Slender Plants Research Articles

The influence of day length on the morphology of the Halicystis parvula phase of Derbesia tenuissima (De Not.) Crn. (Chlorophyceae, Caulerpales)

Abstract Derbesia tenuissima (sporophytic stage) produced sporangia and stephanokontic zoospores in both long- and short-day conditions. These zoospores developed into Halicystis parvula plants (gametophytic stage). Zoids maintained in long-day conditions developed into complete, vesicular Halicystis plants (each composed of a spherical and a rhizoidal part), whereas zoospores maintained in short-day conditions developed into slender rhizoidal plants without a spherical part. Protoplasts extruded from “long-day” Halicystis plants in long-day conditions developed into complete plants or plants with a spherical part only; and in short-day conditions, into spherical or rhizoidal Halicystis plants, but not complete vesicular plants. Protoplasts extruded from “short-day” plants developed in both long- and short-day conditions into slender rhizoidal plants. However, in long-day conditions they obtained a vesicular form after about five weeks. Severed spherical parts of Halicystis plants and protoplasts extruded...

Growth substances and the relation between phenotype and genotype in Pisum sativum

Reciprocal grafts between plants of the tall variety Alaska and the dwarf Progress No. 9 show that neither roots nor mature leaves determine shoot phenotype. It is demonstrated that differences in stem growth between the two varieties are essentially controlled by a single Mendelian factor, and the effect of this Le locus is not graft transmissible. Combined with published data for gibberellin content this confirms that the Le locus does not control shoot phenotype by regulating gibberellin synthesis. Growth of slender plants (Le la cry (s) ) and early growth of microcryptodwarfs (le la cry (c) lm) is not inhibited by AMO-1618 at concentrations which greatly reduce growth of tall plants. This is consistent with the suggestion that rapid growth in these varieties, in the absence of the inhibitory effect of La and Cry, is not dependent on endogenous gibberellin.

The Relationships of Tetraplodon pennsylvanicus

The Relationships of Tetraplodon pennsylvanicus

Título en español.

1. The response of pineapple plants throughout their life cycle to different nutrient levels of boron in combination with different nutrient levels of calcium was studied in sand cultures. 2. Pineapple plants not receiving boron at the lowest and three highest nutrient levels of calcium, 5, 100, 250, 500 p.p.m., made much less vegetative growth than those grown without boron, but at a low calcium level, 50 p.p.m. Plants in the last group were stout and green as compared with the rather slender and light-green or yellow-green plants of the former. 3. Pineapple plants grown without boron but at the highest calcium level produced the lowest fruit yields as compared with plants grown without boron but at low calcium, 50 p.p.m. These yielded most. 4. In pineapple plants supplied with the highest nutrient concentration of boron, 5 p.p.m., yields increased as the calcium concentration of the substrate increased from 5 to 500 p.p.m. However, yields were greatest from the plants that grew at the second highest calcium concentration, 250 p.p.m. 5. Either deficient or relatively high calcium concentrations, 5, 250, 500 p.p.m., adversely and significantly affected the green weight of plants when no boron was supplied. Low-calcium plants, 50 p.p.m., produced the highest significant green weights at the lowest nutrient level of boron. 6. Increments of calcium above 50 p.p.m. at the lowest nutrient level of boron induced significant reductions in the dry weights of plants, the weights of roots, and number and weight of slips. Deficient calcium induced a similar reduction. 7. At a given boron level, total boron in the plant tissue was largely a function of the boron concentration of the substrate and was not greatly influenced by its calcium concentration. 8. At the lowest level of boron, and at the two highest calcium levels, the content of soluble boron in the tissue was considerably less than at the three lowest calcium concentrations. The least soluble or metabolically active boron was found at the highest calcium level, while the highest content of the soluble fraction of this element was accumulated in the leaves of plants grown at low calcium, 50 p.p.m. 9. The lowest yielding plants grown without boron and at the highest level of calcium, 500 p.p.m., were associated with the lowest leaf-tissue content of soluble or active boron, while the highest yielding plants grown at the same boron level, but with low calcium, 50 p.p.m., were associated with the highest content of soluble or active boron in the meristematic tissue of the leaves. 10. Increments in the calcium level did not have any marked effect on the tissue content of total boron at the highest boron level. However, soluble boron was reduced to some extent in the tissue at the two highest calcium concentrations. 11. Plants grown at the highest level of boron and at the second highest level of calcium, 250 p.p.m., produced heavier yields than plants at the same boron level, but at either lower or higher calcium levels. However, at the same boron level, increments in calcium did not definitely affect the green and dry weights of plants, the fresh and dry weights of roots, or the number and weights of slips. 12. Total calcium of the tissue was mainly determined by the calcium concentration of the substrate and was largely independent of the boron level. On the other hand, soluble calcium was unrelated to total calcium in the tissue, calcium in the substrate, or boron in the tissue.

