Subcrown Internodes Research Articles

Resistance to common root rot (Cochliobolur sativus) in wheat in Queensland

The field resistance to common root rot (Cochliobolus sativus) of wheat lines, graded for their reaction to this disease in Canada, was determined under Queensland conditions. Several Australian varieties were also examined. Lines considered resistant and susceptible in Canada behaved in a similar fashion under Queensland conditions, while Australian varieties were generally intermediate. Discolouration of the sub-crown internode was the commonest symptom of the disease and was associated generally with a decrease in individual plant yield and in the number of heads on each plant. Discolouration of the sub-crown internode associated with Pyrenochaeta sp. in one experiment gave a varietal reaction pattern similar to that obtained with C. sativus at other sites. There appears little relationship between varietal reaction to common root rot and that previous1 reported to crown rot (Gibberella zeae).

Culm Length and Differential Development of the Coleoptile, Root, and Subcrown Internode of Near‐Isogenic Wheat Lines1

Five near‐isogenic selections of winter wheat that differ in culm length and the two parental varieties were studied to compare morphohistological development of some seedling characters and to relate the developmental differences to culm length phenotype and genotype. Coleoptile length, subcrown internode length, seedling emergence rate index, total seedling emergence, and culm length were shown to be positively interrelated in most selections. Differential development of coleoptile and subcrown internode length depended generally upon differential enlargement of their parenchyma cells. The single exception to this occurred in Selection 9 where an increased rate of cell division was associated with coleoptile development, but a shortened subcrown internode was attributed to a decreased rate of cell division. On the other hand, parenchyma cell width of neither coleoptile nor subcrown internode showed any relationship with genetic differences that characterize the various near‐isogenic lines. Presence of two separate dwarfing mechanisms was indicated in the material, one of them ineffective in the seedling stage.

On the Elongation of the Subcrown Internode in Barley and Wheat Seedlings

On the Elongation of the Subcrown Internode in Barley and Wheat Seedlings

INHERENT DIFFERENCES IN DEPTH OF CROWN IN WHEAT AND BARLEY

Varieties of spring wheat and barley were found to differ considerably in the length of subcrown internode and consequently in the depth of crown formation in the soil. Single plant selections within varieties showed no significant variations in depth of crown. The depth of crown appeared to be a heritable character in randomly selected lines from the cross Thatcher × Reward, the former parent tending to form deep crowns and the latter shallow crowns. Possible physiological and pathological effects of depth of crown are discussed.

Influence of temperature on the germination of Seeds : 6. Maize(Zea Mays L.)

1. The increase of the depth of sowing showed the decrease of the ratio of emergence to the amount of seeds sown and the degree of the decreasing was larger in barley than wheat. 2. The deep sowing mede the periods of the emergence of the leaves later. 3. The deep sowing made the length of the leaves and leaf sheaths longer, but these results owed to elongtion of the subcrown internodes, the actual lengths of the leaves being reduced. 4. The deep sowing gave remarkable restraint against tillering at lower nodes. 5. In case of the deep sowing over 5cm, it was found that the subcrown internode developed and the crown came up to the depth of 2-6cm.

The Relation of Depth of Planting to the Morphology of the Wheat Seedling

The subcrown axis of Triticum vulgare Vill. has been variously called rhizome, subcrown internode and mesocotyl. The term mesocotyl is objectionable for a number of reasons. It has been applied to portions of axis, which in case of oats is hypocotyl and in case of corn and wheat is It is not, therefore, applied consistently to same region of axis. Furthermore, term could be interpreted to mean between cotyledons or possibly a region between hypocotyl and epicotyl. The term should be replaced with correct terms. Normally elongated portion of subcrown axis consists of only one internode but may consist of two or more if seedings are made at depths greater than two or three inches. The fact that more than one internode may occur in subcrown axis would make term rhizome preferable, even though occurrence of more than one internode in elongated portion of axis is rare when seedings are made at usual depths. The term rhizome is commonly defined as an underground stem. From it shoots and adventitious roots may arise. This is true in case of wheat. At seeding depths greater than two or three inches rhizome frequently has distinct nodes from which normal foliage leaves, tillers and adventitious roots arise (Fig. 1). This leaves no doubt that subcrown axis is a rhizome. Normal rhizomes, in addition to elongated internode, have at least one or two other internodes, depending upon interpretation of anatomy of root-stem-transition zone of axis. At greater seeding depths there may be four or five and possibly as many as six internodes in rhizome. The literature of seedling morphology and anatomy of grasses has been reviewed by Van Tieghem (8), Bruns (2), Avery (1) and summarized by McCall (4). Avery (1) reviews briefly historical development of ideas concerning rhizome of cereals. At present time it is accepted that elongated portion of rhizome is an internode, but whether it is second or third internode remains controversial. Avery (1) considers scutellar node to be first node. According to this view elongation of wheat rhizome occurs in second internode. McCall (4) considers scutellum to be the functional cotyledon, divergent from second node. The epiblast is regarded as a vest-gial leaf and to be located at first node or root-stem-transition zone. This view holds that wheat rhizome elongates in third internode, crown developing normally at fourth node. The writer believes that McCall's evidence is convincing. In preliminary studies at Manhattan, Kansas, it has been found that depth of seeding has a marked effect on morphology of wheat seedling. This effect has been noted by Percival (6), Webb and Stephens (9) and