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Bill Shipley - One of the best experts on this subject based on the ideXlab platform.
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net assimilation Rate specific leaf area and leaf mass ratio which is most closely correlated with Relative Growth Rate a meta analysis
Functional Ecology, 2006Co-Authors: Bill ShipleyAbstract:Summary 1Data were compiled consisting of 1240 observations (614 species) from 83 different experiments published in 37 different studies, in order to quantify the Relative importance of net assimilation Rate (NAR, g cm−2 day−1), specific leaf area (SLA, cm2 g−1) and leaf mass ratio (LMR, g g−1) in determining Relative Growth Rate (RGR, g g−1 day−1), and how these change with respect to daily quantum input (DQI, moles m−2 day−1) and Growth form (herbaceous or woody). 2Each of ln(NAR), ln(SLA) and ln(LMR) were sepaRately regressed on ln(RGR) using mixed model regressions in order to partition the between-experiment and within-experiment variation in slopes and intercepts. DQI and plant type were then added to these models to see if they could explain some of the between-experiment variation in the Relative importance of each Growth component. 3LMR was never strongly related to RGR. In general, NAR was the best general predictor of variation in RGR. However, for determining RGR the importance of NAR decreased, and the importance of SLA increased, with decreasing daily quantum input in experiments containing herbaceous species. This did not occur in experiments involving woody species.
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trade offs between net assimilation Rate and specific leaf area in determining Relative Growth Rate relationship with daily irradiance
Functional Ecology, 2002Co-Authors: Bill ShipleyAbstract:Summary 1 Three sepaRate experiments were conducted, involving 27 herbaceous species and 14 woody species aged 15–30 days, in order to determine the Relative importance of net assimilation Rate (NAR), specific leaf area (SLA) and leaf weight ratio (LWR) in explaining interspecific variations in Relative Growth Rate. 2 Daily quantum inputs were 31·12 mol m−2 day−1 in the first experiment and 33·17 mol m−2 day−1 in the second and third experiments. This is about twice the typical irradiance of most other experiments in this area, but only about 85% of the daily photon flux in nature. Plants were cultivated in hydroponic sand culture in a solution containing 5·8 mm nitrogen. 3 RGR was strongly and positively correlated with NAR in all three experiments. RGR was weakly and negatively correlated with SLA, while the correlation between RGR and LWR was weak and variable. 4 These results are compared to those already published in the literature: the commonly reported result that interspecific variation in RGR is determined primarily by SLA is partly due to the low irradiance used in most experiments, and the Relative importance of SLA and NAR changes depending on irradiance. 5 A hypothesis is proposed in which direct and indirect effects of SLA on each of NAR and RGR are decomposed, and which leads to a trade-off between SLA and NAR as a function of daily irradiance.
M. Obopile - One of the best experts on this subject based on the ideXlab platform.
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Demographic parameters of cowpea aphid Aphis craccivora (Homoptera: Aphididae) on different Botswana cowpea landraces
International Journal of Tropical Insect Science, 2012Co-Authors: M. Machacha, M. Obopile, A. B. N. Tshegofatso, B. Tiroesele, C. Gwafila, M. RamokapaneAbstract:The variation in demographic parameters (namely survival and fecundity, intrinsic Rate of natural increase pre-reproductive period and Relative Growth Rate) was used to assess the resistance of cowpea landraces (namely B261-B, B383, B013-F, B339 and Blackeye, as a check) against cowpea aphid ( Aphis craccivora Koch). The experiment was carried out from 18 March 2011 to 5 April 2011. The demographic parameters of A. craccivora differed significantly among varieties, supporting our prediction that cowpea landraces resistant to cowpea aphid would have a significant effect on the demographic parameters of the aphid. We recorded significantly lower survival, fecundity, intrinsic natural Rate of increase and Relative Growth Rate on the landraces B261-B and B383 compared with the other landraces. A significant delay in the pre-reproductive period was also found on B261-B and B383. The results showed that landraces B261-B and B383 have an increased level of resistance as shown by the extended pre-reproductive period and the reduction in population Growth Rate, survival and fecundity. This information will be used in the characterization of the landraces before being incorpoRated in the breeding programme in Botswana.
