条锈菌侵染过程中小麦叶片水分关系的变化

Changes in Water Relations of Wheat Leaves in the Infection Process of Stripe Rust

以条绣菌 2 9号小种 (CY 2 9)及其弱毒突变菌系(CY2 9 mut3 )分期接种小麦幼苗一叶 ,同期对条锈菌侵染过程中亲和性反应与不亲和性反应寄主 病原组合接种叶片水分关系的变化进行测定。结果表明 ,两种组合间存在显著的差异。亲和性反应寄主病叶的主要变化如下 :(1)潜育期气孔开放受到明显抑制 ,压力势 (ΨP)轻微升高 ;(2 )显症至产孢前病叶叶片扩散阻力 (LDR)、相对含水量 (RWC)和ΨP 轻微下降 ,蒸腾速率 (Tp)逐步上升 ;(3)产孢后LDR大幅下降 ,Tp 急剧升高 ,RWC、水势 (ΨW)、ΨP和渗透势 (Ψπ)均大幅降低。不亲和反应寄主接种叶片的气孔开放在潜育期同样受到了抑制 ,在显症期接种叶Tp 轻微升高 ,LDR和ΨP 轻微下降 ,在侵染过程的后期 ,不亲和反应寄主接种叶气孔开放恢复到健叶水平 ,并保持了较低的Ψπ和较高的ΨP。显然 ,亲和性反应寄主病叶已失去了维持自身水分平衡的能力 ,而不亲和性反应寄主接种叶的水分平衡在侵染初期虽受到了轻微的干扰 。

The first leaves of wheat were inoculated with virulent race (CY29) and its avirulent mutant (CY29 mut 3) of stripe rust ( Puccinia striformis West.) at different stages of infection. Water relations at the same time in inoculated leaves of both compatible and incompatible combinations of host pathogen were compared. The results revealed remarkable differences between the two combinations. Changes in water relations in inoculated leaves of compatible combination, were as follows: (1) stomatal opening was inhibited markedly (Fig.3) and turgor potential (Ψ p ) slightly increased in incubation period (Fig.4); (2) transpiration rate (T p) increased progressively (Fig.2) with the decrease of leaf diffusive resistance (LDR), relative water content (RWC) and Ψ p from the appearance of rust symptom to the formation of fungal uredia; (3) LDR decreased greatly (Fig.3) and T p increased significantly (Fig.2) accompanied by lower values of RWC (Fig.1), Ψ p, water potential (Ψ w ) and osmotic potential (Ψ π) (Fig.4) after fungal sporulation. It was important that inhibition of stomatal opening in incubation period, and slight increase in T p and slight decrease in LDR and Ψ p around the time of symptom appearance, and then higher Ψ p and lower Ψ π after necroses of diseased tissue at the later stage of infection process (Fig.4) were observed in wheat leaves of incompatible combination. It was obvious that infected leaves of compatible combination lost their ability to maintain normal water balance. On the other hand, water balance in leaves of incompatible combination was disturbed slightly at the beginning of infection and then returned to its normal state.