The photosynthetic capacity of leaves of fruiting Capsicum plants that expanded during or shortly after anthesis remained steady throughout the growth of the fruit. The formation and growth of the fruit was associated with a reversal of the decline in photosynthetic capacity of some of the leaves that had expanded before anthesis. In deflorated plants, the photosynthetic capacity of leaves at all levels of insertion declined continuously. The variations with age of the net CO2 exchange of the leaf inserted one internode above the fruit were attributable almost exclusively to changes in intracellular resistance, while in the corresponding leaf of deflorated plants both leaf and intracellular transfer resistances were important determinants of photosynthesis. Fruiting reduced the age-related loss of soluble and fraction 1 protein and of ribulosebisphosphate carboxylase activity in the leaf immediately above the fruit. The ratio of fraction 1 protein synthesis to that of other soluble proteins in fully expanded leaves showed no tendency to decline with age in plants of either type. Intracellular resistance in fruiting plants did not appear to be linked to changes in either fraction 1 protein content or ribulosebisphosphate carboxylase activity.
In a study of the development of the second leaf of seedling wheat, the contents per lamina of fraction 1 protein and total soluble protein increased for 6 days after leaf emergence, and the contents of cytoplasmic and chloroplast rRNA for 5 days. Net synthesis of fraction 1 protein per unit of cyto-plasmic and chloroplast rRNA decreased with time. During the growth phase, incorporation of radioactive amino acids into fraction 1 protein was proportional to the amount of, rather than the rate of increase of, fraction 1 protein. After the maximum content of fraction 1 protein had been reached, incorporation into fraction 1 protein decreased both with time and relatively to other soluble proteins. The content of RNA and the proportion of rRNA found in cytoplasmic and chloroplast polyribosomes also fell. The rate of decrease in incorporation into fraction 1 protein exceeded the rate of decrease in chloroplast polyribosomes. We conclude that chloroplast polyribosomes are active in the turnover of fraction 1 protein large subunit during the growth phase, but are proportionately more active in making other proteins in older leaves.
Pressure dehydration techniques were evaluated for the collection of samples of apoplast fluid from the outer pericarp tissues of developing tomato fruit. Sap was expelled under pressure through a cannula inserted into the selected tissue of a fruit sealed in a Scholander pressure bomb. Osmolality and concentrations of K+ and hexoses were significantly lower and pH higher in sap exudates than in bulk fruit tissues. After infusion of fruit with trisodium 3-hydroxy-5,8,10-pyrenetrisulfonate as an apoplastic marker, the dye was confined to the same fruit compartment as that which yielded sap under pressure. During extended periods of sap exudation at 24�C under 1.4 MPa or more, the initial 100 μL of exuded sap was obtained without contamination from protoplasmic contents followed by a proportionate increase in sap osmolality with the aggregate volume. However, when the exuded sap was collected at 4�C under the applied pressure of 0.6-1.0 MPa, the composition of the sap remained constant with time and was independent of the applied pressure. This permits the collection of a relatively large volume of exuded fluid, up to about 500 μL sap per 70 g fruit, at an initial flow rate of 100-150 μL h-1. We conclude that the pressure dehydration technique under the described conditions allows the collection of uncontaminated apoplastic fluid from the pericarp of intact developing tomato fruit.
Thin slices cut from many plant tissues develop an increased respiration rate in the day or days after cutting (Laties 1963; ap Rees 1966). Mter slicing, the metabolism of the tissue changes in a number of respects including the capacity for salt and other solute uptake (Asprey 1937; MacDonald 1967), the relative contri-bution of the pentose phosphate shunt to total hexose catabolism !ap Rees and Beevers 1960; ap Rees 1966), and the induction of a number of enzymes (Edelman and Hall 1965; Willemot and Stumpf 1967). In the case of slices of arti-choke tissue, the presence of either indoleacetic acid or kinetin inhibits the increases, in response to slicing, of respiration, of phosphate uptake, and of invertase activity (Palmer 1966). While aspects of the latter experiments have been criticized (Vaughan and MacDonald 1967) the conclusion that the growth factors affect the response to slicing has not been challenged.
