. Asymbiotic seed germination and in vitro seedling development of Nothodoritis zhejiangensis . ( A ) Flowering specimen of N. zhejiangens growing on the tree branches of Cornus officinalis . ( B ) Seed germination and protocorm development in vitro. ( C
Song-jun Zeng, Zhi-lin Chen, Kun-lin Wu, Jian-xia Zhang, Cheng-ke Bai, Jaime A. Teixeira da Silva, and Jun Duan
Yoshiko Yambe, Kiyotoshi Takeno, and Takashi Saito
Seed germination percentage of multiflora rose (Rosa multiflora Thunh.) was much higher under continuous white light than in complete darkness. Red light was the most effective in inducing germination, and far-red light was ineffective. Exposure to red light for 1 min increased germination; this effect was saturated at an exposure of2 min. The red-light effect was reversed by subsequent exposure to far-red light. The results indicate that rose seeds are positively photoblastic, and that the photoreceptor involved is most likely phytochrome.
Robin A. DeMeo and Thomas E. Marler
Two studies were conducted to determine the influence of pH on papaya seed germination and seedling emergence. The germination test was conducted with `Waimanalo' and `Tainung 1' seeds, using a double layer of filter paper disks in plastic petri dishes placed within a growth chamber. Each dish received 40 seeds, and germination was defined as when the radicle was visible. Disks were wetted daily with nutrient solution adjusted to pH of 3, 4, 5, 6, 7, 8, or 9. Germination began on day 5, and the study was terminated on day 23. Solution pH did not influence germination rate or ultimate germination percentage. `Waimanalo' exhibited 58% germination and `Tainung 1' exhibited 64% germination in this test. The seedling emergence study was conducted with `Waimanalo' seeds using sand culture within a growth chamber. Thirty seeds were planted in 10-cm containers, and the sand was irrigated daily with the solutions from the first study. Emergence was defined as when the hypocotyl hook was visible above the sand. Emergence began on day 10, and the study was terminated on day 30. Solution pH did not influence seedling emergence, and mean emergence was 69% in this study. The results indicate that the seed germination and seedling emergence stages of papaya seedling growth are adapted to a wide range of substrate pH.
S. Grange, D.I. Leskovar, L. Pike, and G. Cobb
Triploid watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] consumption is increasing in the U.S. However, some of the original problems, poor and inconsistent germination, still exist. Seeds of several triploid and diploid watermelon cultivars were subjected to a variety of treatments to improve germination. Control and scarified seeds, by nicking, were incubated at 25 or 30 °C in either 5 or 10 mL H2O or hydrogen peroxide (H2O2). Triploid seed germination was strongly inhibited in all cultivars when seeds were at 10 mL of the H2O or H2O2; both nicking and H2O2 increased germination, but not equal to rate of the control in 5 mL H2O or H2O2. Germination of diploid cultivars was unaffected by any treatment. Seed morphological measurments indicated that triploid seed has a smaller embryo with a large and highly variable (CV = 105%) air space surrounding the embryonic axis as compared with the diploid seed. These data suggests that triploid watermelon seed germination is not inhibited by the seedcoat thickness alone. Seed moisture plays a significant role in germination, emergence, and stand uniformity.
S. Grange, D.I. Leskovar, L. Pike, and G. Cobb
Triploid watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] consumption is increasing in the United States However, some of the original problems, poor and inconsistent germination, still exist. Seeds of several triploid and diploid watermelon cultivars were subjected to a variety of treatments to improve germination. Control and scarified seeds, by nicking, were incubated at 25 or 30 °C in either 5 or 10 mL H2O or hydrogen peroxide (H2O2). Triploid seed germination was strongly inhibited in all cultivars when seeds were at 10 mL of H2O or H2O2; both nicking and H2O2 increased germination but not equal to rate of the control in 5 mL H2O or H2O2. Germination of diploid cultivars was unaffected by any treatment. Seed morphological measurments indicated that triploid seed has a smaller embryo with a large and highly variable (cv = 105%) air space surrounding the embryonic axis as compared with the diploid seed. These data suggests that triploid watermelon seed germination is not inhibited by the seed coat thickness alone. Seed moisture plays a significant role in germination, emergence, and stand uniformity.
