scholarly journals A Canopy Transpiration Model Based on Scaling Up Stomatal Conductance and Radiation Interception as Affected by Leaf Area Index

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 252
Author(s):  
Muhammad Shahinur Alam ◽  
David William Lamb ◽  
Nigel W. M. Warwick
Keyword(s):  
Stomatal Conductance ◽  
Leaf Area Index ◽  
Leaf Area ◽  
Festuca Arundinacea ◽  
Radiation Energy ◽  
Scaling Up ◽  
Controlled Environment ◽  
Canopy Conductance ◽  
Individual Layer ◽  
Area Index

Estimating transpiration as an individual component of canopy evapotranspiration using a theoretical approach is extremely useful as it eliminates the complexity involved in partitioning evapotranspiration. A model to predict transpiration based on radiation intercepted at various levels of canopy leaf area index (LAI) was developed in a controlled environment using a pasture species, tall fescue (Festuca arundinacea var. Demeter). The canopy was assumed to be a composite of two indistinct layers defined as sunlit and shaded; the proportion of which was calculated by utilizing a weighted model (W model). The radiation energy utilized by each layer was calculated from the PAR at the top of the canopy and the fraction of absorbed photosynthetically active radiation (fAPAR) corresponding to the LAI of the sunlit and shaded layers. A relationship between LAI and fAPAR was also established for this specific canopy to aid the calculation of energy interception. Canopy conductance was estimated from scaling up of stomatal conductance measured at the individual leaf level. Other environmental factors that drive transpiration were monitored accordingly for each individual layer. The Penman–Monteith and Jarvis evapotranspiration models were used as the basis to construct a modified transpiration model suitable for controlled environment conditions. Specially, constructed self-watering tubs were used to measure actual transpiration to validate the model output. The model provided good agreement of measured transpiration (actual transpiration = 0.96 × calculated transpiration, R2 = 0.98; p < 0.001) with the predicted values. This was particularly so at lower LAIs. Probable reasons for the discrepancy at higher LAI are explained. Both the predicted and experimental transpiration varied from 0.21 to 0.56 mm h−1 for the range of available LAIs. The physical proportion of the shaded layer exceeded that of the sunlit layer near LAI of 3.0, however, the contribution of the sunlit layer to the total transpiration remains higher throughout the entire growing season.

scholarly journals Effects of Potassium Management on Physiological Traiats, Enzyme Activity and Cotton Fiber Cellulose Content

2021 ◽  
Author(s):  
Fábio Echer ◽  
Vinicius José Souza Perez ◽  
Giuliano Oliveira Carnevalli Baltazar ◽  
Gustavo Ricardo Aguiar Silva ◽  
Adriana Lima Moro ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Stomatal Conductance ◽  
Leaf Area Index ◽  
Leaf Area ◽  
Cover Crops ◽  
Cotton Fiber ◽  
Cover Crop ◽  
Nutrient Use Efficiency ◽  
Cellulose Content ◽  
Area Index

Abstract AimsPotassium (K) is prone to be washed out of plant tissues independent of mineralization since it is not strongly bound to organic structures in the plant. Therefore, cover crops can enhance K cycling in cropping systems increasing the nutrient use efficiency by taking it up deep in the soil profile and releasing it on the soil surface. However, it is not clear if this cycling would have an effect on cotton morphophysiology, enzyme activity, and eventually on fiber quality. MethodsPotassium was applied to two cotton cultivars, either to the cover crop ruzigrass (Urochloa ruzisiensis), or to cotton grown after the grass or not, and split between the cover crop and cotton. ResultsCotton leaf area index was increased late in the season by K, with small differences between fertilized treatments, but was highest at full bloom when at least part of the K was applied to cotton. Stomatal conductance was improved, mainly late in the season and when cotton was grown after ruzigrass. Consequently, the enzymatic activity and accumulation of cellulose in the cotton fiber were also increased. ConclusionPotassium fertilization improves cotton physiological parameters such as leaf area index and stomatal conductance, but the effect on enzyme activity depends on the enzyme and on the cotton cultivar. Early cellulose accumulation in the fiber is favored by potassium fertilization and cotton rotation with ruzigrass.

Improving Seed Potato Leaf Area Index, Stomatal Conductance and Chlorophyll Accumulation Efficiency through Irrigation Water, Nitrogen and Phosphorus Nutrient Management

2016 ◽  
Vol 4 (1) ◽  
pp. 127 ◽  
Author(s):  
Gathungu Geofrey Kingori ◽  
Aguyoh Joseph Nyamori ◽  
Isutsa Dorcas Khasungu
Keyword(s):  
Stomatal Conductance ◽  
Leaf Area Index ◽  
Leaf Area ◽  
Chlorophyll Content ◽  
Seed Potato ◽  
Irrigation Water ◽  
Potato Leaf ◽  
Area Index ◽  
Water Rate ◽  
P Application

