Search

Autumn closing date (CD) in intensive pasture‐based systems influences spring herbage availability. Little is known about the impact of earlier closing of swards in autumn on sward structure. A two‐year experiment was undertaken to investigate the impact of five CD on herbage production, leaf extension rate (LER), leaf senescence rates (LSR), sward free leaf lamina (FLL) content and the production and survival of tillers over winter and into spring. The five CD ranges were October 1–15 (CD1), October 16–30 (CD2), October 31––November 14 (CD3), November 15–29 (CD4), November 30–December 14 (CD5) and sward measurements were made on four measurement dates (MD): December 11 (MD1), January 6 (MD2), January 27 (MD3) and prior to spring defoliation (MD4). Thirty perennial ryegrass tillers were measured until the first defoliation in spring (average 1 March). Herbage mass was greatest in early CD and tillers had greater LER and LSR (4.6 and 4.5 mm tiller−1 day−1 respectively) compared to swards with a later CD (3.2 and 2.3 mm tiller−1 day−1 respectively). Early CD had greater parent and daughter tiller mortality than later CD (parent tiller mortality 1.1 and 0.3 ± 0.19 tillers; daughter tiller mortality 1.1 and 0.3 ± 0.27 tillers respectively). Early CD also had greater LER and LSR in daughter tillers (2.6 and 1.5 mm tiller−1 day−1, respectively) compared to late (1.5 and 0.5 mm tiller−1 day−1, respectively). Earlier closing of sward increased herbage mass in spring, however, there were negative implications, such as increased LSR and tiller mortality. [ABSTRACT FROM AUTHOR]

The paper is focused on the assessment of leaf extension rate (LER), leaf appearance rate (LAR) and leaf senescence rate (LSR) in the Festulolium (Festuca arundinacea Schreb. × Lolium multiflorum Lam.) and in the Dactylis glomerata L. at the end of the growing season from the end of September to the beginning of December. In summer, the swards were used for a single cut (beginning of June) or for a double cut (beginning of June and end of July). Measurements were made in three periods from 14 Sept. to 11 Oct., from 11 Oct. to 29 Oct., and from 29 Oct. to 6 Dec. In the first period, LER was higher in Dactylis glomerata L. (3.770 mm tiller−1 d−1) than in Festulolium (2.376 mm tiller−1 d−1). In the second and third period, LER was higher in Festulolium (0.859 resp. 0.271 mm tiller−1 d−1) than in Dactylis glomerata L. (0.694, resp. 0.199 mm tiller−1 d−1). LAR values measured in Festulolium in the studied pe­riods were 0.277 leaf tiller−1 d−1, 0.079 leaf tiller−1 d−1 and 0.038 leaf tiller−1 d−1 and LAR values of Dactylis glomerata L. were 0.225 leaf tiller−1 d−1, 0.054 leaf tiller−1 d−1 and 0.027 leaf tiller−1 d−1. In the course of the whole pe­riod of study, LSR showed the highest values in Dactylis glomerata L. (7.869 mm til­ler−1 d−1, 5.947 mm til­ler−1 d−1 and 4.757 mm tiller−1 d−1) while the LSR values of Festulolium were lower (2.904 mm tiller−1 d−1, 2.375 mm tiller−1 d−1 and 1.205 mm tiller−1 d−1). The influence of both the species and the period of measurement on the LER, LAR and LSR values was statistically highly significant (P < 0.01) to very highly significant (P < 0.001). The interaction between the species and the period of measurement was very highly significant (P < 0.001) in the LER characteristic. The influence of the intensity of sward use in summer on the LSR values was very highly significant (P < 0.001), too.

