution, confirmed that they are water‐permeable, although acid‐scarified fruits reached significantly higher mass increment values than intact ones. Acid scarification (10 min soaking in 98% H2SO4) positively affected seed germination rate but not final germination proportions. When intact fruits where incubated at a range of temperatures, no seeds germinated at 10 °C, while maximum seed germination (ca. 80%) was reached at 20 °C. T50 values ranged from a minimum of ca. 12 days at 25 °C to a maximum of ca. 34 days at 15 and 35 °C. A theoretical base temperature for germination (Tb) of ca. 10 °C and a thermal requirement for 50% germination (S) of ca. 195 °Cd were also identified for intact fruits. The results of this study revealed the seed germination characteristics driven by fruit and seed morphology of this species, which will help in its wider propagation in plantations. [ABSTRACT FROM AUTHOR]

Threshold-based thermal time models provide insight into the physiological switch from the dormant to the non-dormant germinating seed., This approach was used to quantify the different growth responses of the embryo of seeds purported to have morphophysiological dormancy ( MPD) through the complex phases of dormancy release and germination. Aquilegia barbaricina seeds were incubated at constant temperatures (10-25 °C) and 25/10 °C, without pre-treatment, after warm+cold stratification (W+C) and GA3 treatment. Embryo growth was assessed and the time of testa and endosperm rupture scored. Base temperatures ( Tb) and thermal times for 50% (θ50) of embryo growth and seed germination were calculated., W+C enabled slow embryo growth. W+C and GA3 promoted rapid embryo growth and subsequent radicle emergence. The embryo internal growth base temperature ( Tbe) was ca. 5 °C for W+C and GA3-treated seeds. GA3 treatment also resulted in similar Tb estimates for radicle emergence. The thermal times for embryo growth (θe50) and germination (θg50) were four- to six-fold longer in the presence of GA3 compared to W+C., A. barbaricina is characterised by a multi-step seed germination. The slow embryo growth during W+C reflects continuation of the maternal programme of development, whilst the thermal kinetics of both embryo and radicle growth after the removal of physiological dormancy are distinctly different. The effects of W+C on the multiphasic germination response in MPD seeds are only partially mimicked by 250 mg·l−1 GA3. The thermal time approach could be a valid tool to model thermal kinetics of embryo growth and radicle protrusion. [ABSTRACT FROM AUTHOR]

Seed germination requirements of three underutilized Lippia (Verbenaceae) species were investigated. Seeds of L. graveolens, L. javanica and L. multiflora were incubated at a range of constant temperatures (5–35 °C) in the light (12 h light/12 h darkness). The effect of GA 3 and KNO 3 on seed germination was also tested in the same range of germination temperatures. Germination responses to accumulated temperature were then characterized by a thermal time approach. Two different trends of germination response to temperature were detected among species, regardless of the applied treatment. Seeds of L. graveolens and L. javanica started to germinate at 15 °C, reached their maximum germination at 25 °C and then decreased at warmer temperatures, while those of L. multiflora reached their maximum at the highest tested temperature (35 °C). Base temperature for germination (T b , °C) and the thermal constant for 50% germination (S, °Cd) of untreated seeds were ca. 2.5 and 7.5 °C and 76.92 and 84.3 °Cd, for L. graveolens and L. javanica , respectively. A T b of ca. 20 °C could only be roughly estimated for L. multiflora , due to the low germination achieved at temperatures < 35 °C. GA 3 and KNO 3 had an overall inefficacy on enhancing seed germination of these species. Thermal thresholds of treated seeds could also be estimated for L. javanica , with a T b of ca. 11 °C for both treatments and a S of 70.92 and 69.44 °Cd for GA 3 and KNO 3, respectively. Practical applications of the findings of this study may support the propagation of these underutilized Lippia species. [ABSTRACT FROM AUTHOR]

A germination study was carried out on seeds ofClinopodium sandalioticum(Bacch. & Brullo) Bacch. & BrulloexPeruzzi & Conti (Lamiaceae), a wild aromatic plant endemic to Sardinia. Seeds were incubated at a range of constant (5–25°C) and an alternating temperatures regime (25/10°C), with 12 hours of irradiance per day. The results achieved at 10°C were also compared with those obtained after a period of cold stratification at 5°C for three months. Final seed germination ranged from ca. 28% (5°C) to ca. 72% (25/10°C). A base temperature for germination (Tb) of ca. 5°C and a thermal constant for 50% germination (S) of 89.3°Cd were identified and an optimal temperature for germination (To) was estimated to be comprised between 20 and 25°C. Cold stratification negatively affected seed viability and germination at 10°C. Although a typical “Mediterranean germination syndrome”, could not be detected forC. sandalioticumseeds, these results were coherent with those previously reported for other Mediterranean Lamiaceae species. [ABSTRACT FROM AUTHOR]