Métodos indiretos de estimativa do índice de área do cladódio da palma forrageira e sua relação com as características morfogênicas e produtivas

Abstract

The leaf area index (LAI) is a fundamental information on investigation of the ecological adaptation of individuals to new environments and crucial in assessing the effects of the management on crop yield. This, the accuracy of the measurement of LAI is critical. There are several indirect methods that are used for this purpose, in order to facilitate the collection of data in the field. However many are onerous and, or, crafty, why the need to be analysed individually. The modelling method, by requiring less entry information, appears as an alternative of simplification in obtaining these data. The LAI depends on morphogenetic features of plants, and makes the crop productivity. Therefore, the objective of this work was to evaluate the use of indirect methods of measurement of cladode area index (CAI) of forage cactus for the evaluation of the relationship of the IAC with morphogenetic features and productive. The experimental data were collected in a Germplasm Active Bank (GAB) located at the Instituto Agronômico de Pernambuco - IPA, in Serra Talhada. In 180 plants of three clones (IPA Sertânia, Miúda and Orelha de Elefante Mexicana) morphogenesis and biomass data were recorded. The techniques of estimative of the CAI were evaluated in relation to the digital method (reference). The Indirect methods used were: the method of light interception (ceptômetro-AccuPAR, LP-80, Decagon Devices, Pullman, USA) and its derivations with regard to obtaining the measurement format within the sub-area experimental, foliar discs of medium cladode, planimetric method of medium cladode, and modelling method based on plant total morphogenesis, plant representative ramification morphogenesis and medium cladode morphogenesis. The performance of methods was reviewed by statistical indexes and errors, and with Student's t-test at 5% of significance (p > 5%). In the analyze of the contribution of the morphogenetic features about the IAC, and this on the crop yield was used in the path analysis. The ceptometer, planimetric and specific leaf area methods are not recommended for the estimation of the forage cactus IAC Palm. The use of the method of modeling obtained better performance compared to other indirect methods. In turn, the IAC and cladode total number can be used as indicative crop productive response to environment, i.e. the morphogenetic features of the plant are crucial in definition of the forage cactus clones IAC.