Circadian rhythm of stem and fruit diameter dynamics of Japanesepersimmon (Diospyrus kaki Thunb.) is affected by deficiency of water in saline environments

Abstract

Early diagnosis of water deficiency is essential to mitigate salt stress injury in plants. The effects of salt stress during the fruit growth stage on stem and fruit diameters of Japanese persimmon trees (Diospyrus kaki Thunb.) were measured by a micromorphometric technique under greenhouse conditions. This technique is less cumbersome and more precise in comparison to measurement of water potential in a small pressure chamber. The effect of stress was measured on photosynthetic rate, pre-dawn water potential, stomatal conductance, transpiration and Na+ and K+ contents of the stem and leaves. Salt stress was imposed by irrigating the plants with NaCl solution. Stem and fruit diameters of the plants given the control treatment started to decrease around 0600 h and reached a minimum at 1400 h. Salt stress did not change the diurnal pattern of response in stem and fruit diameter dynamics, but decreased the amplitude of the circadian rhythm by influencing both declining and recovery phases. The effect of salt stress on stem diameter appeared after 1 d of treatment, and on the third day in the fruit. Salt stress also reduced water potential, photosynthesis, transpiration and stomatal conductance, and increased concentrations of Na and K in the plant parts. Most of these effects were expressed after a lag period of 5 d of salt application. Utilization of micromorphometric techniques for early diagnosis of water deficiency in salt-prone environments is recommended based on results of this study.

Differences in the responses of stem diameter and pod thickness to drought stress during the grain filling stage in soybean plants

“…Night-time closure of the stomata improved water potential and encouraged assimilate partitioning into the fruits. This is consistent with the results of Ito et al (2002) in Japanese pear, Fujita et al (2003a) in Japanese persimmon, and Moghaieb et al (2006) in tobacco, in which fluctuations in the circadian rhythm of stem diameter and pod thickness was mainly regulated by the water status.…”

“…The night recovery of pod thickness continued to decrease with the passage of time because the organ failed to gain water under stressed conditions. The correlations between circadian rhythm changes in stem and fruit diameters and water potential of the organs were recorded previously in tomato (Johnson et al 1992, Fujita et al 2003a. It was suggested that low water potential of the plant during the daytime reduced phloem turgor and thereby decreased the driving force for sap flow into the fruit.…”

“…Changes in the stem diameter and pod thickness were recorded at 5 min intervals during 13 days stress treatment after the initiation of the stress treatment in both the control and stress conditions using a micro-displacement detector according to the method described previously by Fujita et al (2003a). The point of measurement of the stem diameter was 10 cm from the base of the main stem.…”

Growth and Photosynthetic Response of Two Persimmon Rootstocks (<i>Diospyros kaki</i> and <i>D. virginiana</i>) under Different Salinity Levels

“…3D). Similar observations were also determined by Fujita et al (2003) who reported that leaf gas exchange parameters of D. kaki were significantly reduced under salinity stress. Salinity affects plant growth due to changes in many physiological processes including photosynthesis (Kalaji and Pietkiewicz, 1993;Kalaji and Guo, 2008).…”

“…Besides there are only few studies carried out to determine the response of persimmon rootstocks to salinity stress by assessing gas exchange, to our knowledge. Fujita et al (2003) measured the effects of salinity stress on photosynthetic rate, pre-dawn water potential, stomatal conductance, transpiration and Na and K contents of D. kaki leaves. The author indicated that salt stress reduced water potential, photosynthesis, transpiration and stomatal conductance.…”