Accumulation of End Products in Source Leaves Affects Photosynthetic Rate in Peach via Alteration of Stomatal Conductance and Photosynthetic Efficiency

Abstract

<jats:p>In ‘Beijing 24’ peach [<jats:italic>Prunus persica</jats:italic> (L.) Batch] trees, a series of source leaves with differing levels of end products were created by retaining fruit (“+fruit”), removing fruit (“−fruit”), or reducing the light period. To alter the light period, leaves were covered with a bag made of brown inner paper and outer silver paper, which was then removed at different times the next day. The highest level of end products were obtained by fruit removal, while reducing the light period resulted in a lower level than “+fruit.” Net photosynthetic rate (P<jats:sub>n</jats:sub>) and stomatal conductance (<jats:italic>g</jats:italic><jats:sub>s</jats:sub>) decreased, but leaf temperatures (T<jats:sub>leaf</jats:sub>) increased, following an increase in end product levels in leaves. After the “−fruit” treatment, reduced P<jats:sub>n</jats:sub> was correlated with lower <jats:italic>g</jats:italic><jats:sub>s</jats:sub>, and T<jats:sub>leaf</jats:sub> increase was concomitant with decreases in maximal quantum yield of photosystem II (F<jats:sub>v</jats:sub>/F<jats:sub>m</jats:sub>), actual photochemical efficiency of photosystem II (ΦPSII), and photochemical quenching, and with an increase in nonphotochemical quenching. However, there were no significant differences in chlorophyll fluorescence between “+fruit” and the two treatments reducing the light period. The ΦPSII decreased following an increase in foliar sorbitol level, and it linearly decreased as sucrose and starch increased. Although fruit removal resulted in a significant accumulation of sucrose, sorbitol, and starch in leaves throughout the day, the extractable activities of several important enzymes involved in carbohydrate leaf storage and translocation did not decrease. Therefore, instead of feedback regulation by the accumulation of end products in source leaves, a high T<jats:sub>leaf</jats:sub> induced by decreased stomatal aperture may play a key role in regulation of photosynthesis by limiting the photochemical efficiency of the PSII reaction centers under high levels of the end products in peach leaves.</jats:p>

The Evaluation of Growth Performance, Photosynthetic Capacity, and Primary and Secondary Metabolite Content of Leaf Lettuce Grown under Limited Irradiation of Blue and Red LED Light in an Urban Plant Factory

“…Lettuce plants might have low sink demand owing to low developmental progress at later growth stages. This hypothesis is supported by Cheng et al [60], who found lower carbohydrate contents at later growth stages in peach.…”

“…In the current study, the starch concentration was higher at 20 DAT, whilst the concentration of soluble sugars had a declining trend at 20 DAT (Figure 4). Cheng et al [60] noticed that plant sourcesink relationships influence the carbohydrate allocation during plant growth. Sucrose is the primary carbohydrate that is translocated from source to sink tissues.…”

“…4.6 ± 0.9c 6.0 ± 0.9b 2.5 ± 0.5a 2.0 ± 0.5b 7.1 ± 1.3b 8.1 ± 1.4b 1.8 ± 0.2b 3.0 ± 0.4a 1.9 ± 0.4c 1.5 ± 0.2b B/R = 1:5 4.5 ± 0.4c 4.8 ± 1.5b 2.3 ± 0.4a 1.8 ± 0.9b 6.8 ± 0.7b 6.6 ± 2.4b 1.9 ± 0.b 2.8 ± 0.6ab 1.7 ± 0.2c 1.6 ± 0.9b In the current study, the starch concentration was higher at 20 DAT, whilst the concentration of soluble sugars had a declining trend at 20 DAT (Figure 4). Cheng et al [60] noticed that plant source-sink relationships influence the carbohydrate allocation during plant growth. Sucrose is the primary carbohydrate that is translocated from source to sink tissues.…”

Response of Bean (Vicia faba L.) Plants to Low Sink Demand by Measuring the Gas Exchange Rates and Chlorophyll a Fluorescence Kinetics

“…However, other studies, including our study on peaches and apples did not show a relationship between assimilate accumulation and the reduction of net photosynthetic rate ( P n ) under low sink demand [4], [6]–[8], [11], [15]. The mechanism by which low sink demand affects photosynthesis is still unclear.…”

Constitutive expression of cell wall invertase genes increases grain yield and starch content in maize

“…Generally, low sugar status enhances photosynthesis, reserve mobilization and export, whereas high sugar content promotes growth and carbohydrate storage (Koch, 1996;Roll et al, 2002). In peach, removing fruit from tree increased the level of end products of photosynthesis and decreased the net photosynthetic rate (P n ), maximal quantum yield of photosystem II (Fv/Fm) and actual photochemical efficiency of photosystem II (FPSII) (Cheng et al, 2009). Therefore, the initial cleavage of sucrose in sink organs plays an important role in carbon partitioning and allocation.…”