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Comparison of Different Methods for Determining Leaf Area Index of Ornamental Pineapple
Leaves are the main organs of plants for photosynthesis, transpiration, and synthesis of organic matter, and they are the basis and source of energy for living on earth. The leaf area index, which refers to the total leaf area of ​​plants on a unit land area, is an important quantitative indicator of population structure. In the photosynthetic production process, leaf area index not only determines the area of ​​photosynthesis organs in crops, but also affects the distribution of light in the crop canopy, and thus is an important parameter to determine the total photosynthetic capacity of crop canopy. Some studies have confirmed that the appropriate leaf area index is conducive to the increase in yield. For ornamental plants, the size of the leaf area not only affects its growth, but also affects its appearance quality. Ornamental pineapples are a kind of high-grade potted flowers. Many evaluation indicators stipulated in the quality standards of potted flowers, such as crown width, crown height ratio, plant type, and leaf arrangement, have a great relationship with the size of the leaves. Therefore, the simple, rapid and accurate detection of the leaf area has important reference value for guiding the plant to be closely planted, adjust the population structure, and control the precise fertilizer and water management to achieve the goal of high quality or high yield.
There are many methods for measuring and calculating the leaf area. Currently, there are many methods that can be applied more accurately, such as leaf area meter, canopy analyzer, photoelectric planometry, leaf area scanner, etc. . However, these instruments are expensive and are still difficult to promote in production. In horticultural crops, predecessors have studied the simple method of leaf area determination. The results showed that leaf length, leaf width, leaf length and breadth were all significantly positively correlated with leaf area, and these traits were The leaf area was determined by single-leaf area linear regression analysis of the variables and the results were accurate and reliable. There was no significant difference from the measurement results of the leaf area meter. In this experiment, the leaf area of ​​ornamental pineapples was determined by leaf area meter method, canopy analyzer method and regression equation method. The advantages and disadvantages of the three methods and the scope of application were analyzed and evaluated. To provide reference for further studies on the biological characteristics and growth and development regularity of ornamental plants through the determination of leaf area, and evaluation of quality grades.
1 Materials and Methods
1. 1 test materials
The experiment was conducted in the Wenlo greenhouse in Holland in January 2007 at the Experimental Plant of Nanjing Vegetable and Flower Research Institute. The greenhouse grows from north to south and is 84 m long. It has 29 spans along the east-west direction. Each span spans 4 m, shoulder height is 4.3 m, and ridge height is 5 m. In the greenhouse, potted pineapples were produced. The tested varieties were “New World†and “Torchâ€. The planting density of “New World†was 8.66 plants/m2, and the planting density of “Torch†was 10.58 plants/m2.
1. 2 test methods
1. 2. 1 LA I-2000 Canopy Analyzer Assay The “New World†and “Torch†each select 5 points for each species. Each point measures 1 canopy value A and 4 canopy values ​​B, and repeats. 2 times. According to the method of row crops, the first B value is taken on the crop line, the second B value is taken off line 1/4, the third B value is taken in the middle of 2 lines, and the fourth B value is taken 3/4 off the line.
1. 2. 2 LI - 3000 Leaf Area Meter Assay "New World" and "Torch" Each species has a representative selection of 3 plants. The leaves are cut from the base and the leaf area is used to measure the area of ​​each leaf. Single leaf area was obtained.
1. 2. 3 regression equation determination (1) Each species of "New World" and "Torch" is randomly selected 30 kinds of leaves of various sizes and ages, cut it, measure the length of leaves, and then each leaf of the leaves Shaped on a copy paper prepared in advance, and finally cut the leaf paper weighing, to obtain its leaf area; (2) "New World" and "Torch" are selected for each species representative of the three strains, measuring each The leaves were long, and then the total leaf area of ​​each plant was calculated based on the regression equation.
1. 3 Principles of Different Measurement Methods
1. 3.1 Principles of the LA I-2000 Canopy Analyzer Assay The basic principle of the LA I-2000 canopy analyzer is that the number of vegetation canopy blades can be deduced by measuring the extent to which light passes through the canopy. The LAI-2000 method measures the attenuation of light at five angles simultaneously. During measurement, five values ​​of the probe above the canopy and five values ​​of the probe under the canopy are obtained. The five values ​​of the canopy transmittance are obtained by dividing the corresponding readings by two. The leaf area index can be calculated based on the transmittance of the five zenith angles.
1.3.2 LI-3000 Leaf Area Meter Principle LI-3000 Leaf Area Meter uses a sensor to scan the measured leaf to determine its leaf area.
