Search Results

You are looking at 11 - 20 of 957 items for :

  • User-accessible content x
Clear All
Free access

Xiaofeng Yang, Gang Li, Weihong Luo, Lili Chen, Shaopeng Li, Ming Cao, and Xuebin Zhang

nitrogen management, a model is needed for quantitatively assessing the impacts of nitrogen on growth dynamics and yield. The objective of this study was to develop a dynamics model to quantitatively investigate the impacts of nitrogen on growth dynamics

Free access

J.M.S. Scholberg, L.R. Parsons, and T.A. Wheaton

Improving our understanding of processes that control and limit nitrogen uptake by citrus can provide a scientific basis for enhancing nitrogen fertilizer use efficiency. Nitrogen uptake dynamics of two rootstock seedlings will be compared to those of young budded trees. Three-month old Swingle citrumelo [Citrus paradisi Macf. × Poncirus trifoliata (L.) Raf.] and Volkamer lemon (C. volkameriana Ten. & Pasq.) trees were planted in PVC columns filled with a Candler fine sand. Field experiments were conducted using 4-year-old `Hamlin' orange trees [Citrus sinensis (L.) Osb.] grafted on `Carrizo' [C. sinensis × Poncirus trifoliata (L.) Raf.] or on Swingle citrumelo. Trees were either grown in solution culture using 120-L PVC containers or in 900-L PVC tubs filled with a Candler fine sand. Additional trees were planted in the field during Spring 1998. Two lateral roots per tree were trained to grow in slanted, partly burried, 20-L PVC columns filled with a Candler fine sand. Nitrogen uptake from the soil was determined by comparing the residual N extracted by intensive leaching from planted units with that of non-planted (reference) units. With the application of dilute N solutions (7 mg N/L), plants reduced N concentrations to near-zero N concentrations within days. Applying N at higher concentrations (70 or 210 mg N/L) resulted in higher initial uptake rates, increased residual soil N levels, and reduced nitrogen uptake efficiency. Contributions of passive uptake to total nitrogen uptake ranged from less than 5% at soil solution concentrations around 3 ppm N to 20% to 30% at concentrations of 60 ppm N.

Full access

Xiaofeng Yang, Lianzhu Chen, Ming Cao, Xuebin Zhang, and Shaopeng Li

helpful to better understand the effect of fertilization on growth and quality of muskmelon. As an important foundation of modern agricultural expert management systems, the crop growth dynamics model has become a hot research topic in recent years. At

Open access

Rui Wang, Yuqing Gui, Tiejun Zhao, Masahisa Ishii, Masatake Eguchi, Hui Xu, Tianlai Li, and Yasunaga Iwasaki

and sink dynamics or supply and demand of photoassimilates. Plants produce photoassimilates in leaves as source organs and consume them to develop new leaves, stems, roots, and flower buds, which are referred to as sink organs. Photosynthesis is the

Free access

Dario Stefanelli*, Giovambattista Sorrenti, and Ronald L. Perry

Soil organic matter is a critical component which is fundamental in plant growth. Several soil factors are influenced by organic matter such as slow release of nutrients, increased water holding capacity, improved soil physical characteristics and improved environment for soil microorganisms. The aim of this work is to investigate the physical effect of organic matter content in the soil on apple root growth and development. Twenty five two-year old apple trees (Malus domestica, Borkh) cv. `Buckeye Gala' on M.9 NAKB 337 rootstock were planted in completely transparent acrylic boxes. Plants have been grown in a green house to avoid external rain in a complete randomized design. Trees were planted in a sandy-mix soil amended with soil high in organic matter, “muck”, at four incremental levels. Treatments compared were a control (sandy soil with 0% organic matter) and 1%, 2%, 4% and 8% soil organic matter. The amount of water applied by automatic drip irrigation was comparable for all the treatments to avoid high fluctuation of soil moisture on root dynamics. All treatments have been fertilized with the same amount of mineral fertilizer to avoid the nutrition effect on root dynamics. Digital photos of roots were taken to study their dynamics every one to two weeks during a period of five months. Roots have been highlighted with Photoshop and then analyzed with WinRhizo to measure root length, area, lifespan and dynamics. At the end of the growing period plants have been harvested and fresh and dry weight was evaluated to asses the root/shoot ratio. The effects of the treatments on root length, area, lifespan and dynamics, and root/shoot ratio will be discussed.

Free access

Boshou Liao and S.L. Kitto

In this study, the pod development dynamics and culture response in lima bean (Phaselous lunatus L.) were investigated. The average percentage of flowers to form pins was 17.5%. Pin length and width (mm), and weight (g) were all highly correlated with the days after pollination (DAP), with correlation coefficients of 0.98, 0.99 and 0.97, respectively. Pods grew relatively faster between 12 and 20 DAP, and reached their maximum length at about 35 DAP. Explants from pods of 5, 10, 15, 20, 25 DAP were cultured onto B5 medium containing BA (2 mg/L), kinetin (0.5 mg/L), 2,4-D (1 mg/L) or NAA (1 mg/L), sucrose (5%), and agar (0.7%). Soft calli only formed from the cut region on the seed coat or the suspensor attachment site of 5 and 10 DAP seeds. The 15 DAP explants were cultured as embryos (cotyledons 2 mm in length), and no callus was observed on them after 30 days of culture when they became brown. Twenty and 25 DAP embryos initiated calli and/or organ-like structures on the abaxial surface of cotyledons or embryo axes after 20 days of culture.

