Physiological and biochemical changes in shoots of coconut palms affected by lethal yellowing

Abstract

SUMMARYNoon stomatal conductance of lethal-yellowing (LY) affected coconut palms (Cocos nucifera L. Atlantic Tall ecotype) decreased progressively as the disease developed. In the early stages of the disease and before leaf yellowing started, stomatal conductance decreased to a minimum in leaves at both the top, the middle and the base of the crown. Since altered stomatal behaviour might affect gas exchange and related processes in the plant, such as water movement and photosynthesis, these results support the hypothesis that LY-induced stomatai closure is central to the development of LY symptoms in coconut palms, and therefore to the mode of pathogenicity of the LY mycoplasma-like organism. Leaf yellowing occurred simultaneously with a decrease in photosynthetic rates and a decrease in protein, chlorophyll and carotenoid contents. Based on these biochemical changes a second hypothesis is proposed, that LY-associated leaf 3'ellowing is part of a leaf senescence process. The concentration of abscisic acid in the leaves and the capacity of leaf tissue to form ethylene increased in diseased palms, suggesting that a hormonal imbalance occurs in LY-afTected palms. Furthermore, treatment of symptomless palms with an ethylene-releasing agent (ethephon) resulted in symptoms that mimicked some of the LY symptoms. A third hypothesis is therefore proposed, that a hormonal imbalance might be related to LY symptom development, at least with respect to nutfall and leaf senescence.

ABA Increases Susceptibility of Pepper Fruits to Infection of Anthracnose by Collectotrichum acutatum

“…The concentration of ABA in the leaves and the capacity of leaf tissue to form ethylene increased in affected palms, suggesting that a hormone imbalance occurred in diseased palms (León et al, 1996). Furthermore, treatment of healthy palms with an ethylenereleasing agent (ethephon) resulted in symptoms that mimicked some of the leaf yellowing of LY symptoms.…”

Changes in photosynthetic pigment and carbohydrate content in common bean cultivars infected by Colletotrichum lindemuthianum

“…The main symptoms of this disease can be found in pods and leaves with necrosis (Kimati et al 2005). Results obtained by Lopes and Berger (2001) working with P. vulgaris, as well as Leon et al (1996) and Scarpari et al (2005) revealed changes in photosynthetic pigments after pathogen infection in susceptible plants. The accumulation of carbohydrates under conditions of biotic and abiotic stress are described by Maust et al (2003) and Lobato et al (2008a).…”

Karakterisasi Fitoplasma Penyebab Penyakit Layu Kelapa Di Pulau Derawan Menggunakan RFLP in Silico

“…Gejala akhir penyakit ini adalah mengeringnya seluruh pelepah dan daun kelapa rontok dan terlihat hanya seperti tonggak batang kayu. Menurut Leon et al (1996), tanaman yang sakit akan menghasilkan asam absisat dan etilen yang sangat tinggi. Akibatnya terjadi ketidak-seimbangan hormon yang akan memacu penuaan daun dan mengakibatkan patahnya pelepah serta gugurnya buah yang masih muda (Musetti, 2010).…”