Maximum Stem Length Research Articles

Variation in Development and Response to Root-zone pH Among Seedlings of Dirca palustris (Thymelaeaceae) from Three Provenances

Horticulturists have not promoted use of Dirca palustris L. (eastern leatherwood) despite its suite of traits valued by gardeners and landscapers. Horticultural production of D. palustris may be hindered by slow shoot growth and sensitivity of plants to edaphic conditions. Because of discrepancies in reported tolerances of D. palustris to root-zone pH, we assessed whether pH of soils supporting indigenous populations in Florida, Maine, and North Dakota corresponded to responses of seedlings from the three provenances to root-zone pH of 4.5 to 7.3 in soilless media. Regression showed that root zones at pH 5.8 promoted maximum stem length of seedlings from Florida and North Dakota, whereas root zones at pH 4.5 led to maximum stem length of seedlings from Maine. Root-zone pH 5.6 and 5.5 fostered maximum root and shoot dry weight, respectively, for seedlings from Florida, whereas root zones at pH 4.5 promoted maximum root and shoot dry weights of seedlings from Maine and North Dakota. Averaged over provenance, relative leaf greenness decreased by 62%, and foliar nitrogen, iron, manganese, and zinc decreased by 49%, 70%, 95%, and 48%, respectively, as root-zone pH increased from 4.5 to 7.3. Foliar phosphorus decreased at both low and high pH. The pH of soils where seeds were collected did not predict optimal root-zone pH for stem length or biomass accrual in soilless media; genotypes from soils with a pH of 7.4 in North Dakota did not exhibit greater tolerance to high pH than genotypes from Maine or Florida, where pH of indigenous soil was 6.1 and 5.2, respectively. Averaged over pH treatments, seedlings from Florida showed the greatest stem length and formed the most shoot biomass, whereas seedlings from North Dakota had stouter stems, greater root biomass, and greater root-to-shoot ratios than did seedlings from Florida and Maine. Our results illustrate that acidic media facilitate horticultural production of D. palustris, that further evaluation of provenance differences could facilitate selection of genotypes for horticulture, and that tolerances of genotypes to root-zone pH do not strictly correspond to the pH of soils on which they were indigenous.

IMPROVED MICROPROPAGATION OF WALNUT (JUGLANS REGIA L.) ON MEDIA OPTIMIZED FOR GROWTH BASED UPON MINERAL CONTENT OF WALNUT SEED

ISHS I International Symposium on Biotechnology of Fruit Species: BIOTECHFRUIT2008 IMPROVED MICROPROPAGATION OF WALNUT (JUGLANS REGIA L.) ON MEDIA OPTIMIZED FOR GROWTH BASED UPON MINERAL CONTENT OF WALNUT SEED

Studies on Yield and Yield Components of Spray Chrysanthemum (Chrysanthemum morifolium Ramat.) cv. Amal under Various Sources of Nitrogen

An investigation was undertaken to study the yield and yield components of spray-type chrysanthemum cv. Amal under variaous sources of nitrogen. The treatments considered different levels (100%, 75%, 50% or 25%) of four sources of nitrogen viz., urea, calcium ammonium nitrate, mustard cake and neem cake, alone or in combination of two or more of these. Results revealed that maximum stem length (62 cm) of cut flower and flower yield, number of flower heads (6387) and weight (4071.48 g/sqm) were mostly achiveved by application of total recommended dose of nitrogen through a combination of 25% N as neem cake + 25% N as mustard cake + 25% N as CAN + 25% as urea, and the treatment increased flower yield by 57.96% over treatment with nitrogen solely through urea. Flower size, individual flower weight, shelf and vase life of flower as well as anthocyanin content in floral tissue were higher in combined application of all oil cakes and urea and maximum under treatment combination of 50% recommended dose of nitrogen supplied through mustard cake, 25% N through neem cake and 25% N through urea. Anthocyanin content of flower tissues increased gradually upto 20 days from opening of the flower and, thereafter, declined sharply.

