Watt Michelle, Kirkegaard John A, Rebetzke Gregory J
CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.
Funct Plant Biol. 2005 Sep;32(8):695-706. doi: 10.1071/FP05026.
Conventional wheat (Triticum aestivum L.) cultivars grow slowly in unploughed soil because of physical and biological constraints. Here a conventional cultivar (Janz) is compared with a novel experimental line (Vigour 18), bred for high leaf vigour, to explore the hypothesis that a vigorous wheat grows better in unploughed soil. Roots of both genotypes in unploughed soil were three times more distorted with 30% shorter apices and 60% shorter expansion zones than roots in ploughed soil, because of voids between blocky peds and packed sand particles that impeded root apices. More than half the root length contacted dead, remnant roots. Vigour 18 roots grew 39% faster, were thicker and distorted less than Janz roots in unploughed soil, but developed similarly in ploughed soil. Vigour 18 shoots grew 64% faster in unploughed soil, but 15% faster in ploughed soil. Fumigation of unploughed soil improved the growth of Janz only. We suggest that faster root growth, different exudates promoting a more beneficial rhizosphere microflora, or modified shoot responses are possible mechanisms to explain Vigour 18's superior growth. Vigorous genotypes may present a new opportunity for increased productivity with conservation farming.
由于物理和生物限制，传统小麦（普通小麦）品种在未耕土壤中生长缓慢。在此，将一个传统品种（扬兹）与一个为高叶活力培育的新型试验品系（活力18）进行比较，以探究活力旺盛的小麦在未耕土壤中生长更好这一假设。由于块状土粒间的空隙和紧实的沙粒阻碍了根尖，未耕土壤中两种基因型的根比耕过土壤中的根扭曲程度大三倍，根尖短30%，伸长区短60%。超过一半的根长与死亡的残留根接触。在未耕土壤中，活力18的根生长速度比扬兹的根快39%，更粗壮，扭曲程度更小，但在耕过的土壤中发育情况相似。在未耕土壤中，活力18的地上部分生长速度快64%，但在耕过的土壤中快15%。对未耕土壤进行熏蒸仅改善了扬兹的生长。我们认为，更快的根系生长、促进更有益根际微生物群落的不同分泌物或改良的地上部分反应可能是解释活力18生长优势的机制。活力旺盛的基因型可能为保护性耕作提高生产力带来新机遇。
