Characterization of Photosynthetic Performance during Senescence in Stay-Green and Quick-Leaf-Senescence Zea mays L. Inbred Lines

Abstract

The net photosynthetic rate, chlorophyll content, chlorophyll fluorescence and 820 nm transmission were investigated to explore the behavior of the photosynthetic apparatus, including light absorption, energy transformation and the photoactivities of photosystem II (PSII) and photosystem I (PSI) during senescence in the stay-green inbred line of maize (Zea mays) Q319 and the quick-leaf-senescence inbred line of maize HZ4. The relationship between the photosynthetic performance and the decrease in chlorophyll content in the two inbred lines was also studied. Both the field and laboratory data indicated that the chlorophyll content, net photosynthetic rate, and the photoactivities of PSII and PSI decreased later and slower in Q319 than in HZ4, indicating that Q319 is a functional stay-green inbred line. In order to avoid the influence of different development stages and environmental factors on senescence, age-matched detached leaf segments from the two inbred lines were treated with ethephon under controlled conditions to induce senescence. The net photosynthetic rate, light absorption, energy transformation, the activities of PSII acceptor side and donor side and the PSI activities decreased much slower in Q319 than in HZ4 during the ethephon-induced senescence. These results suggest that the retention of light absorption, energy transformation and activity of electron transfer contribute to the extended duration of active photosynthesis in Q319. Although the chlorophyll content decreased faster in HZ4, with decrease of chlorophyll content induced by ethephon, photosynthetic performance of Q319 deteriorated much more severely than that of HZ4, indicating that, compared with Q319, HZ4 has an advantage at maintaining higher photosynthetic activity with decrease of chlorophyll although HZ4 is a quick-leaf-senescence inbred line. We conclude that attention should be paid to two favorable characteristics in breeding long duration of active photosynthesis hybrids: 1) maintaining more chlorophyll content during senescence and 2) maintaining higher photosynthetic activity during the loss of chlorophyll.

Mechanisms by which the infection of Sclerotinia sclerotiorum (Lib.) de Baryaffects the photosynthetic performance in tobacco leaves

“…Fv/Fm, ETR and qP decreased significantly in K 2 C 2 O 4 treated leaves but the NPQ increased, indicating that the activity of PSII was significantly damaged by C 2 O 4 2− .We propose that during S. sclerotiorum infection, the decreased PSII activity was probably due to the damage to the reaction centre and acceptor side of PSII by C 2 O 4 2− secreted by S. sclerotiorum because there was no difference observed in W k (an indicator of the activity of the donor side of PSII [33,34]) between K 2 C 2 O 4 treated leaves and control leaves (Additional file 2: Figure S2), and Ψ o (an indicator of electron transport at PSII acceptor side [35]) decreased in K 2 C 2 O 4 treated leaves (Additional file 3: Figure S3). In the dark, no significant difference was observed in F v /F m between K 2 C 2 O 4 treated leaves and control (Figure 4), demonstrating that C 2 O 4 2− inhibited the photosynthetic electron transfer chain in an indirect, light-dependent manner.…”

GROWTH REGULATING FACTOR5 Stimulates Arabidopsis Chloroplast Division, Photosynthesis, and Leaf Longevity

“…S4). Extending the capacity of the plant to photosynthesize and produce assimilates during later developmental stages is proposed to delay senescence (Spano et al, 2003;Zhang et al, 2012). Moreover, leaf senescence is postponed by cytokinins and could serve an additional commonality between GRF5 and cytokinin functions.…”

Systemic regulation of photosynthetic function in field-grown sorghum

“…Gas exchange was measured following the method of Zhang et al (2012) using a CIRAS-2 portable photosynthesis system (PP Systems, USA) with ambient CO 2 concentration (350e380 mmol mol À1 ), an irradiance of 1200 mmol m À2 s À1 , 80%…”