Tube growth stimulation of pine pollen by low doses of irradiation. Dose rate, reproducibility and comparison between UV-light and ionizing rays

Abstract

Stimulation of the tube growth of pine pollen by low doses of UV-light or X-rays is a reproducible process, but it depends strongly of the dose rate applied. It can be proved that the observed effect is more determined by dose rate and irradiation time than by the dose itself which can vary by nearly one order of magnitude for achieving the same increase in tube elongation. The range of absorbed energy at which the stimulation effect can be observed is rather broad and overlapping between UV and X-rays. In the average the UV-energy needed is 5 times higher than X-ray energy.

Implications of ionizing radiation on pollen performance in comparison with diverse models of polar cell growth

“…Pinus silvestris pollen tube length was reduced equally to 85% by irradiation with 400 Gy at a dose rate of 0.48 Gy/sec, with 550Gy at a dose‐rate of 23 Gy/sec, and with 4,000 Gy at a dose rate of 83 Gy/sec (Zelles & Seibold, 1976). Another study shows that ID 50 for pine pollen increases from 1,060 Gy at a dose‐rate of 1 Gy/sec up to 10,000 Gy at 83 Gy/sec (Seibold et al, 1979).…”

“…Low doses of alpha‐particles (10 Gy) demonstrate beneficial effects on germination and tube growth of cotton pollen, but higher doses impose inhibitory effects (Yue et al, 2012). Several studies describe hormetic effects of low dose gamma‐irradiation on pollen of various gymnosperm (Chauhan & Katiyar, 1998; Livingston & Stettler, 1973;Seibold et al, 1979; Zelles & Seibold, 1976) and angiosperm species (Chauhan & Katiyar, 1990; Lecuyer et al, 1991; Pandey & Kumar, 2013; Yigit et al, 2009). Livingston and Stettler (1973) observed increase of tube growth of Douglas fir pollen at relatively high IR‐doses between 40 and 2,560 Gy (Livingston & Stettler, 1973; van der Donk, Livingston, Linskens, & van der Donk, 1978).…”

“…Apart from that, all other studies about gymnosperms demonstrate thresholds for stimulation below 144 Gy (Table 5), whereas higher doses caused only inhibition. Low doses (0.1–144 Gy) applied at low dose‐rates (0.005–0.5 Gy/sec) caused stimulation of Pinus silvestris pollen (Seibold et al, 1979; Zelles & Seibold, 1976). Chauhan and Katiyar (1998) observed a maximum stimulation of Pinus kesiya pollen germination (140%) and tube growth (174%) by 30 Gy of γ‐radiation (Chauhan & Katiyar, 1998) (Tables 2 & 5).…”

“…Bio‐positive IR‐effects are likewise dependent on the applied dose‐rate, as similarly reported for inhibitory effects. Increase of dose‐rate increases the threshold level for stimulation (Seibold et al, 1979; Zelles & Seibold, 1976). Accordingly, Zelles and Fendrik (1976) state that stimulation occurs by low doses applied at low dose‐rates, as well as by high doses at high dose‐rates.…”

Effects of Radiation and Growth Hormones on Pollen Germination, Pollen Tube Growth and Modulation of Radiation Responses of Pinus kesiya Royle ex Gord.

“…The radiation effects on plants could be grouped into three categories: (a) low dose irradiation usually having neither stimulatory nor inhibitory effect, (b) sub-lethal doses causing either inhibitory or stimulatory effects on various biochemical and biological processes and (c) high doses of radiation inducing maximum damage and lethality (Seibold et al 1979). In this investigation 5 Gy radiation dose therefore belongs to the (a) category while 7.5-40 Gy doses are of category (b) and doses 50 Gy and above correspond to (c) category of Seibold et al (1979), respectively. In radiation investigation pollen is considered a multitarget system (Speranza et al 1982).…”