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life table and population parameters of cowpea aphid aphis craccivora koch homoptera aphididae on five cowpea vigna unguiculata l walp varieties
Journal of Pest Science, 2010Co-Authors: M. Obopile, Baitheri OsitileAbstract:The cowpea aphid, Aphis craccivora Koch, is an important pest of cowpea Vigna unguiculata (L. Walp.) in most tropical regions where cowpea is grown. We used life table and population parameters of the cowpea aphids reared on five cowpea varieties to assess the degree of host plant resistance. The five varieties were Blackeye, B005-C, INIA-37, IT835-720-20 and TVX3671-14C-OID. The parameters measured were fecundity, survival, intrinsic Rate of natural increase, pre-reproductive period and Relative Growth Rate of cowpea aphids. Our hypothesis was that cowpea varieties resistant to A. craccivora would have significant effects on life table parameters of the aphid when compared to a susceptible variety. Mean fecundity, age-specific fecundity, survival Rates, intrinsic Rate of natural increase (r m), pre-reproductive period and Relative Growth Rate differed significantly among varieties. Fecundity, survival, intrinsic Rate of natural increase and mean Relative Growth Rate were significantly lower on variety IT835-720-20 compared to susceptible variety Blackeye. The pre-reproductive period was significantly delayed on variety IT835-720-20 compared to other varieties. The adverse effects of variety IT835-720-20 on life table parameters of A. craccivora indicate the presence of host plant resistance. Prolonged pre-reproductive period and reduction in reproductive performance of A. craccivora on variety IT835-720-20 may suggest that antibiosis is the modality of resistance. However, further detailed studies that include determination of biochemical and morphological characteristics that mediate resistance need to be carried out. IT835-720-20 is, therefore, a promising variety with useful genetic resource for cowpea breeding programs aimed at developing resistant varieties against A. craccivora.
Hans Lambers - One of the best experts on this subject based on the ideXlab platform.
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variation in Relative Growth Rate of 20 aegilops species poaceae in the field the importance of net assimilation Rate or specific leaf area depends on the time scale
Plant and Soil, 2005Co-Authors: Rafael Villar, Pilar Panadero, Francisco Arenas, Teodoro Maranon, José Luis Quero, Hans LambersAbstract:Field experiments reporting the Relative Growth Rate (RGR) patterns in plants are scarce. In this study, 22 herbaceous species (20 Aegilops species, Amblyopyrum muticum and Triticum aestivum) were grown under field conditions to assess their RGR, and to find out if the differences in RGR amongst species were explained by morphological or physiological traits. Plants were cultivated during two months, and five harvests (every 13–19 days) were carried out. Factors explaining between-species differences in RGR varied, depending on whether short (13–19 days) or longer periods (62 days) were considered. RGR for short periods (4 Growth periods of 13–19 days each) showed a positive correlation with net assimilation Rate (NAR), but there was no significant correlation with leaf area ratio (LAR) (with the exception of the first Growth period). In contrast, when Growth was investigated over two months, RGR was positively correlated with morphological traits (LAR, and specific leaf area, SLA), but not with physiological traits (NAR). A possible explanation for these contrasting results is that during short Growth periods, NAR exhibited strong variations possibly caused by the variable field conditions, and, consequently NAR mainly determined RGR. In contrast, during a longer Growth period (62 days) the importance of NAR was not apparent (there was no significant correlation between RGR and NAR), while allocation traits, such as LAR and SLA, became most relevant.
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Growth Rate plant development and water relations of the aba deficient tomato mutant sitiens
Physiologia Plantarum, 1994Co-Authors: Oscar W Nagel, Henk Konings, Hans LambersAbstract:Given the close relationship between a plant's growih Rate and its pattern of biomass allocation and the effects of ahseisic acid (ABA) on biomass allocation, we studied ihe influence of ABA on biomass allocation and Growth Rate of wildtype tomato (Lycopersicon esculenium Mill. cv. Moneymaker) plants and Iheir strongly ABA-deficienl mutant sitiens. The Relative Growth Rate of siiiens was 22'7f lower than that of the wildtype, as the result of a decreased specific leaf area. The net assimilation Rate and the leaf weight ratio were not affeeted. The mutant showed a mueh higher transpiration Rate and iower hydraulic conductance of the roots. These two factors resulted in sitiens having a significantly lower leaf water potential and turgor. resulting in reduced leaf expansion and, consequently, a lower specific leaf area Relative to the wildtype. Addition of ABA to the sitiens roots resulted in phenotypic reversion to Ihe wildtype. We conclude that the influenee of ,'\BA-deftciency on biomass allocation and Relative Growth Rate is the resuit of altered water relations in the plants, rather than of a direct effect on sink strength of different plant organs.
Rafael Villar - One of the best experts on this subject based on the ideXlab platform.
