Morphological responses of Navelate orange tree grafted on different rootstocks under water deficit

Abstract

Conditions of water deficit can cause morphological changes in plants which consequently affect physiological processes and interfere with plant metabolism. As grafting is a standard process used for citrus trees, these changes depend on the rootstock used and its interaction with the scion; this interaction will determine which plant has the best performance. This study involved assessment of changes in DNA and chlorophyll A and B content in Navelate orange seedlings grafted onto five different rootstocks (Indian and San Diego citrandarin, Swingle citrumelo, Santa Cruz Rangpur lime and Sunki mandarin) under conditions of water deficit. The seedlings from the respective combinations were approximately 12 months-old when they were transferred to 5 L polyethylene bags filled with substrate, comprising standard soil and sand at a 3:1 ratio. Plants were maintained in a greenhouse for three months. After this period, the experiment was set up using a randomized block design with a 5x2x5 factorial scheme based on the following: five rootstocks with and without irrigation, and time-points at 25, 29, 32, 35 and 38 d after stopping irrigation. At each of these time-points, chlorophyll content was assessed by direct reading in cloroLOG CFL1030 equipment and also the DNA content was determined using flow cytometry. The results suggest that severe water deficit can cause morphological changes in DNA content and in chlorophyll concentration, and that the changes are most marked with Sand Diego and Swingle rootstocks. Index terms: flow cytometry, chlorophyll content. Respostas morfológicas da laranjeira Navelate enxertada em diferentes porta-enxertos e sob déficit hídrico RESUMOAs condições de déficit hídrico podem causar alterações morfológicas em plantas que consequentemente afetam os processos fisiológicos e interferem em seu metabolismo. Essas mudanças dependem do porta-enxerto usado e sua relação com a copa uma vez que a enxertia é um processo padrão usado na formação das plantas cítricas. Este estudo teve como objetivo identificar o melhor desempenho da interação de diferentes porta-enxertos com a copa Navelate em condições de estresse hídrico; mediante avaliação do conteúdo de DNA e clorofila A e B. Foram estudados os portaenxertos citrandarin Indio e San Diego, citrumelo Swingle, limão Cravo Santa Cruz e tangerina Sunki