Patterns of Chlorophyll Fluorescence Kinetics in Relation to Growth and Expansion in Cucumber Leaves

Abstract

MATERIALS AND METHODSPhotochemical development was studied in developing cucumber (Cucumis sativus L. cv Hokushin) leaves to determine if the spatial pattern coincided with relative growth rates of expanding leaves, intercalary cell division, or position relative to the vascular tissue. Both leaf surfaces undergo a series of similar changes in chlorophyll a fluorescence kinetics, but the upper surface more quickly achieved the characteristic response. Imaging of fluorescence showed an individual developing leaf has four regions differing in kinetics, but these regions do not coincide with areas of increasing relative growth rate. Two of these regions lie at the leaf edge and their divergent kinetics may be related to structural and physiological features present at this position. A third area with different kinetics, in the basal region of the leaf, is spatially consistent with primordial regions that are clonal during development. The correspondence between areas of clonal growth and specific fluorescence kinetics indicates that cells of common ancestry show functional uniformity. No evidence was found that the proximity of the vascular tissue influenced development of photochemical function.The attainment of photosynthetic competency in angiosperm leaves is regulated by light and by developmental factors. Unlike monocots such as wheat (2), cucumber leaves are not photochemically competent when first exposed to light, but acquire competency over an extended time period, 6 d or more in the light (5). Within these leaves photochemical activity is not homogeneous, but develops basipetally as shown by Chl a fluorescence transients. These data indicate that the primary regulation ofthe development ofphotochemical activity lies with developmental factors, not light (5).Although the attainment of characteristic fluorescence transients progresses in a basipetal direction, mirroring the general direction ofexpansion and growth ofthe leaf(5), the influence of developmental factors from cells and tissues within the leaves has not been studied. The objective of the present research was to determine ifthe spatial pattern of photochemical development coincided with leaf expansion and relative growth rates, intercalary cell division, or position relative to the vascular tissue. With the availability of dynamic imaging of Chl a fluorescence (10), a precise, nondestructive means of studying these influences exists.'Supported by a National Science Foundation grant (JGC). Plant Materials and Leaf Area MeasurementsCucumber (Cucumis sativus L. cv Hokushin) plants were grown as previously described (10) for up to 5 weeks. For fluorescence and gas exchange measurements, plants were brought from the controlled-environment greenhouse to the laboratory and allowed to acclimate for about 2 h. Plants were dark-incubated for at least 30 min before fluorescence induction. No appreciable differences in induction kinetics were observed with longer dark periods. Leaves monitored for fluorescence and assimilation were intact and remain...

Spatio‐temporal heterogeneity in Arabidopsis thaliana leaves under drought stress

“…The non‐uniform photosynthetic pattern of A. thaliana leaves under drought stress may reflect different zones of the leaf anatomy and mesophyll development. The observed gradient of heterogeneity in chl fluorescence patterns between the leaf base and the tip is in accordance with the findings of Croxdale & Omasa (1990), Loreto & Sharkey (1990) and Meng et al. (2001).…”

“…2010). Croxdale & Omasa (1990) observed a basipetal progression ( i.e ., from tip to base of the leaf) in acquisition of the characteristic phases of fluorescence induction, and concluded that the resulting mosaic of photochemical activities indicates that cells of common ancestry show functional uniformity. Age‐specific differences in plant responses to drought stress have been reported for Olea europaea and A. thaliana leaves by Loreto & Sharkey (1990) and Jung (2004), respectively.…”

Sink–source transition in tobacco leaves visualized using chlorophyll fluorescence imaging

“…It can also be used to analyse photosynthetic flux and control of fluxes by metabolic processes in leaves (Weis & Berry, 1987;Genty et al , 1989;Weis & Lechtenberg, 1989;Krause & Weis, 1991). Kinetics of chlorophyll fluorescence have previously been imaged in developing cucumber leaves (Croxdale & Omasa, 1990). Recently, camera based systems for chlorophyll a fluorescence imaging have been developed which are capable of visualizing the distribution of the quantum efficiency of PSII ( Φ PSII ) throughout a leaf.…”

A Comparison of Three Isolines of Cotton Differing in Fiber Color for Yield, Quality, and Photosynthesis

“…Photosynthetic efficiency could aff ect the yield and quality of many crops, including cotton (Reddy and Zhao, 2005;Dordas and Sioulas, 2008;Liu et al, 2008). This might partially result from its higher chlorophyll content because the function of chlorophyll in plant leaves is to capture sunlight and to transfer the light energy into other forms of energy (Davis et al, 1979;Croxdale and Omasa, 1990;Terao and Katoh, 1996). The chlorophyll content in the GFC plant leaves generally maintained the highest level.…”