scholarly journals Response of Bromus valdivianus (Pasture Brome) Growth and Physiology to Defoliation Frequency Based on Leaf Stage Development

Agronomy ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2058
Author(s):  
Iván P. Ordóñez ◽  
Ignacio F. López ◽  
Peter D. Kemp ◽  
Daniel J. Donaghy ◽  
Yongmei Zhang ◽  
...  
Keyword(s):  
Growth Rate ◽  
Stomatal Conductance ◽  
Root Growth ◽  
Water Soluble ◽  
Soluble Carbohydrates ◽  
Leaf Stage ◽  
Water Soluble Carbohydrates ◽  
Stage Development ◽  
Defoliation Frequency ◽  
Root Growth Rate

The increase in drought events due to climate change have enhanced the relevance of species with greater tolerance or avoidance traits to water restriction periods, such as Bromus valdivianus Phil. (B. valdivianus). In southern Chile, B. valdivianus and Lolium perenne L. (L. perenne) coexist; however, the pasture defoliation criterion is based on the physiological growth and development of L. perenne. It is hypothesised that B. valdivianus needs a lower defoliation frequency than L. perenne to enhance its regrowth and energy reserves. Defoliation frequencies tested were based on B. valdivianus leaf stage 2 (LS-2), leaf stage 3 (LS-3), leaf stage 4 (LS-4) and leaf stage 5 (LS-5). The leaf stage development of Lolium perenne was monitored and contrasted with that of B. valdivianus. The study was conducted in a glasshouse and used a randomised complete block design. For Bromus valdivianus, the lamina length, photosynthetic rate, stomatal conductance, tiller number per plant, leaf area, leaf weights, root growth rate, water-soluble carbohydrates (WSCs) and starch were evaluated. Bromus valdivianus maintained six live leaves with three leaves growing simultaneously. When an individual tiller started developing its seventh leaf, senescence began for the second leaf (the first relevant leaf for photosynthesis). Plant herbage mass, the root growth rate and tiller growth were maximised at LS-4 onwards. The highest leaf elongation rate, evaluated through the slope of the lamina elongation curve of a fully expanded leaf, was verified at LS-4. The water-soluble carbohydrates (WSCs) increased at LS-5; however, no statistical differences were found in LS-4. The LS-3 and LS-2 treatments showed a detrimental effect on WSCs and regrowth. The leaf photosynthetic rate and stomatal conductance diminished while the leaf age increased. In conclusion, B. valdivianus is a ‘six-leaf’ species with leaf senescence beginning at LS-4.25. Defoliation at LS-4 and LS-5 was optimum for plant regrowth, maximising the aboveground plant parameters and total WSC accumulation. The LS-4 for B. valdivianus was equivalent to LS-3.5 for L. perenne. No differences related to tiller population in B. valdivianus were found in the different defoliation frequencies.

scholarly journals The effect of grazing severity during winter on herbage regrowth and quality

2005 ◽  
pp. 141-146 ◽  
Author(s):  
J.M. Lee ◽  
D.J. Donaghy ◽  
J.R. Roche
Keyword(s):  
Water Soluble ◽  
Soluble Carbohydrates ◽  
Leaf Stage ◽  
Production Water ◽  
Appearance Rate ◽  
Water Soluble Carbohydrates ◽  
Leaf Appearance Rate ◽  
Residual Masses ◽  
Metabolisable Energy ◽  
Leaf Appearance