Objetivou-se avaliar a dinâmica do aparecimento, do alongamento e da senescência de folhas do capim-elefante ‘Napier’ após pastejo de uniformização. O trabalho consistiu de dois experimentos, para o estudo de quatro tratamentos de adubação (T1: 100 kg de N e 80 kg de K, T2: 200 kg de N e 160 kg de K, T3: 300 kg de N e 240 kg de K e T4: 400 kg de N e 320 kg de K), sendo um irrigado e outro sem irrigação, segundo o delineamento de blocos ao acaso com três repetições. As plantas da área irrigada atingiram um maior número de folhas verdes (5 folhas) em um menor intervalo de crescimento (51,5 dias) do que as plantas não irrigadas (4,3 folhas em 68 dias). As taxas médias de aparecimento foliar foram 0,14 e 0,07 folhas/dia para os perfilhos basilares e aéreos, respectivamente. Observou-se resposta linear e positiva entre acúmulo de graus-dia (GD) e o índice de Haun, estimando-se filocronos de 84,0 e 150,8 GD para os perfilhos basilares e aéreos, respectivamente, na área irrigada. Para a área não irrigada os valores foram de 105,4 GD para os perfilhos basilares e 173,3 GD para os perfilhos aéreos. A taxa de alongamento foliar nos perfilhos basilares variou com a adubação; seu maior valor foi de 11,6 cm/dia referente à combinação de 200 kg/ha de N e 160 kg/ha de K. As plantas da área irrigada apresentaram maior taxa de alongamento foliar (11,58 cm/dia) em relação às da área não irrigada (7,99 cm/dia). A irrigação resultou em maior senescência foliar em ambos os tipos de perfilhos.The objective of this study was evaluate the leaf appearance, extension and senescence rates in ‘Napier’ elephant grass after uniformized graze. The study consisted of two experiments, for the evaluate the effect of four manuring treatments (T1: 100 kg of N and 80 kg of K, T2: 200 kg of N and 160 kg of K, T3: 300 kg of N and 240 kg of K and T4: 400 kg of N and 320 kg of K), on the an irrigated and no irrigated area , in a randomized block desing, with three replicates. The plants of the irrigated area reached a larger number of green leaves (5 leaves) in a smaller growth interval (51.5 days) that the plants not irrigated (4.3 leaves in 68 days). The average leaf appearance rates were 0.14 and 0.07 leaf/day for the basal and aerial tillers, respectively. Linear and positive answer was observed among degrees-day (DD) accumulation and the index of Haun, being considered phyllochron of 84.0 and 150.8 DD for the basal and aerial tillers, respectively, in the irrigated area. For the area not irrigated the values were of 105.4 DD to the basal tillers and 173.3 DD for the aerial tillers. The leaf extension rate in the basal tillers varied with the manuring; his largest value was of 11.6 cm/day regarding the combination of 200 kg/ha of N and 160 kg/ha of K. The plants of irrigated area shown a larger leaf extension rate (11.58 cm/day) in relation to that of the area not irrigated (7.99 cm/day). The irrigation resulted in larger leaf senencence in both types of tillers.

• Background and AimsNeotyphodium lolii is a fungal endophyte of perennial ryegrass (Lolium perenne), improving grass fitness through production of bioactive alkaloids. Neotyphodium species can also affect growth and physiology of their host grasses (family Poaceae, sub-family Pooideae), but little is known about the mechanisms. This study examined the effect of N. lolii on net photosynthesis (Pn) and growth rates in ryegrass genotypes differing in endophyte concentration in all leaf tissues.• Methods Plants from two ryegrass genotypes, Nui D and Nui UIV, infected with N. lolii (E+) differing approx. 2-fold in endophyte concentration or uninfected clones thereof (E−) were grown in a controlled environment. For each genotype × endophyte treatment, plant growth rates were assessed as tillering and leaf extension rates, and the light response of Pn, dark respiration and transpiration measured in leaves of young (30–45 d old) and old (>90 d old) plants with a single-chamber open infrared gas-exchange system.• Key ResultsNeotyphodium lolii affected CO2-limited rates of Pn, which were approx. 17 % lower in E+ than E− plants (P < 0·05) in the young plants. Apparent photon yield and dark respiration were unaffected by the endophyte (P > 0·05). Neotyphodium lolii also decreased transpiration (P < 0·05), but only in complete darkness. There were no endophyte effects on Pn in the old plants (P > 0·05). E+ plants grew faster immediately after replanting (P < 0·05), but had approx. 10 % lower growth rates during mid-log growth (P < 0·05) than E− plants, but there was no effect on final plant biomass (P > 0·05). The endophyte effects on Pn and growth tended to be more pronounced in Nui UIV, despite having a lower endophyte concentration than Nui D.• Conclusions Neotyphodium lolii affects CO2 fixation, but not light interception and photochemistry of Pn. The impact of N. lolii on plant growth and photosynthesis is independent of endophyte concentration in the plant, suggesting that the endophyte mycelium is not simply an energy drain to the plant. However, the endophyte effects on Pn and plant growth are strongly dependent on the plant growth phase. [ABSTRACT FROM AUTHOR]

Moisture and treading treatments were imposed on intact turves that were relocated to a glasshouse after being removed from three hill pastures of different soil fertility in the North Island of New Zealand. The experiment consisted of a 2-month stress phase, where the treatments were wetting (W), wetting and treading (WT), drying (D) and control (C). In this phase, herbage accumulation rate, tiller density and leaf extension rate were lower on the D turves, and herbage accumulation rate and tiller density were lower on the WT turves than for the C turves. Herbage accumulation rate was higher on the W treatment than on the C treatment. In the 2-month recovery phase, herbage accumulation rate and leaf extension rate on the D turves were higher than those of the C treatment. Herbage accumulation rate and tiller density took longer to recover on the WT turves but by the end of the recovery period tiller density on these turves exceeded that of the C turves and the original tiller densities on the WT turves. Changes (increase or decrease) in leaf extension rate were associated with the W treatment and tiller density with the WT treatment. Moisture was limiting on the D and C turves, but on the W and WT turves, where moisture was adequate for plant growth, nutrients were limiting, notably phosphorus on the W and WT turves and sulphur on the W turves. The D treatment turves recovered very quickly once the stress was removed but the WT turves were slower to recover. Under the experimental conditions applied, the hill pasture turves were more resilient to the drying treatment than the wetting and treading treatment. [ABSTRACT FROM AUTHOR]