A study was conducted in a Rainshelter (RTrial) at Horticultural Research and Teaching Farm, Egerton University to determine the effect of integration of irrigation water, nitrogen (N) and phosphorus (P) application on seed potato leaf area index (LAI), stomatal conductance and chlorophyll content. The treatments arranged in a split-split plot layout in a completely randomised block design, consisted of three irrigation water rates (40%, 65% and 100% field capacity), four N rates (0, 75, 112.5 and 150 kg N/ha) supplied as urea (46% N), and four P rates (0, 50.6, 75.9, 101.2 kg P/ha) supplied as triple superphosphate, replicated three times and repeated once. During the growth leaf area, stomatal conductance, and chlorophyll content were measured. Data collected were subjected to analysis of variance and significantly different means separated using Tukey’s Studentized Range Test at P≤0.05. Leaf area index was greater with high irrigation water at 100%, N at 150 kg N/ha and P at 101.2 kg P/ha, which was 2.6 and 1.3 at 51 days after planting (DAP) and 3.5 and 3.1 at 64 DAP. Furthermore, low irrigation water rate at 40% together with low N and P rates of 0 kg N/ha and 0 kg P/ha had the least LAI, which was 0.28 and 0.19 at 51 DAP and 0.28 and 0.24 at 64 DAP both in RTrials I and II, respectively. Subjecting potato to 100% compared to 40% irrigation rate increased stomatal conductance at 87 days after planting (DAP) by 32.82 and 31.99 mmolm⁻²s⁻¹, leaf chlorophyll content index by 16.2 and 16.5, 19.8 and 19.6, and 15 and 20.3, when integrated with high compared with low N and P application rates at 59, 73 and 87 DAP, in RTrials I and II respectively. Irrespective of N and P rates LAI, stomatal conductance and chlorophyll content were significantly greater with high irrigation water at 100% followed by 65% and was lowest with 40% irrigation water rate.

Influence de l'indice foliaire et des réserves en hydrates de carbone au moment de la coupe sur la croissance foliaire de deux graminées fourragères (Dactylis glomerata L. et Festuca arundinacea Schreb.)

1996 ◽  
Vol 76 (2) ◽  
pp. 269-276 ◽  
Author(s):  
M. Duru ◽  
I. Calviere
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Festuca Arundinacea ◽  
Leaf Growth ◽  
Dactylis Glomerata ◽  
Variable Number ◽  
Area Index ◽  
Structural Carbohydrate ◽  
Dactylis Glomerata L ◽  
Tiller Density

Leaf growth of two forage grasses (Dactylis glomerata L. and Festuca arundinacea Schreb.) was studied as a function of the sward state after a cut. Two heights of cut (3 and 6 cm) and a variable number of previous cuts were used to reach different residual leaf area index (IFr), and non-structural carbohydrate (CNS) concentration and quantity. For both species, four treatments were studied in 2 consecutive years. In mid-May for each of the species, the IFr ranged from 0 to 1, and the quantity of CNS varied from 12 to 25 g 100 g−1 DM according to the treatments. Over the 3 wk of regrowth, the IF reached values ranging from 1 to 7 and its increase depended on the IFr and the quantity of CNS. Among the three components of the quantity of CNS (weight of sheath per tiller, tiller density and CNS concentration), only the first two had a significant effect on the IF increase. Tiller mortality occurred when the quantity of CNS or the IFr were the lowest and it contributed little to the growth of lower leaves. No significant differences were found between the two species. Key words: carbohydrates, leaf area index, tiller, cut

scholarly journals Grafting effect on photosynthetic activity and yield of tomato under a plastic house in Colombia

2021 ◽  
Vol 74 (3) ◽  
pp. 9621-9629
Author(s):  
Jamer Alexis Ramirez Jimenez ◽  
Paulo Eduardo Ribeiro Marchiori ◽  
Oscar de Jesús Córdoba-Gaona
Keyword(s):  
Stomatal Conductance ◽  
Quantum Yield ◽  
Leaf Area Index ◽  
Leaf Area ◽  
Dry Matter ◽  
Phenological Stages ◽  
Area Index ◽  
Tomato Yield ◽  
Use Efficiency ◽  
Radiation Use

Grafting is an effective approach to improve tomato yield and for tolerance to various abiotic and biotic stresses. This technique consists of using a vigorous or resistant plant (rootstock) to replace the root system of a genotype of economic interest (scion) but susceptible to one or more stress factors. The present work aimed to evaluate the physiological and productive response of a commercial tomato scion grafted on different rootstocks in Colombia’s high-Andean region. For this purpose, a tomato cv. Libertador was grafted on two commercial (“Olimpo” and “Armada”) tomato rootstocks in a randomized complete block experimental design. Four scion×rootstock combinations were evaluated by vigor rootstock, resistant rootstock, self-grafting, and non-grafted plants. Net photosynthesis, transpiration rate, stomatal conductance, water use efficiency, and radiation use efficiency were evaluated during six phenological stages (701, 704, 706, 708, 710, and 712), according to the BBCH scale; while the leaf area index and quantum yield were analyzed in five phenological stages (except 706). The highest values of photosynthesis, stomatal conductance, water and radiation use efficiency were registered in the initial phase of the production stage (701), which tended to decline at the end of the life cycle (712). Transpiration rate was similar throughout the growth cycle. Nevertheless, vigor rootstock presented the lowest photosynthesis rate; it was superior in terms of leaf area index, leaves dry matter, and tomato yield. The quantum yield values of the photosystem II did not indicate photochemical injuries in any of the scion×rootstock combinations. The higher tomato yield was reached in vigor rootstock and was associated with a more significant accumulation of dry matter in the leaf and higher leaf area index.

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