Grazing management is concerned with managing the interactions between plants and animals. Two management factors that require consideration are the optimal grazing time and the effect of grazing severity on subsequent regrowth. The objective of the current study was to quantify the effect of grazing severity in winter on leaf appearance r ate , herbage accumulation and quality, and plant energy r eserves. Ten pasture areas were grazed to two different residual masses (1260 ± 101 and 1868 ± 139 kg dry matter (DM)/ha, Severe and Lax, respectively) over five consecutive days by dry dairy cows. Neither growth rate (average 15 kg DM/ha/day), nor leaf appearance rate (average 16 days/new leaf) differed between treatments. As a result, herbage accumulated over the 49-day regrowth period was similar between grazing treatments (736 and 715 kg DM/ha for Severe and Lax, respectively), although herbage mass when three new leaves had emerged on regrowing tillers (third leaf stage) was greater on the laxly grazed treatment. Perennial ryegrass plants defoliated more severely displayed a trend for lower levels of water-soluble carbohydrates (WSC) than plants defoliated more laxly, but this difference had disappeared by the third leaf stage of regrowth. Pasture quality was improved in the severely defoliated treatment, with higher digestibility, WSC and metabolisable energy (ME) concentrations, and (ADF) lower acid and neutral detergent fibre (NDF) concentrations. Keywords: grazing sever ity, herbage production, water-soluble carbohydrates

Variation in the response of Lolium genotypes to defoliation

1994 ◽  
Vol 45 (6) ◽  
pp. 1309 ◽  
Author(s):  
WJ Fulkerson ◽  
K Slack ◽  
KF Lowe
Keyword(s):  
Root Growth ◽  
Lolium Multiflorum ◽  
Selection Criterion ◽  
Evaluation Process ◽  
Water Soluble ◽  
Soluble Carbohydrate ◽  
Plant Water ◽  
Leaf Stage ◽  
Defoliation Frequency ◽  
Water Soluble Carbohydrate

A glasshouse study was undertaken to determine the effect of defoliation frequency (three times at one leaf stage or once at three leaf stage of the regrowth cycle) and height (20, 50 or 120 mm) on regrowth, plant water soluble carbohydrate (WSC) reserves and root growth of seven Lolium perenne and two Lolium multiflorum cultivars. The sensitivity to defoliation was in decreasing order: biennial, PI perennials (cv. Ellett, AN2327, LP30, LP31), P2 perennials (cv. Kangaroo Valley, Yatsyn, Pacific). The effect of frequent, compared to infrequent, defoliation was to suppress regrowth by l00%, 95% and 80%; stubble WSC (mg/plant) by 97, 89 and 81%; root DM (g/plant) by 76, 60 and 6%, for biennial, P1 and P2, respectively. The effect of defoliation height accentuated this response, with biennials defoliated frequently at 20 mm stubble height all dying. Under defoliation conditions producing optimal yield, the yield was positively related to sensitivity to defoliation, giving regrowths of 2.90, 2.68, 1.53 g DM per plant for biennial, P1 and P2 plants, respectively. In view of the marked defoliation by cultivar interaction, response to defoliation should be considered as a possible selection criterion in any evaluation process.

Plant-soluble carbohydrate reserves and senescence - key criteria for developing an effective grazing management system for ryegrass-based pastures: a review

2001 ◽  
Vol 41 (2) ◽  
pp. 261 ◽  
Author(s):  
W. J. Fulkerson ◽  
D. J. Donaghy
Keyword(s):  
Dairy Cattle ◽  
Root Growth ◽  
Photosynthetic Capacity ◽  
Water Soluble ◽  
The Other ◽  
Soluble Carbohydrates ◽  
Soluble Carbohydrate ◽  
Carbohydrate Reserves ◽  
Water Soluble Carbohydrates ◽  
Water Soluble Carbohydrate