Free access

Shengrui Yao, Ian A. Merwin, and Michael G. Brown

Root observations in situ with a rhizotron camera enabled us to compare the performance of apple (Malus ×domestica Borkh.) trees on 3 rootstock clones planted in a New York orchard with a history of apple replant disease. Visual observations were conducted in situ at monthly intervals during 2 growing seasons through minirhizotron tubes for trees grafted onto 3 rootstocks: M.7 (M.7), Geneva 30 (G.30), and Cornell-Geneva 6210 (CG.6210). There were 3 preplant soil treatments (fumigation, compost amendment, and untreated checks) and 2 tree planting positions (within the old tree rows or in the old grass lanes of the previous orchard at this site). Preplant soil treatments and old-row versus grass-lane tree planting positions had no apparent influence on root systems, whereas rootstock clones substantially influenced root growth and demography. New root emergence was suppressed during the first fruit-bearing year (2004) on all 3 rootstock clones compared with the previous nonbearing year (2003). A root-growth peak in early July accounted for more than 50% of all new roots in 2003, but there was no midsummer root-growth peak in 2004. The median lifespan for roots of CG.6210 was twice that of G.30 and M.7 in 2004. Also, CG.6210 had more roots below 30 cm depth, whereas M.7 had more roots from 11 to 20 cm depth. Trees on CG.6210 were bigger, yielded more fruit, and had the highest yield efficiency in the third year after planting compared with trees on G.30 and M.7 rootstocks. Crop load appeared to inhibit new root development and changed root-growth dynamics during the first bearing year, with a resurgence in new root growth after fruit was harvested in October 2004. Rootstock genotype was the dominant influence on root lifespan and distribution in this study, whereas preplant soil fumigation, compost amendments, and replanting positions had little apparent impact on root characteristics despite their influence on above-ground tree growth and yield.

Free access

Jiaming Yu, Timothy K. Broschat, William G. Latham, and Monica L. Elliott

. Knowledge of phosphite distribution and dynamics in plant tissues is essential to determine the optimum timing for fungicide treatment and to predict which diseases it may be effective against. A study on the distribution and dynamics of phosphite in avocado

Free access

M. McLean, G.S. Howell, and A.J.M. Smucker

An experiment was conducted to evaluate interrelationships between differing crop loads and water stress on physiology and root dynamics of 3 year old Seyval grapevines grafted to 5-BB, Seyval and Seyval own-rooted stock grown under a rain exclusion shelter. Treatments were: 1) cropping level, either 0 (defruited) or 6 clusters/vine (heavily cropped) and 2) irrigation level, either 2.5 (stress) or 10 liters (control) of water/plant/week. Vines had significantly different root dynamics in regards to crop load, water status and rootstock. Water stressed vines had significantly fewer and smaller leaves (area cm 2 lighter trunk weights (g) and shorter shoot length compared to control vines. Heavily cropped vines had significantly fewer mature nodes, shorter shoot growth and higher bud mortality (winter injury) compared to defruited vines.

Free access

Dario Stefanelli, Roberto J. Zoppolo, and Ronald L. Perry

Fine root dynamics, timing of the events, and their relationship with soil conditions are of major interest because the understanding of these phenomena will permit a better synchronicity between nutrients and plant uptake. The goal of this research is to study the effect of different soil conditions, generated from two ground floor management systems, on fine root dynamics of apple trees under organic protocol in Michigan. The research has been conducted at the Clarksville Horticultural Experimental Station (CHES) of Michigan State University (MSU), in the organically certified (by OCIA) orchard of “Pacific Gala” grafted on M9 NAKB 337, established in May 2000. The orchard floor management systems being studied are: 1) a mulch made of alfalfa hay on the tree rows, with a width of 1.8 m and 2) the “Swiss Sandwich System” (SSS) that consists in superficial tillage of two strips 80 cm wide at each side of the tree row, leaving a 40 cm strip in the middle (on the tree row, under the canopy) where volunteer vegetation is allowed to grow. Root dynamics are studied on four replicas of two trees per each of the two ground treatments (16 in total) in a block design. For each tree in the trial four clear butyrate minirhizotrons have been installed (64 in total) at a 45° angle facing the tree, in the summer of 2002. Root dynamics, measured through pictures taken with a Bartz Technology digital camera and analyzed with a new software under development at MSU. During the 2003 season differences between the two systems have been found depending on the parameter taken in consideration. Mulch had different root distribution compared to SSS. Mulch treatment showed shallower roots even if below 90 cm the two systems didn't show any difference.