Short-rotation coppice Salix genotypes of differing biomass yields were studied over two growing seasons with the long-term aim of identifying traits definitive of high yield for the breeding of elite energy crops. In the first season, basic leaf and stem traits were measured in six Salix genotypes, to identify morphological characteristics associated with high biomass yields. Thereafter, S. viminalis L. ‘L78183’ (low yield) and the hybrid genotype S. schwerinii E. Wolf× S. viminalis L. ‘Tora’ (high yield) were compared. Maximum stem heights and stem diameters increased with biomass yield. ‘Tora’ produced more sylleptic branches on the leading stems than ‘L78183’. Leaf traits differed significantly between the two genotypes: individual leaf area and cell number per leaf was greater in ‘Tora’, whereas cell area was greater in ‘L78183’, suggesting that final leaf areas were attained in ‘Tora’ through the production of many, small cells, and in ‘L78183’ through fewer, large cells. Leaf extension rates were higher in ‘Tora’ than ‘L78183’. This result was mirrored for leaf production rate. Leaf area index, examined at two coppice stages, was higher in ‘L78183’ (values of 2.06 and 1.67) than in ‘Tora’ (maximum value 1.43) which had a very open canopy. Furthermore, A/Ci analysis revealed the low-yielding genotype as the most photosynthetically efficient at the individual leaf level whereas light response curves suggest that ‘Tora’ utilised light more efficiently. The results presented in this study suggest that leaf extension rate, final leaf size and cell number per leaf may be indicative of yield, and may be useful as selection criteria for potentially high-yielding hybrids for biomass use. [Copyright &y& Elsevier]

Root tips of intact willow (Salix dasyclados Wimm., Clone 81-090) plants were partially dried by exposure to ambient greenhouse air and then kept in water-vapor-saturated air for up to 3 days. The drying treatment increased abscisic acid (ABA) concentrations in both the root tips subjected to drying and in the xylem sap, while it reduced leaf stomatal conductance and leaf extension rate. Despite the decrease in stomatal conductance, leaf water potentials were unaffected by the root drying treatment, indicating that the treatment reduced hydraulic conductivity between roots and foliage. After roots subjected to drying were returned to a nutrient solution or excised, ABA concentrations in the remaining roots and in the xylem sap, stomatal conductance of mature leaves and extension rate of unfolding leaves all returned to values observed in control plants. The 4-fold increase in xylem sap ABA concentration following the root drying treatment was not solely the result of reduced sap flow, and thus may be considered a potential cause, not merely a consequence, of the observed reduction in stomatal conductance. [ABSTRACT FROM PUBLISHER]

Genotypic variability in relation to growth and photosynthetic CO2 assimilation rate (Pn) is well known for maize (Zea mays L.) under heat stress conditions. This study was, however, initiated to test whether genotypic growth variation is related to variations in individual leaf size, leaf extension rate (LER), and photosynthesis of the single leaf at high temperature. Six tropical maize genotypes selected from the International Maize and Wheat Improvement Centre (CIMMYT) with contrasting growth responses were grown for 9 days after emergence (DAE) in the first and for 15 DAE in the second experiment at 25/22 °C and 42/30 °C. High temperature caused a marked decrease in the growth parameters, and the genotypes showed high growth variations irrespective of temperature levels. Interestingly, genotypes did not follow a similar ranking in relation to biomass production between 9 DAE (heterotrophic growth phase) and 15 DAE (autotrophic growth phase) at 25/22 °C, but the pattern was similar at 42/30 °C. Total leaf area and daytime LER of leaves 2 (l2), 3 (l3), and 4 (l4) showed a tight correlation with biomass production at both temperatures, while the LER of the youngest leaf (l4) at night also showed the same correlation at 42/30 °C. A significant relationship between the areas l2 and l3 and biomass was observed only at high temperature and not at 25/22 °C. The Pn decreased markedly at high temperature and genotypic variability was pronounced. The genotypes maintained a similar ranking of Pn measured from l2 at 8 DAE and from l3 at 13 DAE under unfavourable conditions only and not at 25 °C. Of the six genotypes, F250 outperformed the others in relation to growth and Pn activity. A tight correlation between photosynthesis of different leaves and growth was detected at high temperature but not... [ABSTRACT FROM AUTHOR]