Increased photosynthesis and resistance to rust infection in upper, uninfected leaves of rusted broad bean (Vicia faba L.)

Abstract

SUMMARYPhotosynthesis and resistance to rust infection were studied in upper, uninfected leaves of broad bean, Vicia faba L., where the lower two leaves were infected with rust, Uromyces viciae-fabae (Pers.) Shroet. Following inoculation of the lower leaves, rates of net photosynthesis were significantiy increased in the upper, uninfected, fully-developed leaves and the young developing leaves, compared to controls. In contrast, photosynthesis was substantially reduced in the lower, rusted leaves. When '*CO,, was fed to the upper, uninfected leaves of rusted plants, there was a considerable increase in labeJIed assimilate in those leaves, compared to controls. In addition, there was substantial movement of labelled assimilate into lower, rusted leaves, into young, developing leaves and into roots. On the other hand, there was a substantial reduction in labelled assimilates moving into shoot apices.Upper, uninfected leaves of rusted beans exhibited Increased resistance to rust infection. Thus, the percentage leaf area covered with rust and the number of pustules per cm^ were reduced in these leaves compared to controls. This resistance to rust infection was greatest when the upper leaves were challenged 1 d after inoculation of the lower leaves with rust and decreased with increasing time after inoculation of the lower leaves. Young, developing leaves on rusted beans also exhibited increased resistance to rust infection. When photosynthesis in the upper leaves was reduced to near control values or well below control values by shading, resistance to rust infection in those leaves was also reduced, although not in proportion to the reduction in photosynthesis. It is suggested tbat the increased photosynthesis in upper, uninfected bean leaves probably facilitates maximum expression of resistance to infection in those leaves.

Effect of several rhizobacteria strains on barley resistance againstPyrenophora gramineaunder field conditions

“…The data presented here suggest that either the plants possessed suffi cient resources to support both growth and defense, or they use resources diverted from growth to defense. This phenomenon has been reported by several workers (Murray and Walters, 1992;Ziadi et al, 2001;Prats et al, 2002;Cór-dova-Campos et al, 2012). A number of hypotheses have been put forth to explain how plants reallocate resources during the induction of plant defenses and how induced resistance benefi ts the overall fi tness of the plant relatively to constitutive defense mechanisms (Ahmad et al, 2010;Cór-dova-Campos et al, 2012).…”

Functional significance of triazine-herbicide resistance in defence of Senecio vulgaris against a rust fungus

“…We found no compensatory increase in photosynthesis once our measured values of whole-plant photosynthesis were adjusted to reflect photosynthesis per unit leaf area. This is in contrast to the findings of Murray and Walters (1992) studying rust infection on Vicia faba L., but they directly used measurements of individual leaves and found compensation in non-infected leaves of infected plants. Our measurement of whole-plant photosynthesis integrates leaves which may have reduced photosynthesis, with those that may have increased levels of photosynthesis, and we could therefore be masking compensation in uninfected tissue by using this approach.…”

Sink‐stimulated photosynthesis and sink‐dependent increase in nitrate uptake: nitrogen and carbon relations of the parasitic association Cuscuta reflexa–Ricinus communis

“…Parasite-related stimulation of photosynthesis has also been found in the dwarf mistletoe Arceuthobium (Clark & Bonga 1970), in uninfected leaves of rust-infected plants (Livne 1964;Murray & Walters 1992) and, interestingly, also in the association Striga-Sorghuni, but only during early stages of parasite (and host) development (Cechin & Press 1993). This stimulation occurred at limiting N supply to the host only, and thus may be directly compared to the present findings.…”