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variation in Relative Growth Rate of 20 aegilops species poaceae in the field the importance of net assimilation Rate or specific leaf area depends on the time scale
Plant and Soil, 2005Co-Authors: Rafael Villar, Pilar Panadero, Francisco Arenas, Teodoro Maranon, José Luis Quero, Hans LambersAbstract:Field experiments reporting the Relative Growth Rate (RGR) patterns in plants are scarce. In this study, 22 herbaceous species (20 Aegilops species, Amblyopyrum muticum and Triticum aestivum) were grown under field conditions to assess their RGR, and to find out if the differences in RGR amongst species were explained by morphological or physiological traits. Plants were cultivated during two months, and five harvests (every 13–19 days) were carried out. Factors explaining between-species differences in RGR varied, depending on whether short (13–19 days) or longer periods (62 days) were considered. RGR for short periods (4 Growth periods of 13–19 days each) showed a positive correlation with net assimilation Rate (NAR), but there was no significant correlation with leaf area ratio (LAR) (with the exception of the first Growth period). In contrast, when Growth was investigated over two months, RGR was positively correlated with morphological traits (LAR, and specific leaf area, SLA), but not with physiological traits (NAR). A possible explanation for these contrasting results is that during short Growth periods, NAR exhibited strong variations possibly caused by the variable field conditions, and, consequently NAR mainly determined RGR. In contrast, during a longer Growth period (62 days) the importance of NAR was not apparent (there was no significant correlation between RGR and NAR), while allocation traits, such as LAR and SLA, became most relevant.
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Relative Growth Rate in phylogenetically related deciduous and evergreen woody species
Oecologia, 2001Co-Authors: Isabel Antunez, Emilio C Retamosa, Rafael VillarAbstract:Relative Growth Rate (RGR) and other Growth parameters were studied in eight pairs of closely related deciduous and evergreen species (within the same genus or family). The main objective of this study was to test the association between leaf turnover Rate and RGR, specific leaf area (SLA, leaf area/leaf dry weight) and other Growth variables. Plants were grown for 6 months in a greenhouse under favourable water and nutrient conditions. Variation in RGR among the 16 woody species was due mainly to differences in morphological parameters such as leaf area ratio (LAR, whole plant area/whole plant dry weight) and SLA). However, temporal variation in RGR within species was due mainly to variation in net assimilation Rate. When phylogeny was not taken into account, analyses showed that deciduous species grew faster than evergreens. In contrast, when phylogeny was taken into account, the data analysis showed that a faster RGR is not consistently associated with the deciduous habit (in five pairs it was, but in the other three it was not). The faster Growth of the deciduous trees (in the five positive contrasts) could be explained by their higher LAR and higher SLA Relative to evergreens. The lack of differences in RGR between deciduous and evergreens (in three pairs) was due to the higher leaf mass ratio (LMR, leaf dry biomass/total dry biomass) for the evergreens, which offset the higher SLA of the deciduous species, resulting in a similar LAR in both functional groups (LAR=LMR×SLA). Deciduous species had consistently higher SLA than evergreens. We suggest that SLA, more than RGR, could be an important parameter in determining adaptive advantages of deciduous and evergreen species.
Baitheri Ositile - One of the best experts on this subject based on the ideXlab platform.
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life table and population parameters of cowpea aphid aphis craccivora koch homoptera aphididae on five cowpea vigna unguiculata l walp varieties
Journal of Pest Science, 2010Co-Authors: M. Obopile, Baitheri OsitileAbstract:The cowpea aphid, Aphis craccivora Koch, is an important pest of cowpea Vigna unguiculata (L. Walp.) in most tropical regions where cowpea is grown. We used life table and population parameters of the cowpea aphids reared on five cowpea varieties to assess the degree of host plant resistance. The five varieties were Blackeye, B005-C, INIA-37, IT835-720-20 and TVX3671-14C-OID. The parameters measured were fecundity, survival, intrinsic Rate of natural increase, pre-reproductive period and Relative Growth Rate of cowpea aphids. Our hypothesis was that cowpea varieties resistant to A. craccivora would have significant effects on life table parameters of the aphid when compared to a susceptible variety. Mean fecundity, age-specific fecundity, survival Rates, intrinsic Rate of natural increase (r m), pre-reproductive period and Relative Growth Rate differed significantly among varieties. Fecundity, survival, intrinsic Rate of natural increase and mean Relative Growth Rate were significantly lower on variety IT835-720-20 compared to susceptible variety Blackeye. The pre-reproductive period was significantly delayed on variety IT835-720-20 compared to other varieties. The adverse effects of variety IT835-720-20 on life table parameters of A. craccivora indicate the presence of host plant resistance. Prolonged pre-reproductive period and reduction in reproductive performance of A. craccivora on variety IT835-720-20 may suggest that antibiosis is the modality of resistance. However, further detailed studies that include determination of biochemical and morphological characteristics that mediate resistance need to be carried out. IT835-720-20 is, therefore, a promising variety with useful genetic resource for cowpea breeding programs aimed at developing resistant varieties against A. craccivora.
