Controlled Humidification of Sweet Potato Stem-Cuttings in a Self-Sustaining Humidifier: Effects on Vigour, and Implications for Climate Change

Mark Anglin Harris

doi:10.5539/jas.v7n8p175

Abstract

Predictions of extreme weather associated with global warming signify potential extremes in soil water content, and extremes of soil water tension are inimical to early plant growth. Periderm tissue [cork cells], being waterproof, restricts root and stem waterlogging whilst the promotion of early roots better prepare stem cuttings for survival in dry soils. Sweet potato stem cuttings were stored for up to six days in a chamber humidifier. Humidification was achieved by evaporation up to saturation vapour pressure [SVP] in a closed system of capillary water evaporating from a fabric which enclosed the cuttings. Treatments included vine cuttings stored (1) under grass clippings (traditional treatment) and (2) inside a high humidity (100%) chamber. Root growth occurred on 90% of the cuttings in the root length sequence: 9-, 28-, 47 mm after 3, 6 and 9 days respectively in the 100% humidity chamber at an average ambient room temperature of 25 oC. Under traditional treatments, root growth occurred on only 10% of the cuttings and was 0.5-, 2-, and 3 mm after 3, 6 and 9 days respectively. Traditional treatment did not exhibit observable periderm (cork cells) growth at any stage of the study. Periderm thicknesses of 3-, 7-, and 9mm occurred on days 3, 6, and 9 for samples held at 100% humidity. No periderm was observed for the traditionally treated samples. For field trials, the most vigorous growth in a dry soil was observed for cuttings previously subjected to chamber humidification, an important asset when early season weed competition is evident and when rapid ground cover is important. In a broader perspective, these results can be used to optimize studies of other crops grown from cuttings.

Highlights

1.1 Propagation Problems in Dry SoilsA lack of roots in dry soils causes wilting and desiccation of vine cuttings, but an evenly moist soil provides the best environment for root initiation and development (Meyers et al, 2014)
Humidification was achieved by evaporation up to saturation vapour pressure [SVP] in a closed system of capillary water evaporating from a fabric which enclosed the cuttings
The main methods of propagation of sweet potato are (1) shoots developed from the vascular cambium and emerging through the cortex of the root, the shoots developing adventitious roots and becoming small plants attached to the seed root, and (2) vine cuttings which produce adventitious roots

Summary

Introduction

A lack of roots in dry soils causes wilting and desiccation of vine cuttings, but an evenly moist soil provides the best environment for root initiation and development (Meyers et al, 2014). The main methods of propagation of sweet potato are (1) shoots developed from the vascular cambium and emerging through the cortex of the root, the shoots developing adventitious roots and becoming small plants attached to the seed root, and (2) vine cuttings which produce adventitious roots. For propagating the sweet potato, vine cuttings are advantageous in that they do not transfer soil borne diseases and nematodes as do sprouts with roots (Yamaguchi, 1983). The use of sprouts has been discouraged as a general practice because yields are lower compared to those from vine cuttings (Ikemoto, 1971)

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