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Timothy L. Righetti, Carmo Vasconcelos, David R. Sandrock, Samuel Ortega-Farias, Yerko Moreno and Francisco J. Meza

; Righetti et al., 2007 ; Tanner, 1949 ) were evaluated to demonstrate how ratio-based assessments of CO 2 assimilation are strongly dependent on leaf size. Net photosynthetic rates (μmol·m −2 ·s −1 ) are usually expressed on a leaf-area basis. When we

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F.J. Montero, J.A. de Juan, A. Cuesta and A. Brasa

The importance of rapid, nondestructive, and accurate measurements of leaf area (LA) in agronomic and physiological studies is well known, but a search of the literature revealed little information available for grape (Vitis vinifera L.). The results described herein include a comparison of 12 different mathematical models for estimating leaf area in `Cencibel'. The simplest, most accurate regression equations were: LAi = 0.587 LW (R 2 = 0.987) and LAi = 0.588 LW (R 2 = 0.994), where LAi is leaf area measured using image analysis and LW is leaf length × maximum width. Use of maximum width (W), leaf length (L), petiole length (Lp), and dry weight of leaves (DML) as single variables in the regression equations were not as closely associated with total leaf area, although their R 2 values were also highly significant.

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Desmond R. Layne and J.A. Flore

Abbreviations: A, net CO, assimilation; A max , maximum net CO 2 assimilation; C i , internal CO 2 concentration; K, carboxylation efficiency LA, leaf area; LAR, leaf area removal; PPF, photosynthetic photon flux; R 1 , photorespiration; RuBP

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Carlo Fallovo, Valerio Cristofori, Emilio Mendoza de-Gyves, Carlos Mario Rivera, Roberto Rea, Simone Fanasca, Cristina Bignami, Youssef Sassine and Youssef Rouphael

Plant leaf area is an important determinant of light interception and consequently of transpiration, photosynthesis, and plant productivity ( Goudriaan and Van Laar, 1994 ). Plant physiologists and agronomists have demonstrated the importance of

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Aristidis S. Matsoukis, Ioannis Tsiros and Athanasios Kamoutsis

The effect of various plant growth regulators on leaf area development of Lantana camara L. subsp. camara was investigated under three photosynthetic photon flux (PPF) conditions (100%, 72%, and 34% light transmittance). The triazole compounds paclobutrazol (0, 50, 100, 200, and 500 mg·L-1) and triapenthenol (175, 350, 700, and 1400 mg·L-1), as well as the onium-type compounds mepiquat chloride (125, 250, 500, and 1000 mg·L-1) and chlormequat chloride (750, 1500, 3000, and 6000 mg·L-1), were applied as foliar spray solutions in each PPF level after pinching the plants. Leaf area, in general, decreased logarithmically as the concentrations of paclobutrazol and triapenthenol increased at all PPF levels. On the other hand, PPF reduction was found to increase leaf area of lantana plants treated with all concentrations of each regulator. Leaf area reduction of the paclobutrazol and triapenthenol treated plants at all PPF levels exceeded 60% compared with that of nontreated plants. However, the corresponding reduction was 22%, up to 51% for the plants treated with mepiquat chloride and chlormequat chloride. These results indicate that the triazole compounds have a greater effect on the reduction of lantana leaf area than the onium-type compounds. Chemical names used: (2RS, 3RS)-1-(4-chlorophenyl)-4, 4-dimethyl-2-(1H-1, 2, 4-triazol-1-yl) pentan-3-ol (paclobutrazol); (E)-(RS)-1-cyclohexyl-4,4-dimethyl-2-(1H-1, 2, 4-triazol-1-yl) pent-1-en-1-ol (triapenthenol); 1,1-dimethyl-piperidinium chloride (mepiquat chloride); (2-chloroethyl) trimethylammonium chloride (chlormequat chloride).

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Sergio Tombesi, Bruce D. Lampinen, Samuel Metcalf and Theodore M. DeJong

in almond trees), flower induction is related to the spur leaf area in the previous year and fruit bearing decreases the probability that a spur can bear flowers in the next year in comparison with spurs with similar leaf area that did not bear fruits

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Dennis R. Decoteau

, 1990 ; Tucker, 1977 ), and the factors involved in regulating axillary initiation and growth are not well understood. Leaf area distribution in a tomato canopy is important for maximizing plant photosynthetic capacity ( Wolk et al., 1983 ) and

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Angela Knerl, Brendon Anthony, Sara Serra and Stefano Musacchi

As the Pacific Northwest fruit industry shifts to precision-based management strategies for their orchards, tools are needed to understand tree physiology in the orchard to optimize fruit quality. Leaf area index is the ratio between the summed area

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Guofan Liu and Kent D. Kobayashi

It is difficult to estimate the total leaf area of coffee plants with accuracy due to the large number of leaves and the high leaf density of the plant canopy. In 1996, on Maui, Hawaii, 98 leaves of various sizes were randomly collected for each of five cultivars of Coffea arabica L. The cultivars used were `Guadalupe', `Guatemalan', `Mokka', `Red Catuai', and `Yellow Caturra'. Leaf length, width, and area were measured. Seventy-five leaves were used to develop leaf area models, and the remaining leaves were used to test the accuracy of the models using a 1:1 line. We then developed leaf area devices (LADs), which were made of sheet plastic and shaped to resemble coffee leaves. There were three groups of areas in the leaf area devices, based on leaf sizes. Total leaf area (TLA) contained three components. Each component related to the mean leaf area (k) and the number of leaves (n) in that group. The model for the total leaf area was: TLA = k1n1 + k2n2 + k3n3, where k is a constant in each group. The estimation errors for the different cultivars ranged from 5.6% to 12.3% for 1-year-old plants (four cultivars) and from 1.9% to 7.8% for mature plants (five cultivars). By using the LADs and counting the number of leaves, we can obtain the total leaf area for coffee plants in the field.

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Kent Kobayashi and Guofan Liu

One hundred mature leaves of macadamia (Macadamia integrifolia) were selected from 10 trees in a commercial orchard in Papaikou on the island of Hawaii. Length (L), width (W), and area (A) of each leaf were taken. L and W were significantly correlated (r = 0.93), L and A (r = 0.98), W and A (r = 0.94), and (L × W) and A (r = 0.99). L and W showed curvilinear relationships with A. Seventy-five mature leaves of coffee (Coffea arabica `Guatemalan') were selected from five trees at the Waimanalo Expt. Station on the island of Oahu. Leaf L, W, and A were measured. L and W were significantly correlated (r = 0.72), L and A (r = 0.89), W and A (r = 0.93), and (L × W) and A (r = 0.98). L and W showed curvilinear relationships with A. For both macadamia and coffee, although using L × W as a term in linear equations resulted in higher adjusted R 2s, the use of these equations would involve taking an additional measurement in the field. A quadratic equation using width (for coffee) or length (for macadamia) best described the relationship between these measurements and area and provide a quick method for estimating leaf area in the field.