Information was sought to explain the changes with time and with osmotic stress in the rate of 14C transfer from added L-[U-14Carginine to proline in slices of tubers from Jerusalem artichoke (Helianthus tuberosus14 L.). Using osmotically stressed tubers, the transfer rates were shown to be independent of the size of the free proline pool, and of the net rate of proline accumulation. In osmotically stressed and in turgid slices, the rates of transfer increased after slicing, but decreased after 24 h. Only in freshly cut slices were the rates higher for stressed slices. Proline and hydroxy- proline in protein increased with time from slicing in both turgid and stressed slices, and proline and hydroxyproline in protein were labelled when L-[U-14C]arginine was added. However, no correlation could be shown between 14C in protein-bound proline plus hydroxyproline, and the net increase in these with time. It is concluded that externally added arginine donates carbon to proline in reactions whose rates do not determine the net rate of proline accumulation or the net rate of synthesis of proline destined for protein. The metabolism of L-[U-14C]glutamate added to discs was also studied. [14C]proline was a minor product of glutamate metabolism at all times.
Transverse slices of green banana fruit were vacuum� infiltrated with aqueous solutions of 24 potential inhibitors of protein synthesis, respiration, or ethylene production. The effects of these compounds were examined in the absence or presence of 10 p.p.m. ethylene. Of the compounds which produced marked effects mono� fiuoroacetate, 4�hydroxy�2�oxoglutarate (HKG), KCN, and cycloheximide were examined in more detail.
Banana fruit slices exposed to ethylene at a concentration of 5 �l per litre for 12 h ripened within 6 days. Slices treated with ethylene for only 6 h ripened at the same time as slices not treated with ethylene. Twenty four hours after the initiation of either a 6- or 12-h ethylene treatment, protein synthesis in pulp tissue showed similar increases. It is concluded that the increase in protein synthesis is a response to ethylene treatment rather than to ripening. Isotope dilution experiments show that radioactive valine added to pulp slices is diluted by endogenous valine before incorporation into protein. From the incorporation studies it is deduced that the ethylene-provoked increase in protein synthesis is responsible, within 24 h, for synthesis equivalent to a substantial proportion of the protein in pulp cells. Double-labelling experiments establish that the increased synthesis in response to ethylene treatment involves replacement of a large range of soluble proteins, and is not limited to the synthesis of a few specific proteins.
The involvement of RNA and protein synthesis in fruit ripening was investigated. Mature-green tomato fruits were found to contain about 30% of their ribosomal RNA in polyribosomes. At the 'breaker' or early ripening stage, about 50% of rRNA was in polyribosomes and this distribution of rRNA was maintained until fruits were fully ripe. The continued presence of polyribosomes is consistent with active protein synthesis persisting through and beyond the climacteric period when the wall-hydrolysing enzyme polygalacturonase accumulates and fruits soften, synthesize lycopene and undergo other ripening related changes. Poly(A)-containing RNA purified from polyribosomes extracted from individual fruits was used to prime the synthesis of [35S]methionine-labelled polypeptides by a wheat germ in vitro translation system. The pattern of polypeptides synthesized in response to RNA from mature-green fruits differed from that given by RNA from ripening fruits. The majority of changes were found to occur within approximately 48 h of the increase of ethylene synthesis and were apparent in all fruits with any pink or red colour. Similar results were obtained by translating total cellular RNA and total polyribosomal RNA indicating that the major RNA species shown in this study to change in abundance during ripening are polyadenylated, and hence most probably cytoplasmic, and do not accumulate as 'stored messages' outside of the polyribosomes. The differences between green and ripening fruits in polyribosome profiles were demonstrated in two cultivars of tomato. Differences in mRNA populations between green and ripe fruits were found in three cultivars.
'/%3e%3c/defs%3e%3cpath fill='%23012169' d='M0 0h10080v5040H0z'/%3e%3cpath stroke='%23fff' stroke-width='.6' d='m0 0 6 3m0-3L0 3' clip-path='url(%23b)' transform='scale(840)'/%3e%3cpath stroke='%23e4002b' stroke-width='.4' d='m0 0 6 3m0-3L0 3' clip-path='url(%23c)' transform='scale(840)'/%3e%3cpath stroke='%23fff' stroke-width='840' d='M2520 0v2520M0 1260h5040'/%3e%3cpath stroke='%23e4002b' stroke-width='504' d='M2520 0v2520M0 1260h5040'/%3e%3cg fill='%23fff'%3e%3cuse xlink:href='%23d' x='2520' y='3780'/%3e%3cuse xlink:href='%23a' x='7560' y='4200'/%3e%3cuse xlink:href='%23a' x='6300' y='2205'/%3e%3cuse xlink:href='%23a' x='7560' y='840'/%3e%3cuse xlink:href='%23a' x='8680' y='1869'/%3e%3cuse xlink:href='%23e' x='8064' y='2730'/%3e%3c/g%3e%3c/svg%3e)
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)