Seed size and response to rainfall patterns in annual grasslands: 16 years of permanent plot data

AbstractQuestion: Are seed size and plant size linked to species responses to inter‐annual variations in rainfall and rainfall distribution during the growing season in annual grasslands?Location: A 16‐year data set on species abundance in permanent plots 15 km north of Madrid in a Quercus ilex subsp. ballota dehesa.Methods: At species level, a GLM was used to analyse the effects of various rainfall indices (total autumn rainfall, early autumn rainfall and spring drought) on species abundance residuals with respect to time and topography. We also assessed the importance of seed size and plant size in the species responses at community level using species as data points. Seed mass and maximum stem length were used as surrogates for seed size and plant size, respectively.Results: Seed mass and plant size may explain some of the fluctuations in the floristic composition of annual species associated with autumn rainfall patterns. Species that are more abundant in dry autumns have greater seed mass than those species that are more abundant in wet autumns. Early autumn rainfall seems to favour larger plants.Conclusions: Our empirical results support the hypothesis that autumn rainfall patterns affect the relative establishment capacity of small and large seedlings in annual species.

Efeito de composto orgânico sobre a produção e características comerciais de alface americana

Doses de composto orgânico foram avaliadas na produtividade e qualidade da alface americana em um ensaio em Três Pontas, de 08/07 a 30/08/02. O delineamento utilizado foi em blocos casualizados com quatro repetições, sendo os tratamentos constituídos por cinco doses de composto orgânico (0,0; 20,0; 40,0; 60,0 e 80,0 t ha-1). A massa fresca total evidenciou um efeito quadrático, na qual a produtividade máxima de 914,2 g planta-1, foi obtida com a dose de 59,4 t ha-1 do composto orgânico. Para massa fresca comercial, a máxima produtividade (634,3 g planta-1), foi obtida com a dose de 56,1 t ha-1. A maior circunferência da cabeça comercial (41,4 cm), foi obtida com a dose de 53,7 t ha-1. A dose de 42,7 t ha-1 proporcionou um comprimento de caule máximo de 3,9 cm. Diante desses resultados, pode-se concluir que o uso de 56,0 t ha-1 de composto orgânico aplicado em pré-plantio, proporciona aumento de rendimento e qualidade comercial da alface americana.

Effects of the spatial arrangement of aerial stems and current‐year shoots on the demography and growth of Hydrangea hirta in a light‐limited environment

This study investigates the effects of the spatial arrangement of aerial stems and current-year shoots on patterns of herbivory, competition and on the requirements for mechanical support in Hydrangea hirta Sieb. et Zucc. growing in a light-limited environment. Stem demography was followed for three consecutive growing seasons. Stem mortality rates decreased with increasing stem age. Age-specific mortality rate was highest for new stems owing to the high incidence of herbivory. Mortality due to herbivory was low in older stems and was attributed to the dispersion of the risk of herbivore attack as a result of the increase in number of current-year shoots per stem. Clumping of stems led to intense intra-clonal competition as inferred from size-dependent mortality and density-dependent turnover of stems, and higher maximum stem length in clumps with higher stem density. Analysis of the spatial distribution of current-year shoots within the stem crown revealed a uniform, mono-layered crown architecture. The horizontal distribution of buds within the mono-layer was aggregated as a result of their opposite position, but as current-year shoots grew, their apices became uniformly distributed, resulting in efficient leaf display for light capture and shading out competing stems. However, limits on stem growth were observed in crown expansion, shoot production rate and current-year shoot size. Crown width increased with increasing basal diameter to reach a maximum. Both shoot production rate and current-year shoot size decreased with stem growth and a minimum current-year shoot size was defined. These limits on stem growth were attributed to suppression from intra-clonal competition and to the requirements for mechanical support of the mono-layered crown.