Mycorrhiza Co-Association with Aspilia pruliseta Schweif and Phosphorus Uptake Effects on Growth Attributes of Gadam Sorghum in Selected Sites in Kenya

ABSTRACTMycorrhiza fungi are important components of soil microbiota in the rhizosphere and greatly influence uptake of mineral elements to plants. A green house experiment was conducted at the University of Embu. The experiment involved use of sterilized polythene potting material sized 30 cm by 40 cm. The pots were filled two thirds the height of the potting material with soil from a predetermined source in Gakurungu, Tunyai and Kanyuombora in the upper eastern region in Kenya. The soil used in the pots was collected from the rhizosphere of Aspilia pruliseta Schweif vegetation as well as adjacent areas without this vegetation as a control at 0-20 cm, 21-40 cm and 41-60 cm for each of the soil types (silty clay, silt loam and sandy loam) used in the experiment. Two sorghum seeds inoculated with mycorrhiza fungi were planted in each pot and a similar number of pots planted with un inoculated sorghum seeds as a control. Each of the 4 treatments mentioned above, was replicated four times giving n=144. Each pot was watered after every two days using a two-litre watering can for the first one week. Thereafter, watering regime was reduced to once a week but ensuring the pots remained moist. Watering was done uniformly to all the pots. This was maintained for a period of thirty five days. Data was analysed using SAS edition 8.2. Seed emergence, hypocotyl development and stand count were enhanced at P≤0.05 in both mycorrhiza fungi inoculated gadam sorghum seeds and in pots whose soils were taken from the rhizosphere of Aspilia pruliseta plants. The growth attributes had a positive correlation to yield at 95% confidence. Soil phosphate level was enhanced in both cases of gadam seed inoculation with mycorrhiza and in soils previously grown Aspilia pruliseta vegetation.

Inhibitory Effects of the Lipophilic Extracts and An Isolated Meroditerpene of Brown Alga in Pasture Weeds in the Eastern Amazon Region

ABSTRACT: Two lipophilic extracts and atomaric acid (1), an isolated natural product, were obtained from the marine brown alga Stypopodium zonale (Dictyotaceae) to identify and characterize their potential inhibitory effects on the seed germination, radicle elongation, and hypocotyl development of the weeds Mimosa pudica and Senna obtusifolia. The extracts were prepared with hexane and dichloromethane, and atomaric acid (1) was isolated from hexane extract by way of conventional chromatographic methods. During a 15 days period, germination bioassays were performed at 25 oC with a 12 h photoperiod, whereas radicle elongation and hypocotyl development were assayed at 25 oC with a 24 h photoperiod. After, Petri dishes 9.0 cm in diameter were coated with qualitative filter paper, 25 seeds were placed in a germination chamber, while six pregerminated seeds were placed in the Petri dish for 2-3 days. After 10 days, radicle and hypocotyl extension were measured; and the inhibitory potential of the extracts was assessed at 10 ppm and that of the atomaric acid at 5, 10, 15, and 20 ppm. In both M. pudica and S. obtusifolia, dichloromethane extract achieved the greatest rates of inhibition during seed germination (34% and 22%, respectively), radical germination (38% and 30%, respectively), and hypocotyl development (29% and 22%, respectively). At a concentration of 20 ppm, atomaric acid (1) also demonstrated reduced inhibitory potential, with mean values of 58.67% for M. pudica and 48.67% for S. obtusifolia.

Comparative analysis of hypocotyl development in epiphytic, lignotuber-forming, and terrestrial Vaccinieae (Ericaceae)

A comparative analysis of hypocotyl development was undertaken with seedlings of three Vaccinieae (Ericaceae) species ( Macleania pentaptera Hoerold, Macleania rupestris (Kunth) A.C. Sm., and Vaccinium angustifolium Ait.) to determine the developmental basis for enlarged hypocotyls leading to the development of woody tubers (lignotubers) in M. pentaptera and M. rupestris. Differences in hypocotyl development are apparent after the first true leaves are visible in each species. Vascular tissue in M. rupestris and V. angustifolium is composed primarily of axial columns of secondary xylem. Secondary xylem tissues in M. pentaptera remain mostly parenchymatous and form radial columns of cells through numerous periclinal divisions. Furthermore, the secondary xylem of M. pentaptera comprises random networks of interconnected, small xylem elements in comparison with the secondary xylem of M. rupestris and V. angustifolium. These differences in hypocotyl development persist through the first 200 d of hypocotyl development, and ultimately lead to the development of a large lignotuber in M. pentaptera. Given the large amounts of parenchymatous tissue, a secondary xylem of relatively short secondary xylem elements, and the absence of adventitious buds, we propose that the lignotubers of M. pentaptera are used for short term water storage, rather than regeneration.

Responses ofIpomoeaspp. and Smallflower Morningglory (Jacquemontia tamnifolia) to Temperature and Osmotic Stresses

Seed germination responses to temperature and osmotic stress were determined for smallflower morningglory [Jacquemontia tamnifolia(L.)Griseb.] and seven species ofIpomoea.Cypressvine (I. quamoclitL.), willowleaf (I. wrightiiGray) and smallflower morningglory germinated and seedlings developed more slowly than the other morningglories at 16 C. Maximum germination of ivyleaf [I. hederacea(L.), Jacq. var.hederacea], entireleaf [I. hederacea(L.) Jacq. var.integriusculaGray], pitted (I. lacunosaL.), tall [I. purpurea(L.) Roth], cotton (I. trichocarpaEll.), and smallflower morningglories occurred in 24 h at 20 C. Cypressvine and willowleaf morningglories reached maximum germination in 24 h at 24 C. Optimal root-hypocotyl development occurred at 24 C for pitted, tall, and willowleaf morningglories, while all other species required a temperature of 28 C for maximal root-hypocotyl development in 4 days. Increasing osmotic pressure decreased or delayed germination of all morningglory species. Species tolerance to osmotic stress during germination could be ranked, most to least tolerant, as follows: ivyleaf=entireleaf>pitted=cotton>tall = willowleaf>cypressvine=smallflower. Maximum germination was delayed approximately 24 h for each 2 bar increment increase in osmotic pressure.

Gibberellic acid induced elongation of lettuce hypocotyls and its inhibition by colchicine

Lettuce (Lactuca sativa L.) seedlings treated with gibberellic acid (GA) for 72 h produced hypocotyls 600% longer than the water controls. The process of elongation was accelerated by GA. Also, for maximum elongation, presence of GA was not necessary after 20 h. Short term treatments of seedlings with GA indicated that the seedlings were most 'sensitive' to GA after 8 h of growth in water. Colchicine inhibited the GA-induced elongation. Its effect was maximal if it was applied within the first 2 h after GA treatment irrespective of the stage of hypocotyl development; the inhibition was progressively lessened after 2 h and lost after 36 h. These kinetic data are presented together with measurements of hypocotyl cell lengths and widths and provide a basis for correlated ultrastructural studies.