1.3.3 Principles of the regression equation The ornamental leaves of the pineapples are sword-shaped and have a regular geometric shape. There is a significant positive correlation between leaf area and leaf length, and the relationship between leaf area and length should be fixed for a particular species. Therefore, taking the square of the leaf length as the independent variable and the leaf area as the dependent variable, after establishing the regression equation of the specific species, we can use this equation to calculate the leaf area per plant based on the leaf length, and then combine the planting density to obtain the leaf area index. . The regression equation was obtained by using the data of leaf length and single leaf area for regression analysis. In this study, 30 leaves of different sizes and different ages of ornamental pineapple were randomly selected on different plants. The leaf length was measured first and then passed through the leaf shape. Paper weighing method obtained its single leaf area. The leaf paper weighing method uses the following formula to calculate the leaf area of ​​the leaf: leaf area = (1 white area x leaf shaped paper weight) / 1 white paper weight. The leaf-shaped paper weighing method is a relatively accurate but time-consuming and labor-intensive method, and its practical application is limited. The reason why this method was chosen for this study was to compare it with the LAI-2000 canopy analysis method and L I-3000 leaf area meter method.
2 Results and Analysis
2. 1 LA I-2000 Canopy Analyzer Determination Results The LAI-2000 canopy analyzer was used to determine the leaf area index results of the “New World†and “Torch†of ornamental Fenghuang pear varieties.
2. 2 LI - 3000 Determination of Leaf Area Meter The leaf area of ​​each pineapple was determined using a LI - 3000 leaf area meter. The LAI was then calculated based on the planting density. Leaf area index (LAI) = leaf area per plant (m2/plant) × planting density (plant/m2)
2. 3 Measurement Results of the Regression Equation Measurement Method
2.3.1 Obtaining Regression Equations From Figure 1 and Figure 2, we can see that there is a significant linear correlation between the square of the leaf length and the leaf area of ​​two ornamental pineapple varieties of the “New World†and “Torchâ€. For the "New World" species, the formula for calculating leaf area from leaf length is: leaf area (LA) = 0.114 2 × leaf length (L2), r2 = 0. 946 8; "Torch" species, which is calculated from leaf length The area formula is: leaf area (LA) = 0. 143 1 × leaf length square (L2), r2 = 0. 955 5.
2.3.2 Leaf area index Inferred to select 3 representative pineapple plants in the measured area and measure the leaf length of each leaf. Then use the formula obtained above to calculate the leaf area of ​​each plant and calculate the planting density. LA I (Table 3).
2. 4 Comparison of Measurement Results by 3 Measurement Methods
From Table 4, it can be seen that, in the "New World" variety, the results of the three methods have no significant difference at the level of 0.01, while the results of the "Torch" variety, the LI-3000 leaf area meter method and the other two methods are There are significant differences between 0. 05 and 0. 01 levels. In general, the results of the LI-3000 leaf area meter method were higher than the LA I-2000 canopy analyzer method and the regression equation method.
3 Conclusions and discussions
This study found that for the leaf area index of ornamental pineapples in the greenhouse, the results of the LI-3000 leaf area method were generally higher than the other two methods. In the "New World" variety, the results of the three methods were not significantly different at the 0.05 level; whereas the "Torch" variety, the LI-3000 leaf area method was determined with the other two methods at 0.05 and 0.01. There are significant differences in levels.
The LA I-2000 Canopy Analyzer method determines the canopy leaf area index based on optical principles and can be used directly for population measurements. It is very convenient to apply in large canopy analysis of many blades. Using this instrument to measure the canopy leaf area index does not need to destroy the crop itself, so it does not affect the canopy. However, because the instrument is relatively expensive, it is generally used only in scientific research units and cannot be used in production. In addition, although the operation of the instrument is not complicated, it still requires a certain amount of training and learning, and there is a relatively high level of knowledge of the operator's knowledge. Therefore, the LA I-2000 canopy analyzer method is only suitable for scientific research. The LI-3000 leaf area meter method uses the sensor to scan the measured leaf to determine its leaf area, and it is accurate and convenient to measure leaf area or leaf area per plant. Compared with the LA I-2000 canopy analyzer method, the instrument is relatively inexpensive, easy to operate, requires little training and learning, and does not require much operator requirements. Therefore, it is more practical and popular. However, the instrument is only suitable for measuring small canopies with few leaves. However, for large canopies with a large number of leaves, it is time-consuming and labor-consuming and it is almost impossible to complete. In addition, using this instrument to measure the leaf area requires the blade to be cut, so destructive sampling is required and the canopy will have a certain influence. The regression equation method is based on the geometric shape of the plant leaf and regards it as a certain geometrical figure, and uses a readily available appearance parameter such as the leaf length or leaf width to calculate the single leaf area. Using this method to determine the leaf area does not require any equipment. It requires only a ruler, and requires little extra cost, so it can be used universally in actual production. In addition, using this method, only the leaf length needs to be measured and the plant will not be damaged. The disadvantages are similar to the LI-3000 leaf area meter method, which can only be applied to small canopies, but it is almost impossible to use for large canopies.
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