Influence of root zone calcium on potato tuberization, shoot growth and tuber quality

Ca is known to play a crucial role in plant growth and development because of its well known effects on the maintenance of cell membrane and cell wall structure and acting as a signaling molecule. Recent studies have documented the beneficial effects of Ca addition on potato tuber quality and mitigation of environmental stress. Studies reported herein provide evidence that potato tuber number, shoot growth and maintenance of apical dominance are influenced by root zone Ca. The present studies were undertaken to investigate: (i) the influence of root zone Ca concentrations on potato tuberization; (ii) influence of the range of root zone Ca concentrations on the growth of the potato apical shoot apex and on the maintenance of apical dominance in sterilized microculture; (iii) the potential for enhancing tuber Ca content and reduce internal physiological defects by the application of soluble forms of Ca and N during tuber bulking under field conditions. Our results suggest that soil Ca can alter tuberization. Application of Ca reduced tuber number and increased tuber size suggesting that soil Ca level can alter tuberization signal. Evidence was found to support of the hypothesis that high root zone Ca levels are required for tissue culture plantlets to maintain apical dominance. Lack of Ca in the shoot tip causes collapse of the cells in the sub-apical region thereby compromising the growth of shoot apex. Evidence in support these results were found by inhibiting Ca uptake in media by EGTA and by tracking Ca transport using 45Ca in the root media. It appears that potato shoot tip growth is modulated by insitu Ca concentration in the growing tip rather then by a secondary signal induced by Ca in the root. Field applications of soluble Ca during tuber bulking period resulted in a significant increase in tuber Ca concentration and appear to reduce incidence of internal physiological defects such as internal brown spots. Seasonal differences in this response suggest that in some season factors other than Ca was determine the incidence of internal defects.