Preliminary Investigation of Factors Determining the Growth Form of Cerastium Tetrandrum Curt

Cerastium tetrandrum Curt. is a common plant of sandy coasts and is also found inland, especially along railway tracks. Plants growirrg singly on exposed sand dunes are usually very hairy with stems closely adpressed to the substratum and with their inflorescence branches diverging widely, giving a 'dichasial angle' of about 120-150?. In the same situation plants growing very close together in a mat have ascending stems and usually much smaller dichasial angles, about 70-100?. Plants growing amongst grasses are usually taller, more or less erect, not as hairy as solitary plants and with narrow dichasial angles, about 15-35?. So striking are the differences in growth form between these plants that some taxonomists, including G. C. Druce (1920) have ranked them as sub-species, varieties or formae. This variation may be presumed to aid survival under natural conditions. The slender erect plants found among grasses seem ill-suited to existence on exposed sand dunes where the full force of the wind, together with its abrasive action (McDougal, 1913) would cause considerable mechanical damage. Similarly, the adpressed mats would be expected to suffer in competition for light with grasses and tall herbs. On the other hand, mats seem adapted to life in the exposed sand dunes where they grow and the slender erect plants to competition with their tall-growing associates. In a taxonomic investigation of these species it appeared important to determine the nature and causal control of the variation found in this and other annual British

The Flora

Plants are known only in the lower portion of the Basement Series, in a zone some 20 feet thick, which rests directly upon the Loams. But in this zone they are persistently present, and in some parts of it extremely abundant. A massive white sandstone, which has a range of more than a mile, is studded with carbonized fragments; but nearly all the determinable specimens were obtained from grey shales, which are often quite crowded with remains of slender plants. The richest of these shales are about 8 feet above the Loams, but others are only a few inches above barren yellow loam, the rapidity with which vegetable life appears being remarkable. [E. G.] Fig. 1 The following summary of the general characters of the flora is based on forty specimens:— In the grey shales are very numerous fragments of what are probably Stigmarian rootlets, one (Ar 531) showing the usual dichotomous forking of Stigmaria . In view of the absence of any direct evidence of Stigmarian axes, it would be unwise to state definitely that Stigmaria is present in these beds, although the presence of trees, in sandstones which are nearly on the same horizon and only a few yards away, make it highly probable. Lycopod megaspores are also fairly abundant in some of the samples of these shales, while the sandstones contain many large casts, one of which (Ar 593) was determinable as a Knorria -condition of ? Lepidodendron . Half embedded in a fragment of shale (Ar 530) some exceedingly

Length-factors in Pisum

From a cross of two short peas an aberrant type was obtained in F2. Plants of this type emerged from the soil in a strongly bent condition and reminded one by their further growth of etiolated, rapidly growing plants with little chlorophyll and weakly developed stipules and leaves. The rapid growth continued and resulted in very long, unbranched plants of a slender built which reached a length of 3–3.76 m. The flowerstalks were exceptionally long, the flowers of an aberrant type, caused by non-coalescence of the two parts of the keel. A considerable number of pods were parthenocarp, some produced a decreased number of seeds; pods with the normal number of seeds were scarce. This new form was called “slender” and it was shown that the characters mentioned, were caused by the pleiotrope action of two multiple factors (la and lb), both occurring recessively in the slender plants. The independent transmission of the factors La, Lb and Le could be demonstrated, the existence of linkage between lb and walso.