This review examines the use of changes in soluble carbohydrate reserves, and the onset of senescence in ryegrass (Lolium spp.), as key criteria for successfully managing an intermittent grazing system for dairy cattle. Ryegrass is a ‘3-leaf ’ plant; that is, only about 3 green leaves/tiller exist at any one time with the initiation of a new leaf coinciding with senescence of the oldest fourth leaf. Thus, grazing pasture older than 3 leaves/tiller will not only lead to wastage of pasture but also the senescent material will reduce overall quality of herbage. Based on this, the time taken for 3 new leaves/tiller to regrow sets the maximum grazing interval. On the other hand, in a well-utilised dairy pasture, most ryegrass leaf has been removed and the plant relies on stored water-soluble carbohydrate reserves to grow new shoots and hence regain photosynthetic capacity. If the concentration of water-soluble carbohydrates is inadequate, because there has been insufficient time to replenish in the previous inter-grazing period, regrowth will be suppressed and this may also affect persistence in the longer term. Immediately after grazing, water-soluble carbohydrate reserves decline as they are used to regrow new shoots, and root growth stops. It is not until about 3/4 of a new leaf/tiller has regrown that the plant has adequate photosynthetic capacity for growth and maintenance and only then does water-soluble carbohydrate replenishment and root growth commence. Studies have shown that subsequent regrowth is suppressed if plants are redefoliated before the 2 leaves/tiller stage of regrowth. Also, the levels of potassium and nitrogen (as nitrates and other non-protein nitrogen products) may be very high and cause metabolic problems in stock grazing such pasture. Thus, replenishment of water-soluble carbohydrate reserves sets the minimum grazing interval at 2 leaves/tiller. The rate of accumulation of water-soluble carbohydrates in the plant is a function of input through photosynthesis (source) and output to growth and respiration (sinks). Thus, apart from grazing interval (which sets the time to replenish water-soluble carbohydrate plant reserves), water-soluble carbohydrate storage will be influenced by incoming solar radiation (cloud cover, day length, pasture canopy density) and energy needs of the plant through respiration (temperature, canopy mass) and growth. Relating grazing interval to leaf number places the emphasis on the readiness of plants to be grazed rather than on the animals’ requirements, with leaf appearance interval depending primarily on ambient temperature. This allows grazing interval to be expressed in a similar morphological stage of growth, irrespective of season or location. Setting grazing interval on these 2 criteria has been shown to maximise growth and persistence of ryegrass and optimise the levels of most nutrients in pasture required by dairy cattle including protein, water-soluble carbohydrates, calcium, potassium and magnesium. Metabolisable energy and fibre do not change appreciably up to the 3 leaves/tiller stage of regrowth. On the other hand, grazing pasture before 2 leaves/tiller not only retards regrowth and reduces persistence, it provides forage too high in potassium and protein (nitrates) and too low in water-soluble carbohydrates for dairy cattle.

scholarly journals Root Morphology of Eight Hybrid Oil Palms Under Iron (Fe) Toxicity

2016 ◽  
Vol 1 (1) ◽  
pp. 013
Author(s):  
Aprilia Ike Nurmalasari ◽  
Eka Tarwaca Susila Putra ◽  
Prapto Yudono
Keyword(s):  
Growth Rate ◽  
Root Growth ◽  
Surface Area ◽  
Root Morphology ◽  
Block Design ◽  
Dry Weight ◽  
Root Volume ◽  
Oil Palms ◽  
Fe Toxicity ◽  
Root Growth Rate

The research aims to study the change of morphology root characters of eight hybrid oil palms under iron toxicity (Fe). Field experiment done in arranged in a Randomized Complete Block Design (RCBD) two factors and three blocks as replications. The first factor was Fe concentration. It consists of two levels which are concentration 0µ.g-1 and concentration 600 µg.g-1 Fe. The second factor is the hybrid of oil palms which consists of eight hybrid oil palms as Yangambi, Avros, Langkat, PPKS 239, Simalungun, PPKS 718, PPKS 540 and Dumpy. Fe was applied by pouring FeSO4 solvent for 600 µg.g-1 500 ml.-1plant.-1day-1 on two months of plants after transplanting in the main nursery. Data were collected on root morphology and plant dry weight The data were analysis of variance (ANOVA) at 5% significanly, followed by Duncan's multiple range test (DMRT). The relationships by among variables were determined by correlation analysis. The results showed that Fe concentration 600 µg.g-1 inhibits relatively root growth rate, narrows surface area, reduces the diameter, and shrinks root volume of all hybrid oil palms tested. The slowing relatively root growth rate, narrowing of root surface area and root diameter also root volume shrinkage due to Fe stress. It was also shown that the dry weight of plants was inhibit by existing of Fe toxicity.

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