Inserción de péptidos en monocapas preformadas.

This experiment utilized the same two genotypes of 'Grasslands Tahora' that were used in the previously described shade and defoliation experiment (Section 5.2. 1). Stolon cuttings, of two nodes plus the apical bud with root growth initiated at the proximal node, were taken on 29 January 1 986 from a bank of clonal material of each genotype propagated in a temperature regulated glasshouse. Trays were planted with two cuttings of one of the genotypes, one at either end of the tray. Fifteen trays of each genotype were planted. Plants were allowed to establish for four weeks before treatments were applied on 25 February 1986. At this time, one of the two plants in each tray was selected for removal such that remaining plants were as uniform as was possible.

5.2.2.2 EXPERIMENTAL GROWTH CONDITIONS

Plants were grown in standard plastic propagating trays ( 40x30x5 cm) lined with paper towels and filled with 8 kg of dry quartz sand (Poutu sand; Winstone, North Shore, Auckland). Upon moistening, each tray absorbed 1 .9 1 of nutrient solution.

During the establishment period each cutting was supplied daily with 500 ml of

a nutrient solution comprising (mmo[) KN03 5.0, Ca(N03)2 1 .5 ; MgS04 1 .5 ; NaN03 2.0;

3.5, ZnS04 0.77, KCl 14.5 and (NH4)6 Mo7 024 0.0 1 6 . The sand surface in the portion of the tray without plant material was covered with aluminium foil to reduce algal growth and evaporation losses. This practice continued throughout the experiment.

The experiment was performed in the same thermostatically temperature controlled glasshouse as the shade and defoliation experiment (Section 5.2. 1 .2). Mean daily maximum and minimum air temperatures were 27. 1 ± 2.06°C (range 24.0 to 3 3 .0°C) and 1 3 .7 ± 1 .23°C (range 1 2. 1 to 1 6.3°C). Daylength decreased over the course of the experiment; 14 h 20 min at planting (29 January), 1 3 h 4 min at the beginning of the experimental period (25 February), 1 1 h 1 min at harvest ( 1 6 April).

5.2.2.3 EXPERIMENTAL TREATMENTS

5.2.2.3.1 GENOTYPE

The two genotypes of 'Grasslands Tahora' white clover used in the shade and defoliation experiment were compared.

5.2.2.3.2 PHOSPHORUS SUPPLY

The three treatment levels of phosphorus (P) supply were provided by applying nutrient solutions with P concentrations of 0.0 1 , 0.20 and 1 .0 mM. Phosphorus concentration was varied by altering the quantity of KH2P04 in the nutrient solution previously detailed (Section 5.2.2.2). All other salts were maintained at their normal strength. This procedure resulted in the potassium ( K) supply increasing from 5 to 6 mM as P supply increased from 0.0 1 to 1 .0 mM P. Plant analyses performed in conjunction with previous experimentation using this nutrient solution (Hay et al. 1 986) showed that the K content of white clover leaf DM was 3 .9% when K was supplied at 5 mM. When leaf K contents are of this order, increases in K supply are not associated with growth responses in white clover (Andrew 1 956; McNaught 1 970). Hence in this experiment it was assumed that the responses in growth that occurred with variation in nutrient supply resulted from the changes in supply of P.

On 25 February prior to application of treatment nutrient solutions all trays were leached with five successive applications of one litre of distilled water. The P

concentration in the leachate collected after the fifth water application was 0.0 1 mM P.

Then 2 1 of the appropriate nutrient solution was applied to each tray. Thereafter daily,

each cutting received 800 rnl of the appropriate treatment nutrient solution.

5.2.2.4 EXPERIMENTAL DESIGN

The trial was of factorial design with five replicates; 2 genotypes x 3 P levels x 5 replicates. A single randornised block of 30 trays was put down along one side of a glasshouse and twice a week trays were systematically rotated by moving trays two positions within the block.

5.2.2.5 MEASUREMENTS

At the time when application of P supply treatments were started (25 February 1 986) the youngest node with an unfolded leaf on the main stolon of each plant was marked with nail varnish and the stage of morphological development (Carlson 1 966a) of each partially unfolded leaf recorded. Subsequently on six occasions at approximately weekly intervals and at harvest ( 1 6 April 1 986) each plant was assessed for stage of morphological development of leaves and axillary buds at each node of the main stolon (Section 5 .2. 1 .5).

At harvest plants were cut at the marked node and the distal part of the shoot system removed after severing of any roots. The length of the main stolon (marked node to node with youngest unfolded leaf), the petiole length and leaf area of the third unfolded leaf and the diameter of the internode distal to the third unfolded leaf were measured. Leaves were then dissected from stolons and the dry weight of both components measured after oven-drying for four days at 80°C. Leaf and stolon material was then ground and the P content measured by autoanalysis after acid digestion (Williams & Twine 1 967).

5.2.2.6 ANALYSIS OF DATA

The following plant characteristics were derived from the measurements for statistical analysis; node appearance rate, position of first branching node, probability of an axillary bud initiating outgrowth and mean internode length, all relating to the main

stolon; petiole length and leaf area of the third unfolded leaf and diameter of the internode distal to it; leaf, stolon and total shoot dry weight of the plant fragment distal to the marked node and P contents of the leaf and stolon components.

The design for this experiment was balanced and data was analysed by analysis of variance using the GLM procedure in SAS (SAS Users Guide 1 988), with the Repeated Measures Option used for the analysis of the characteristics of node appearance rate, position of first branching node and probability of axillary bud initiation of outgrowth (see Section 5 .2. 1 .6).

5.3 RESULTS

5.3.1 SHADE AND DEFOLIATION EXPERIMENT