Costa Pinto Luciana Santos Rodrigues, Azevedo João Lúcio, Pereira José Odair, Carneiro Vieira Maria Lúcia, Labate Carlos Alberto
1 Departamento de Genética, Escola Superior de Agricultura 'Luiz de Queiroz',Universidade de São Pálo, Av. Pádua Dias n° 11, CP 83, CEP 13400-970, Piracicaba-SP, Brazil.
New Phytol. 2000 Sep;147(3):609-615. doi: 10.1046/j.1469-8137.2000.00722.x.
Very little is known about the physiological interactions between plant hosts and symptomless endophytic fungi despite their widespread occurrence. We investigated the impact of two such fungi, Colletotrichum musae and Fusarium moniliforme, upon the photosynthetic capacity of two crop plants, banana and maize, respectively. Endophyte-free plants were obtained first and then infected with the fungi. Measurements of total chlorophyll content revealed very little difference between endophyte-free and infected plants of banana, whereas in maize they showed 50% reductions in the endophyte-infected plants. The maximum photochemical capacity (F /F ) was measured in order to determine if the plants had any photoinhibitory effect caused by biotic or abiotic factors. After 45 d of growth, endophyte-free banana plants had similar values of F /F to plants typical of nonstressed conditions, whereas the endophyte-infected plants showed a reduction of approx. 15%. Unlike banana, infected maize plants displayed values of F /F similar to those of control and endophyte-free plants, indicating that the maximum photochemical capacity was not affected by infection. The light response curves of both species showed that the photosynthethic capacity was severely reduced in endophyte-infected plants, reaching saturation at c. 400 μmol m s whereas the control and endophyte-free plants were saturated at much higher photon flux densities. In banana the effect seemed to be due to an impairment of electron transport in the thylakoid membranes. By contrast, reduction of the photosynthetic capacity in maize was due to a reduction in chlorophyll content, leading to a decrease in the electron transport components and a consequent reduction in carbohydrate synthesis. It is possible that the reduction in the maximum yield of photosynthesis in both crops was caused by toxins produced by the fungi. Nevertheless there were no major macroscopic effects on the plants to indicate disease symptoms.
尽管无症状内生真菌广泛存在，但人们对植物宿主与它们之间的生理相互作用却知之甚少。我们分别研究了两种这样的真菌——香蕉炭疽菌和串珠镰刀菌对两种作物香蕉和玉米光合能力的影响。首先获得无菌植物，然后用这些真菌进行感染。总叶绿素含量的测量结果显示，香蕉的无菌植物和感染植物之间差异很小，而在玉米中，感染内生真菌的植物叶绿素含量降低了50%。测量最大光化学能力（F /F ）以确定植物是否受到生物或非生物因素引起的光抑制作用。生长45天后，无菌香蕉植物的F /F 值与非胁迫条件下的典型植物相似，而感染内生真菌的植物F /F 值降低了约15%。与香蕉不同，感染内生真菌的玉米植物的F /F 值与对照和无菌植物相似，这表明最大光化学能力不受感染影响。两个物种的光响应曲线均表明，感染内生真菌的植物光合能力严重降低，在约400 μmol m s 时达到饱和，而对照和无菌植物在高得多的光子通量密度下才达到饱和。在香蕉中，这种影响似乎是由于类囊体膜中电子传递受损。相比之下，玉米光合能力的降低是由于叶绿素含量减少，导致电子传递成分减少，进而碳水化合物合成减少。两种作物光合作用最大产量的降低可能是由真菌产生的毒素引起的。然而，对植物没有明显的宏观影响表明出现病害症状。
