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Update:July 31, 2020

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Dry treatment of container-grown seedlings of Japanese cedar increases their tolerance to drought

Article title

Drought hardening contributes to the maintenance of proportions of non-embolized xylem and cambium status during consecutive dry treatment in container-grown seedlings of Japanese cedar (Cryptomeria japonica)

Author (affiliation)

Shin-Taro Saiki (a), Yuho Ando (b), Kenichi Yazaki (a), Hiroyuki Tobita (a)

(a) Department of Plant Ecology, FFPRI, Tsukuba, Ibaraki, Japan.

(b) Department of Mushroom Science and Forest Microbiology, FFPRI, Tsukuba, Ibaraki, Japan.

Publication Journal

Forests, 11(4), 441, April 2020 DOI:10.3390/f11040441( External link )

Content introduction

The greatest proportion of weather-related damage to young trees in Japan is caused by soil dryness, which accounts for about 40% of such damage over a 5-year period after planting. In addition, attempts have been made to even out workload during the year using container-grown seedlings at forestry sites. At the same time, the planting of seedlings has tended to increase during periods when the soil is dry. Therefore, in order to reduce seedling death caused by dry soil, our research has examined this from the perspective of "determining whether or not seedling tolerance to soil dryness can be improved by 'drought hardening', that is, by subjecting Japanese cedar seedlings to dry soil beforehand by growing them in containers under drought conditions before planting".

Seedlings that were subjected to drought hardening were able to use water in their soil sparingly via lowered their transpiration (that is, they reduced the amount of water that is lost through their leaves). Such changes enabled them to conserve water in their trunks for long periods, even when watering was stopped and the soil was dried, and even their cells were able to maintain normal conditions (Fig.). In this way, we could see that drought hardening by reducing the watering of Japanese cedar seedlings helped them to acquire properties that enabled them to increase their tolerance to soil dryness. The results of this study will contribute to the development of techniques for container-growing of seedlings to make them highly tolerance to drought stress.


Fig. Photos of electron microscope observations

Fig. Photos of electron microscope observations of frozen samples taken near the ground from the trunks of seedlings grown in containers at 13 days after watering was stopped. Water has drained from the areas that appear black. Compared with the control sample, the sample subjected to drought hardening treatment has fewer black areas, and there is less deformity of its cells. Therefore, it appears that the cells whose water was better retained were in a healthy condition. The length of the scales is 100µm.

Figures from the published paper were used with some modifications.

Abbreviations: Ca = cambium; Ph = secondary phloem; Xy = xylem.