James A. Schrader and William R. Graves
The genus Dirca L. (Thymelaeaceae) consists of three species of understory shrubs. Dirca palustris L. is sparsely distributed across eastern North America, D. occidentalis Gray is endemic near the San Francisco Bay, and D. mexicana Nesom & Mayfield is known only in one population in northeastern Mexico. Despite interest in the horticultural use of Dirca, plants seldom are marketed. Difficult propagation impedes production of Dirca. We sought to define protocols that promote uniform seed germination of all three Dirca spp. Endodormancy and paradormancy cause sporadic germination over several years under natural conditions, but endocarp removal, cold stratification, and treatment with GA3 increased germination percentage, speed, and uniformity. Dirca occidentalis was most responsive; up to 94% of seeds germinated after endocarp removal, 24 hours in GA3 at 50 mg·L–1, and stratification at 4 °C for 30 days. Treatments also were effective for D. palustris (up to 68% germination), but seeds of D. mexicana were unresponsive and germinated at 25% or less. Seed treatments should facilitate production of D. occidentalis and D. palustris, but further research is needed to define methods to propagate D. mexicana for horticultural use and for conserving this rare species in the wild.
Wayne A. Mackay and Tim D. Davis
Seeds of four lupine species (L. microcarpus var. aureus, L. havardii, L. succulentis, and L. texensis) were subjected to 0, –2, –4, –6, or –8 bars osmotic potential using PEG 8000 solutions. Seeds of all species were acid scarified prior to placement in petri dishes containing the osmotic solutions. Petri dishes were placed in a seed germination chamber at 25°C with germination data collected daily for 15 days. Seeds of L. havardii, a desert species native to west Texas exhibited the greatest germination as osmotic potential declined while L. succulentis, a species adapted to moist sites, exhibited the greatest decline in germination as osmotic potential decreased. The other species exhibited intermediate germinability under the lower osmotic potentials.
Joseph K. Peterson, Howard F. Harrison, and Maurice E. Snook
After removal of the periderm, cortex tissue of the sweetpotato cultivar Regal was collected. Polar extracts of this tissue strongly inhibited germination of proso-millet seed. C18 preparative, step-gradient chromatography (H2O → 100% methanol) gave some 50+ fractions, all of which were assayed for inhibitory properties. Analytical HPLC, using diode array detection and signal processing, showed the presence of chlorogenic, p-coumaric and caffeic acid, scopolin and some unknown phenolic acids. Most fractions were inhibitory to some degree; however, the least polar ones (in 90% and 100% methanol), containing unknown compounds, were most inhibitory. Semi-prep HPLC of these fractions produced eight major peaks (λmax at 210–213 nm, λ2 at 281–284 nm). In our bioassays, the compounds produced 50% inhibition of proso-millet seed germination at ≈60 ppm. It is likely that these compounds contribute significantly to the allelopathic properties of sweetpotato.
Carlma B. Bratcher, John M. Dole, and Janet C. Cole
The germination responses of wild blue indigo [Baptisia australis (L.) R. Br.], purple coneflower [Echinacea purpurea (L.) Moench.], Maximilian sunflower (Helianthus maximiliani Schrad.), spike goldenrod (Solidago petiolaris Ait.), and Missouri ironweed (Vernonia missurica Raf.) seeds after 0, 2, 4, 6, 8, or 10 weeks of stratification at 5C were investigated. Seed viability was determined using triphenyl tetrazolium chloride staining and germination based on the percentage of viable seeds. Germination percentage (GP) increased in all five species as weeks of stratification increased. Days to first germination and germination range (days from first to last germinating seed) decreased with increasing weeks of stratification, but the effect beyond 4 to 6 weeks was minimal. The number of weeks of stratification for maximum GP was 4 for purple coneflower, 6 for Maximilian sunflower, 8 for Missouri ironweed, and 10 for wild blue indigo and spike goldenrod.
Candice A. Shoemaker and William H. Carlson
Seeds of eight commonly grown bedding plant species [Ageratum houstonianum Mill., Begonia × semperflorens Hort., Impatiens wallerana Hook., Lobularia maritima (L.) Desv., Petunia × hybrida Hort., Pelargonium hortorum L.H. Bailey, Salvia splendens F. Sellow, Tagetes patula] were germinated at pH values from 4.5 to 7.5 at 0.5 increments. Seeds were germinated in petri dishes on filter paper saturated with buffer solutions or in petri dishes containing a 50 sphagnum peat: 50 coarse vermiculite (peatlite) medium moistened with buffer solutions. Germination on filter paper was affected by pH for all species tested. Peatlite medium pH affected germination of all species tested, except Salvia splendens. Species response to similar pH values differed between the two germination procedures. Total percent germination of seeds germinated was less in peatlite medium than on filter paper.