Chilling Damage Research Articles

The effect of various environmental factors on flowering of gladiolus. III. Temperature and moisture

Under conditions of low light intensity in winter, low temperatures (1–4°C) increase the occurrence of flower blasting. This chilling damage was observed at two developmental stages — immediately after planting and at the 7th leaf stage when spike emergence starts. Gladioli are extremely tolerant to high temperatures (up to 50 °C) as long as air humidity and soil moisture are at an optimum. The damaging effect of high temperature is generally indirect via its effect on plant water balance. Plants were directly damaged by high temperature during the period from planting to the first leaf stage. Decrease in soil moisture reduced flowering at most stages of development. The stages immediately after planting and just before spike emergence were the most sensitive.

Nucleic Acid Metabolism during Germination of Pima Cotton (Gossypium barbadense)

The nucleic acid metabolism in long staple Pima cotton (Gossypium barbadense L.) was examined during the first 48 hours of germination at 34 C. Specific activity analysis of pulselabeled nucleic acids indicated that the first significant incorporation of precursors into DNA occurs at approximately 18 hours when the radicles are emerging with a peak of incorporation occurring at 36 hours. Specific activity of total RNA also indicate peak values at 18 hours and 36 hours of germination. Sucrose gradient analysis of pulse-labeled RNA indicated that the synthesis of ribosomal RNA reached a maximum value during the 18-hour period and that there was a shift in transcriptional products during the 30- to 36-hour interval. The extraction of the RNA from pulse-chase studies and from labeled polyribosomes suggest that a significant portion of the RNA synthesized at 36 hours appears to be messenger RNA and at 18 hours is ribosomal RNA. These distinct patterns of metabolism during germination provide a background for studying nucleic acid metabolism during chilling damage.

Effects of Chilling on Protein Synthesis and CO2 Fixation in Cotton Leaves1

Biochemical changes resulting from chilling of cotton seedlings (Gossypium hirsutum L. cultivar Paymaster) that had been subjected to 5, 10, and 25 C for 36 hours were studied. Incorporation of 14C amino acids into protein and fixation of 14CO2 immediately after chilling showed a great increase in protein synthesis and CO2 fixation. When protein synthesis was determined as a function of chilling duration at either 5 or 10 C, there was an increase in the amino acid incorporation following chilling up to 48 hours, but at 72 hours there was a sharp decrease. This result indicates that severe chilling injury caused sufficient damage to the metabolism of the plant to prevent the recovery processes from occurring. The observed stimulation in protein synthesis and CO2 fixation after chilling may be related to processes associated with recovery of tissue from the chilling damage.

Some Aspects of Respiration and Respiration Inhibitors in Low Temperature Effects of the Cotton Plant

Respiration of leaf tissue from cotlon plants in the nine leaf stage was found to be severely reduced at temperatures below 15°C. In another study, young cotton plants were exposed to chilling temperature (2.8°C) for 72 hours and the ability of the plant tissues to recover respiration at normal temperatures (15 and 25°C) was examined at periodic intervals. Chilling exposures of 12 hours injured cotton tissues as indicated by increased respiratiou of leaves and roots at 25°C. Further chilling malerially reduced the capacity of the leaves to re-estahlish normal respiration rales at higher temperatures. Picolinic acid, Dexon and matonate were used to study the influence of respiratory inhibitors on the chill damage of the collon plants. The chemicals were applied six hours before cold exposure aud fhe growth and development of cold injured plants was studied to indicate the effectiveness of the treatments. Tissue weights at the final harvests indicated that picolinic acid and Dexon treated plants recovered better after cold injury than the untreated plauts. The results suggest thai 15°C may be a critical temperaliire for many physiological processes of the cotton plant because the supply of energy needed for plant reactionsis restricted due to inadequate respiration. They also indicate that the disturhances in respiration are among the early effects of chilling colton plants and may be the cause of delayed growth and development of cotton plants subjccled to non-lethal chilling exposures. It is concluded that chemicals like picolinie acid and Dexon may he effective through protection of specific systems rather than a general reduction of respiration.